An active pattern remains in place across the center of the country with additional threats from severe thunderstorms and heavy rainfall. These concerns will remain in place through most of the weekend. An approaching storm across the Pacific Northwest is expected to bring heavy rainfall and strong winds late this weekend. The heat risk and fire weather concerns will increase across the Southwest. Read More >
Seattle, WA
Center Weather Service Unit
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000 FXUS66 KSEW 011635 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 935 AM PDT Sat Jun 1 2024 .SYNOPSIS...Weak system moving through Western Washington today. Rare late spring atmospheric river taking aim at the area beginning Sunday. Rain, heavy at times for this time of year, Sunday through Monday afternoon. Rain continuing into Tuesday but with the atmospheric river weakening rainfall amounts will be lighter. Upper level ridge building over the area Wednesday through Friday for a quick transition to drier and warmer weather && .SHORT TERM /TODAY THROUGH MONDAY/...No significant changes to the forecast this morning. The previous discussion can be found below with an updated aviation section: ...Key Messages for Upcoming Active Weather Pattern... * Late season atmospheric river pattern will develop Sunday through Tuesday. * Heavy rainfall amounts of 2-4 inches along the coast and 3-5 inches mountains during this timeframe. * Moderate to heavy rainfall of 1-2 inches across the lowlands during this timeframe. * Snow levels above 6500 feet will will promote additional runoff with several area rivers flowing out of the Cascades forecast to enter action or even minor flood stage. A Flood Watch remains in effect across portions of western Washington. Happy Meteorological Summer. Certainly not summer like weather for the next few days. Currently cloudy skies over Western Washington. Doppler radar has a large area of light precipitation covering most of the area. Surface observations reporting much of the precipitation indicated on the radar is not reaching the ground. Weak system moving through thearea this morning into the afternoon hours keeping a chance of rain in the forecast. Rainfall amounts will be light, less than a tenth of an inch. Cloudy skies will keep high temperatures only in the upper 50s to mid 60s. A little break in the action tonight with the leading edge of the approaching atmospheric river still offshore by 12z Sunday. With a 130-140 knot jet core associated with the atmospheric river there is a chance the rainfall could arrive a little earlier than the models are indicating so have added chance pops to the interior for early Sunday morning. Lows under cloudy skies in the 50s. Wet day in store on Sunday as the atmospheric river takes aim at the Pacific Northwest. Highest PWAT values moving into Oregon with 1.4 to 1.6 inch values along the Central Oregon coast but PWAT values in Western Washington are still in the 1.0 to 1.2 inch range. Air mass warming up with snow levels rising to 6500 to 8500 feet. 850 mb winds increasing during the day and by 00z Monday will be in the 25 to 40 knot range out of the southwest. This will increase the rain rates over the Olympics and Cascades. Highs will only be a few degrees warmer than the lows, a couple of degrees either side of 60. Moderate to heavy rain continuing Sunday evening until the first shortwave embedded in the flow aloft moves through Western Washington. Rainfall rates will ease overnight in the lowlands but west southwesterly 850 mb winds in the 20 to 30 knot range will keep heavier rain continuing especially in the Cascades. Snow levels remaining high so only the tops of the volcanoes will see any snow. Lots of daily rainfall records for Sunday will be in jeopardy. See climate section for more details. Another wave embedded in the flow aloft moving through Monday afternoon with rainfall rates increasing Monday morning before dropping off significantly as the system moves through Monday afternoon. Highs once again will be around 60. .LONG TERM /TUESDAY THROUGH FRIDAY/...Extended models in good agreement with one more disturbance moving through Tuesday. This feature is weaker than the first two with lower PWAT vales and weaker winds aloft. Heaviest rain along the coast and over the Olympics with lesser amounts over the Cascades and the interior. Snow levels remaining elevated with most of the precipitation in the mountains falling as rain. Models also in good agreement with an upper level ridge building quickly overt the area Wednesday and Thursday resulting in a quick drying and warming trend. By Thursday highs in the 70s will be common across the interior with highs near 70 along the coast. Some differences in the models start to show up Friday with the ECMWF continuing to keep a high amplitude ridge over the area while the GFS has the ridge further to the east with southerly flow aloft over the area. This could introduce some mid level moisture and combined with the slightly unstable air mass over the higher terrain could produce some convection especially over the Cascades late in the day. Ensemble solutions are not much help with both model ensembles supporting the operational runs. Most of the clusters supporting the drier solutions with the ridge further to the west than the GFS solution so will keep Friday dry for now with the warmer locations pushing 80 degrees. Felton && .AVIATION...Southwesterly flow aloft as the next frontal system approaches and begins to move into the region. Expect mostly VFR conditions this morning through the interior, with lowering ceilings toward the coast and northwestern portions of the area as the front pushes eastward, with rain to spread inland this afternoon and evening. KSEA...VFR conditions continue with few scattered showers. Surface winds remain northerly for now, but will become southerly as the front approaches through the day. Mostly VFR conditions continue, but occasional cigs down to around 3000-3500 can be expected at times. Ceilings will gradually lower further with increasing rain coverage late tonight after 07-10z. && .MARINE...A frontal system moving across the coastal waters this morning will move onshore and dissipate. A stronger front will approach the area waters on Sunday, bringing the next round of gusty winds to the region. Latest probabilistic guidance has a 50-70 percent chance of gusts occasionally reaching gale across the coastal waters and eastern Strait of Juan de Fuca as the frontal system moves across the area. However, guidance does not suggest frequent gusts and maintains the strongest gusts south of the coastal waters for now, so have held off on any gale watch issuance for now. Another frontal system will then move across the area waters on Monday, quickly followed by another on Tuesday for an active period. High pressure then looks to build back into the coastal waters on Wednesday. Seas currently continue to hover between 2 to 4 feet offshore this morning. Expect seas to build towards 4 to 6 feet over the weekend, before building towards 8 to 11 feet early next week. 14 && .HYDROLOGY...This could be a record breaking event for river levels around the area for this time of year. The Sunday through Tuesday forecasted rain totals are still 3 to 5 inches for the Olympics and the Cascades, with the possibility of 6 inch bullseyes along the southwest slopes of the Olympics. Snow levels will be in the 6000 to as high as 8500 foot range for most of the event. West southwesterly flow aloft favors the heaviest rainfall to be along the southwest slopes of the Olympics and the Central Washington Cascades. Right now the forecast only has only one river reaching flood stage, the Snoqualmie at Carnation with additional rivers flowing out of the Central Cascades and Southern Olympics reaching action stage. The flood stage for the Snoqualmie at Carnation is 54.0 feet. The forecast is for the river to crest right at flood stage. The Snoqualmie at Carnation has never been above 52.5 feet this time of the year. The Snoqualmie River at the Falls is currently forecast to crest under flood stage but also at the highest level it has ever been for this time of year. The flood watch for Skagit, Snohomish, King, Pierce and Mason counties remains in effect. Felton && .CLIMATE...Here are some daily rainfall records for around the area for Sunday June 2nd, Seattle 0.48 inches in 2001, Olympia 0.68 inches in 2010, Bellingham 0.48 inches in 1962, Quillayute 1.63 inches in 2010 and Hoquiam 1.35 inches in 1962. Monthly rainfall normals for the entire month of June are, Seattle 1.45 inches, Olympia 1.46 inches, Bellingham 1.61 inches, Quillayute 3.30 inches and Hoquiam 2.01 inches. It is certainly possible that some locations could surpass their normal monthly June rainfall in the first 3 days of the month. Felton && .SEW WATCHES/WARNINGS/ADVISORIES... WA...Flood Watch from Sunday morning through Wednesday morning for Bellevue and Vicinity-East Puget Sound Lowlands-Everett and Vicinity-Hood Canal Area-Lower Chehalis Valley Area- Olympics-Seattle and Vicinity-Tacoma Area-West Slopes North Cascades and Passes-West Slopes North Central Cascades and Passes-West Slopes South Central Cascades and Passes- Western Skagit County. PZ...None. && $$ 000 FXUS66 KPQR 011040 AFDPQR Area Forecast Discussion National Weather Service Portland OR 340 AM PDT Sat Jun 1 2024 .SYNOPSIS...An unseasonably strong Pacific jet stream is taking aim at the Pacific Northwest, and will lead to increasingly active weather this weekend. Today will be a bit of a transition day as high pressure aloft weakens enough to allow a weak frontal system to brush the forecast area. A stronger and much wetter system will follow for Sunday, with locally heavy rain possible along the coast and in the higher terrain. Rain will taper to showers later Sunday night, persisting through Monday and likely into Tuesday. A turn toward warmer and drier weather appears likely by the end of the week. && .SHORT TERM...Today through Monday...Latest GOES-West infrared and water vapor imagery reveals the first in a series of disturbances presently approaching the Pac NW as high pressure weakens over the region. Temperatures Friday afternoon climbed well into the 70s for the inland valleys, with a handful of locations reaching 80 degrees. The warm air mass and subsidence associated with high pressure aloft dried out the low to mid levels considerably, so this first disturbance will struggle to bring much more than a few sprinkles east of the Coast Range today/tonight. However the onshore flow and increased cloud cover should prevent anyone in our CWA from reaching 80 degrees today. For those who enjoyed the warm day Friday, at least today won`t be a total bust - NBM probabilistic guidance suggests a better than 75% chance our interior lowlands will climb into the 70s this afternoon. Overall - today will see near-normal temps and a mix of sun and clouds for most of the CWA, with the best chances of precipitation likely limited to the coast. For as normal as today is expected to be for the first day of June, Sunday will be anything but normal as a potent late-season low pressure system couples with a moderate to strong atmospheric river to bring a very wet day to SW Washington and NW Oregon. The 00z ECMWF Extreme Forecast Index (EFI) continues to suggest a high-end event climatologically, with EFI values in excess of 0.9 for most of our Cascades and a Shift-of-Tails (SOT) in the 1 to 2 range. The SOT values in excess of 1 indicate the potential for rainfall to approach record levels for this time of year. In other words, Sunday`s system will behave much more like one of our moisture-laden mid- to late-autumn frontal systems than the typical weaker systems we would come to expect in late spring. If anything, the 00z GEFS has more moisture involved with Sunday`s system, with NAEFS means solidly in the +4 to +6 standardized anomaly range for moisture transport and a return interval (in late May/early June) on the order of 10-30 years. All this points to a high-end rainfall event for early June, and one that will qualify as a significant rain event for any time of the year across our region. Perhaps the most concerning aspect of this system is the combination of unusually deep moisture with an unusually strong early June system, along with strong orographic enhancement for the Coast Range and Cascades. Fortunately, most of our rivers are starting off low or near summertime base flows, which should mitigate most hydro concerns for this event. However, the potential for extreme rainfall rates is there, especially for the higher terrain where HREF 90th percentile rain rates suggest there could be a solid 6-12 hour period with rainfall rates exceeding 0.25-0.40"/hr. This could be enough to cause some minor debris flows, especially in recently burned areas. Such rainfall rates could also cause some of our flashier creeks and rivers to jump their banks - the Grays River in particular comes to mind, but much will depend on the alignment of the atmospheric river during the peak of our event. Overall, based on NBM deterministic guidance, inland valleys can expect 1-2 inches of rain from this event through Monday night, though downsloping may hold Hood River short of 1 inch. The coast can expect to see 1.50-3.00 inches, with 2-4 inches likely for the Coast Range and Cascades. Looking at 75th percentile NBM guidance, there is the possibility for some Coast Range/Cascade locations to exceed 4 inches. This potential rings especially true after looking at the 00z HREF mean QPF, which only runs through 5 PM Sunday but already shows multiple areas in the Coast Range/Cascades exceeding 2 inches by then... with 6-12 hours still to go before the steady, locally heavy rain comes to an end. WPC suggested a marginal risk of issues due to excessive rainfall in their Day 3 outlook for 12z Sun to 12z Mon - which certainly seems warranted considering all these factors. Latest deterministic guidance brings an end to the steadier rain Monday morning as a fast-moving cold front sweeps across the Pac NW. Cool air aloft behind this system will result in plenty of showers Monday and, depending on how many sunbreaks there are, potentially even a couple thunderstorms. Sunday through Monday will see occasionally blustery S-SW winds as mixing increases and 850 mb winds occasionally push into the 40-50 kt range, though the strongest winds appear to be focusing on Sunday night based on the latest guidance. Given the potential for mixing down of the stronger winds aloft is higher than it usually is during our winter events due to the stronger sun this time of year, just about anywhere in our CWA could see 30-40 mph gusts at times Sunday through Monday. Exposed, higher elevations in the Cascades could easily see periods with W-SW wind gusts exceeding 50 mph Sunday through Monday. All in all, the weather Sunday and Monday is likely to bring the all-too- familiar "June-uary" back into our lexicon here in the Pac NW. For those who are craving more typical summer weather, you won`t have to wait long - see the long term discussion below for details on a potential heat wave by next weekend. Weagle .LONG TERM...Tuesday through Friday...Subtropical moisture remains entrained in the broader baroclinic zone stalled across the NE Pacific and Pac NW Monday night. Meanwhile, most deterministic guidance continues to depict a fast-moving shortwave being pushed toward the Pac NW on the unseasonably strong jet stream. Some models guide this system closer to the Canadian border, while others such as the 06z NAM hint at a track far enough south to bring another round of significant rainfall to at least our northern zones. Given the moisture rich environment and the recent rainfall from Sunday, this system will need to be watched closely as another shot of heavy rain Tuesday could push some drainages out of their banks. NBM median QPF for Tuesday`s system is less than 1 inch throughout the CWA, but looking upwards to the NBM 90th percentile QPF, one can see that there is some potential for higher 1-3 inch amounts for the Coast Range and Cascades north of about a Tillamook-Detroit line. Conversely, NBM 10th percentile QPF shows less than 0.25" anywhere in our CWA, so considerable variability remains. Starting midweek, models are suggesting a high likelihood of a strong upper level ridge of high pressure developing somewhere over the Western United States. Looking at the 00z WPC cluster analyses, all clusters are now indicating positive 500 mb height anomalies over WA/OR (i.e. above-normal temperatures in most cases) by Thursday. Therefore confidence in above-normal temperatures by the end of the week is very high - the challenge is in determining just how much above normal temps will be. Most 00z WPC clusters suggest the upper ridge axis will be far enough inland to maintain at least some vestige of onshore flow in the low-levels, so this does not appear to be the type of warm spell that reaches the coast. The WPC cluster most favored by ensemble members is also the hottest one, with the most significant 500 mb height anomalies. However this solution is still only shown by 40-50% of members - mostly from the EC ensemble suite - so things can still change. Unsurprisingly though, NBM probs of reaching 90 degrees for the inland valleys have increased a bit, reflecting the greater number of members showing the hot solution. As of the 07z run of the NBM, the probabilities of reaching 90 degrees in the interior lowlands were generally 30-60% for Friday and Saturday, but the probabilities of reaching 100 degrees remain below 15%. Pattern recognition-wise, this has the look of a prolonged but low-intensity heat event with multiple days in the upper 80s to mid 90s for the inland valleys. This type of heat event, while not necessarily record breaking, can still be problematic for those who are sensitive to heat. With all this in mind, those sensitive to heat should pay close attention to the forecast the next few days, and perhaps consider where they may go to stay cool late next week should the hotter forecast guidance prevail. Weagle && .AVIATION...VFR conditions prevailing, but with marine stratus along the coast for low MVFR to IFR conditions. A weak front associated with an upper trough to bring some light showers to the coast today. The marine stratus along the coast is expected to deepen later this morning and afternoon with MVFR expected to prevail. Inland areas will see variable mid and high clouds with cigs above 5000 ft. Potent for June storm approaches overnight with rain bringing widespread MVFR to IFR conditions late tonight to the coast. Along with lower cigs, visibilities likely reduced due to the rain. Inland areas likely to remain VFR but will see clouds filling in over the mountains. HREF shows about a 20-40% chance for MVFR cigs over the valley after 08Z Sun. PDX AND APPROACHES...VFR conditions expected through the entire TAF period with cigs above 5000 ft and a few sprinkles this afternoon. As the next front approaches, HREF shows a about a 20% chance for cigs near 3000 feet. Better chances for rain develop closer to 12Z Sun. Light winds in the morning becoming westerly 5-10 knots after 20Z Sat. /mh && .MARINE...A weakening Pacific front moves to the waters today and stall over the waters. A more organized and stronger storm system will move into the northeast Pacific Sunday shifting winds southerly. Small Craft Wind gusts are likely with 90+% chance of gusts exceeding 21 kts. There is a 10-20% chance for Gale Force winds of 35 kts per the NBM. But deterministic and HREF guidance have trended stronger with a 50-80% chance for gale force gusts on Sunday. At this point, gale are more likely over the outer zones (10 to 60 NM) during the day Sunday, so have issued a Gale Watch. Also issued a Small Craft Advisory for the inner zones for Sunday into Sunday evening. Will have to watch for a coastal jet to develop just as the front nears the coastline Sunday afternoon. This could result in a short period of gales to the coastline. Seas will build to 8-10 feet at 10-12 seconds Sunday afternoon, persisting into Monday. Another westerly swell will enter the waters toward the middle of next week with seas of 10-12 feet at 14-16 seconds. /mh -Batz && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...Small Craft Advisory from 5 AM to 11 PM PDT Sunday for PZZ251>253. Gale Watch from late tonight through Sunday afternoon for PZZ271>273. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland www.twitter.com/NWSPortland 000 FXUS66 KMFR 011204 AFDMFR Area Forecast Discussion National Weather Service Medford OR 504 AM PDT Sat Jun 1 2024 .Updated Aviation Discussion. .SHORT TERM...A shortwave trough will move across the area today bringing a general increase in cloudiness, slightly cooler temperatures, and breezy afternoon winds. Moisture is limited with this system, so expect dry weather. Along the coast, this trough will result in a deeper marine layer and models support a 10% chance of drizzle along the immediate coast, especially in the afternoon and evening. Northwest winds will pick up in the afternoon and evening today for most inland areas, but especially east of the Cascades and in the Shasta Valley (with gusts to around 25 mph). On Sunday and into Monday, a stronger and very moist frontal system arrives. This front is associated with a strong plume of moisture (precipitable water values of 1.5 or higher and moisture transport values (IVT) of 500-750 kg/ms). This is an unusually moist system for June. Model Extreme Forecast Index (EFI) of QPF from the ECMWF shows values approaching 1 in the Cascades to our north, but also healthy values along the Southern Oregon coast and into the Cascades. This is a strong indication that the front will be considerable for its rain production for this time of year. Precipitation will gradually move south and eastward across the area Sunday through Monday morning. Rain will begin along the coast and across much of Douglas County Sunday morning, spreading inland across areas from the Cascades west Sunday afternoon, then increasing and spreading across the area Sunday night and Monday morning. Wetting rainfall is likely for areas from the Cascades westward late Sunday through early Monday, with moderate to heavy rainfall along the coast, across the coastal mountains, Douglas County and the Southern Oregon Cascades (especially Crater Lake north). Areas that see the heaviest rain, may experience localized ponding of water on roadways, especially in urban areas or areas of poor drainage. Otherwise, expect the rain to be largely beneficial. Some showers are expected to linger Monday afternoon then taper off by Monday evening. Models continue to support storm total rain amounts of 1-2 inches along the coast, and locally up to 3 inches in some of the coast ranges. 0.50-1.50 inches of rain is expected in the rest of Douglas County and into portions of the Illinois Valley. Here in the Rogue Valley, most likely amounts will range from 0.20-0.40 of an inch. Over the Southern Oregon Cascades, rainfall totals of 0.5 to 1.5 inches is expected, mainly from Highway 140 northward. East of the Southern Oregon Cascades and from the Shasta Valley eastward in Northern California, amounts will be mostly 0.10 of an inch or less with little or nothing in southern Modoc County. As this system moves through late Sunday and Monday, gusty west winds are also likely, highest from the Cascades east. Gusts of around 20-25 mph are expected from the Cascades east Sunday afternoon/evening, increasing to 25-35 mph (and up to 40 mph across higher terrain east of the Cascades) Monday afternoon. && .AVIATION...01/12Z TAFs...VFR conditions will prevail through the TAF period for most locations. The exception being along the coast where MVFR ceilings are being observed north of Cape Blanco and into the Coquille Basin. The lower conditions will improve in the Coquille basin towards 17z as the marine stratus burns off, but it may not improve at all along the coast, north of Cape Blanco. Expect some gusty afternoon breezes, especially for inland terminals this afternoon into early this evening. -Petrucelli && .MARINE...Updated 200 AM Saturday, June 1, 2024...Calmer conditions are expected through this evening. A front will arrive on Sunday morning, bringing gusty south winds and an increasing west swell. Conditions hazardous to small craft are expected Sunday morning to areas north of Gold Beach due to increasing winds and swell. Additionally, a period of moderate to heavy rainfall is expected Sunday afternoon into Monday morning. The front will move inland Sunday afternoon, but another front is expected to move into the waters Sunday night which will result in increasing southwest winds. This front will move inland Monday morning with winds diminishing. However, westerly swell will increase during the day resulting in continued Small Craft conditions. Hazardous conditions are likely to continue through the week, though due to varying weather patterns. An upper level trough will remain to the northwest, and this will send another, heavier, longer period swell (9 to 12 ft at 12 to 14 seconds) into the waters on Wednesday. Meanwhile, the thermal trough will likely return, bringing the return of strong north winds and steep to very steep wind driven seas for the latter half of next week. -Petrucelli && .PREV DISCUSSION... /Issued 229 PM PDT Fri May 31 2024/ LONG TERM...Monday afternoon (6/03) through Thursday night(6/06)... Post frontal showers will persist through Monday afternoon, but will quickly diminish through the evening as strong ridging builds into the region behind the departing system. The model suites in previous runs have depicted the ridge well in control of the area, with steadily warming temperatures and no chances for rain throughout the extended term. The recent runs, however, have started to show a more complicated pattern, with an area of swift zonal flow, mainly lying just to our north, with ridging to the south and troughing to the north. This would keep our area mostly dry and hot, just as previously thought, although maybe not quite as warm. Also, with the zonal flow in the vicinity, a stray impulse could brush by southern Oregon, producing some light rain chances along the coast and the upper Umpqua Basin through Tuesday night. That being said, the most likely scenario remains dry. Wednesday and Thursday, the ridge builds north in response to a deepening trough upstream over the eastern Pacific. Depending on how far east that trough is, the ridge axis will remain overhead keeping the area dry and very warm for this time of year (about 10 to 15 degrees above normal), or just to our east, allowing for some southwesterly flow aloft. This southwesterly flow solution is also very warm, but typically produces a chance for convection, particularly over northern California and along and east of the Cascades in Oregon, so there is a low chance, around 15%, for afternoon thunderstorms somewhere in the area mid to late next week. Details on the timing and exact locations will need to wait until the models better resolve the situation. -BPN && .MFR WATCHES/WARNINGS/ADVISORIES... OR...CA...None. PACIFIC COASTAL WATERS...Small Craft Advisory from 5 AM Monday to 5 PM PDT Tuesday for PZZ350-356-370-376. && $$ CC 000 FXUS66 KEKA 011300 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 600 AM PDT Sat Jun 1 2024 .SYNOPSIS...Conditions in the northern areas are expected to deteriorate this weekend before a short spurt of wetting rainfalls arrives Sunday night into Monday. Southern areas will cool off but are not expected to experience any meaningful precipitation at this time. Next week, temperatures will soar to well above average from the interior to the coast, possibly reaching over 100F in some places. && .DISCUSSION...A brief weak shortwave moved by overnight. Despite a narrow area of mid to high level cloudiness, moisture was limited. Stratus and patchy fog blanketed much of the Humboldt coastal waters, and expanded well up the adjacent river valleys. The McKinleyville profiler indicates a marine layer depth up to around 2,500 feel MSL. Patchy drizzle may occur with a slightly deepening marine layer in the vicinity of Humboldt Bay this morning. Otherwise, stratus are expected to gradually lift and mix out by late morning. However, expect a partly to mostly cloudy skies as mid to high level clouds spread across the area. Temperatures today will run 5 to around 10 degrees cooler compared with yesterday`s readings across the interior, while seasonal temperatures remains along the coast. Inland highs are forecast to be in the mid 70s to mid 80`s. A last push of gusty northwest winds in Mendocino and Lake counties will occur today as the tightest pressure gradient shifts south over those counties bringing gusts to around 30 mph or locally higher on some ridge tops during the afternoon and evening. Sunday into Monday, models consistently show the track of a late- season low pressure system approaching the Pacific NW. South of that feature, a broad zone of WAA and west-southwesterly moisture flux will aid in light rain or sprinkles over coastal Del Norte Sunday morning. PWAT values are expected to increase to around 1 to 1.5 inches along the California Coast by Sunday afternoon as the frontal system sag into NW California. The 00z ECMWF Extreme Forecast Index (EFI) continues to suggest a high-end event climatologically, with EFI values in excess of 0.7 for most Del Norte County and northern Humboldt. Heaviest rain is forecast to occur late Sunday night into Monday morning in Del Norte and far northern Humboldt, as a west- southwesterly IVT plume intersects the coastal terrain. Rain rates looks to remain below 0.3 in/hr across Del Norte County. NBM probabilities range from 45% to around 60% of an inch or more late Sunday night into Monday morning those two counties. Overall this should only be a beneficial rain. Rain chances will quickly decrease farther south and east into Trinity and Mendocino counties where by the farther south portions of Mendocino and Lake counties may see no rain at all. The front will move through the entire region by Monday evening. Quickly behind this front ridging will build back over the west coast allowing temperatures to rebound quickly into the 90s and even to near or exceeding 100 degrees in Lake County on Wednesday and/or Thursday. With the expanding heat there will also be increasing heat risk in the far southeastern portion of the area, particularly near Clearlake. In coordination with the weather office in Sacramento, we went ahead and issued an excessive heat watch from Tuesday through Thursday to highlight this risk. At this time it`s more likely that only heat advisories will be needed but it isn`t impossible that warning thresholds could be reached when the heat peaks mid week. && .AVIATION...Stratus development has been isolated to the Humboldt coast, south of Orick and down to Capetown. This equates to VFR and light southerly winds at KCEC switching to a westerly prevailing wind before the afternoon. That said, stratus has developed over KACV with ceilings above 1000ft and visibility not being impacted as much. Expect MVFR to last through the morning at KACV with a few periods of IFR if ceilings dip below 1000ft, which is possible by dawn. Light southwesterly winds at KUKI this morning will see a return to gusty northerly winds by the early afternoon with VFR conditions continuing throughout. Low Level Wind Shear, LLWS, at KUKI is probable as winds mix down before the afternoon. /EYS && .MARINE...Gale force gusts have become less frequent in the southern outer waters yet, hazardous seas conditions remain as steep waves continue around 9 - 10 ft and as many seconds in period. Gusts in the low 30`s are still being reported at Point Arena as of 11z (4AM), this morning. Gusty winds and steep waves will subside by the late afternoon and remain isolated to a narrow area south of Cape Mendocino. This weekend, an upper level trough is expected to weaken the winds. Sunday a northwest swell around 10 seconds will be the main wave. Initially it is expected to be around 3 feet, but will build to around 6 feet at 10 seconds by Tuesday. Larger combined wave heights are expected Wednesday, 13 to 15 feet. /EYS && .EKA WATCHES/WARNINGS/ADVISORIES... CA... Excessive Heat Watch from Tuesday morning through Thursday evening for CAZ114-115. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 9 AM PDT this morning for PZZ450. Small Craft Advisory until 3 AM PDT Sunday for PZZ455. Small Craft Advisory until 1 PM PDT this afternoon for PZZ470. Hazardous Seas Warning until 9 AM PDT this morning for PZZ475. && $$ Visit us at https://www.weather.gov/eureka Follow us on Facebook and Twitter at: https://www.facebook.com/NWSEureka https://www.twitter.com/NWSEureka For forecast zone information see the forecast zone map online: https://www.weather.gov/images/eka/zonemap.png 000 FXUS66 KMTR 011811 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 1111 AM PDT Sat Jun 1 2024 ...New AVIATION... .SYNOPSIS... Issued at 255 AM PDT Sat Jun 1 2024 Cooler conditions today with temperatures near seasonal averages across most of the region. Warmer to hotter temperatures return Tuesday with moderate HeatRisk through the interior. && .UPDATE... Issued at 906 AM PDT Sat Jun 1 2024 Morning stratus is beginning to mix out across the northern SF Bay, the western San Mateo Peninsula, and across the Central Coast, down the Salinas Valley, and into the Gilroy-Hollister area. The marine layer has stabilized around 1200 feet at Bodega Bay and 2000 feet at Fort Ord, and stronger onshore gradients are contributing to some breezy winds across the region. The forecast remains on track with no changes at this time. Main concern continues to be the upcoming heat event beginning next Tuesday, which is expanded on in the previous discussion. DialH && .SHORT TERM... (Today and tonight) Issued at 431 AM PDT Sat Jun 1 2024 Coastal stratus and mist continue to develop due to a combination of surface to near surface cool air advection and nocturnal radiative cooling. The marine layer depth varies from 1200 feet at Bodega Bay to 2000 feet at Fort Ord. Northwest and southeast winds are juxtaposed along the coastline and inland, the northerly ACV-SFO pressure gradient is 4.9 mb, the SMX-SFO and SNS-SJC southerly pressure gradients are 1.6 mb and 2.1 mb respectively. Stratus and mist will continue developing through about sunrise then begin to mix out under diurnal surface warming as well as due to a strengthening and gusty northerly wind overlapping the immediate coastline later on today. Daytime highs today will be cooler most locations except the North Bay where downsloping winds will offset cooling. Highs today 60s/70s coastside and bayside, inland highs in the 80s. Coastal stratus redeveloping tonight and Sunday morning, lows cooling back to the upper 40s and 50s. && .LONG TERM... (Sunday through Friday) Issued at 431 AM PDT Sat Jun 1 2024 Night and morning stratus likely mixing out back to near the coastline Sunday afternoon and possibly again Monday afternoon. By late Sunday and Monday increasing amounts of water vapor will move across our forecast area, per comparison with Oakland upper air early June climatology precipitable water will reach the max moving average and may briefly exceed the early June daily maximum. Water vapor in contact with chilly sea surface temperatures favors stratus and we may also see light coastal drizzle. Beginning Tuesday the weather will then become quickly influenced by the strengthening of the subtropical high pressure system over the Pacific. The high will strengthen while sandwiched between a strong late season mid-latitude storm track reaching southwestern Canada and the Pacific NW (with a soaking rain) and the seasonally northward nudged Intertropical Convergence Zone well to our south. Global models are in better agreement with the overall motion of next week`s high pressure system, though there is some difference in the strength of the high. 850 mb temps (helpful for forecasting surface temperatures via dry adiabatic compressional warming of air parcels to the surface) vary by a couple degrees Celsius, these values are forecast to near the early June max moving average, possibly exceeding the daily maximum if the ECMWF verifies. Expect warm to hot daytime temperatures at least during Tuesday through Thursday, it`ll be hottest inland with 90s to lower 100s. At the coast there may be lingering sea-breezes though the marine layer will likely get compressed to 1000 feet or even lower, still tough to say with certainty since this is still a few days out, and the warm season maritime vs land temperature contrasts naturally keeps a thermally direct circulation potential in place. Another item to watch for, the meso to synoptic pattern may favor a southerly wind reversal either late Wednesday or Thursday. The PDO is still in a negative (cool phase). Hottest daytime temperatures this week look to be Tuesday-Wednesday with carryover into Thursday, and if the high pressure system becomes stationary then hot temperatures will carry into late week before sea breeze relief reaches inland. Though again, the global models do show potential for a southerly wind reversal i.e. sea breeze before late week. Lots of factors in the forecast next week, please stay tuned to updates. For the time being it`s a good idea to plan on at least moderate heat risk inland in our forecast area beginning Tuesday next week. && .AVIATION... (18Z TAFS) Issued at 1037 AM PDT Sat Jun 1 2024 Stratus continues to erode across the area with widespread VFR conditions expected this afternoon through the evening. Breezy to gusty winds build this afternoon with gusts generally in the 20-25 knot range. The immediate coast and KSFO are likely to see greater than 30 kt gusts. These stronger winds appear to last well into the overnight hours, but will ease in the morning. Winds aloft stay strong and more northerly overnight, leading to LLWS concerns. Stratus returns to the coast and the Monterey Bay terminals in the early night, and around the SF Bay into early Sunday. Breezy winds and widespread VFR return Sunday afternoon. Vicinity of SFO...VFR through early Sunday morning. Expect westerly winds to strengthen into the afternoon, gusting upwards of 35 knots. Winds reduce into the night but remain breezy until early Sunday morning as MVFR CIGs fill over the terminal. VFR and breezy winds are expected to return in the mid to late morning on Sunday. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...Stratus lingers at MRY and along the coast of Monterey bay. VFR returns in the afternoon as winds increase and gust around 20-25 knots. Surface winds look to reduce into the late evening and early night with MVFR CIGs beginning to move inland. However, winds aloft will stay stronger, leading to some LLWS concerns and could delay cloud cover from filling over terminals. Winds aloft reduce in the late night/ early Sunday, with IFR CIGS starting to form around that time. && .MARINE... (Today through Wednesday) Issued at 849 AM PDT Fri May 31 2024 Breezy to gusty northwest winds will continue over the outer waters into the weekend with gale force winds expected late Friday and into Saturday. This will cause a hazardous marine environment. Significant wave heights will reach up to about 11-12 feet Friday afternoon, but will begin to reduce today through the remainder of the weekend. && .CLIMATE... Issued at 127 AM PDT Sat Jun 1 2024 Record high temperatures at the long term climate stations for June 4th and 5th: Station June 4th June 5th Santa Rosa 98 in 1949 102 in 1926 Kentfield 101 in 1981 102 in 1926 Napa 102 in 1981 105 in 1903 Richmond 90 in 1955 86 in 1983 Livermore 105 in 1960 104 in 1926 San Francisco 92 in 1949 95 in 1883 SFO Airport 92 in 1955, 1949 89 in 1972 Redwood City 100 in 1981 97 in 2002, 1972 Half Moon Bay 71 in 1955 74 in 1958 Oakland downtown 96 in 1981 87 in 2002 San Jose 98 in 1904 100 in 1926 Salinas Airport 92 in 1949 87 in 1949 King City 102 in 1981, 1957 105 in 1926 && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...Small Craft Advisory from 3 PM this afternoon to 9 PM PDT this evening for SF Bay N of Bay Bridge. Small Craft Advisory until 3 AM PDT Sunday for Mry Bay. Gale Warning until 3 AM PDT Sunday for Pt Arena to Pt Reyes 0-10 nm. Small Craft Advisory until 3 PM PDT this afternoon for Pt Reyes to Pigeon Pt 0-10 nm. Gale Warning from 3 PM this afternoon to 3 AM PDT Sunday for Pt Reyes to Pigeon Pt 0-10 nm. Small Craft Advisory until 3 PM PDT Sunday for Pigeon Pt to Pt Pinos 0-10 nm-Pigeon Pt to Pt Pinos 10-60 NM-Pt Pinos to Pt Piedras Blancas 0-10 nm. Gale Warning until 3 PM PDT this afternoon for Pt Arena to Pt Reyes 10-60 NM. && $$ SHORT TERM...Canepa LONG TERM....Canepa AVIATION...Murdock MARINE...Murdock Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, Twitter, and YouTube at: www.facebook.com/nwsbayarea www.twitter.com/nwsbayarea www.youtube.com/nwsbayarea 000 FXUS66 KOTX 011758 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 1058 AM PDT Sat Jun 1 2024 .SYNOPSIS... A chance for light showers will return for the northern mountains today, but most locations will mainly only see thickening clouds and possible some sprinkles. A dynamic system pushes across the region Sunday into Monday, bringing widespread rain, followed by gusty winds, and the potential for thunderstorms on Monday. Next week will see a warming and drying trend. Confidence is increasing for temperatures warming into the 80s and 90s. && .DISCUSSION... ..DYNAMIC SPRING STORM TO BRING WIDESPREAD RAIN SUNDAY INTO MONDAY FOLLOWED BY A CHANCE FOR THUNDERSTORMS AND WINDY CONDITIONS... Today and Tonight: A weak shortwave trough of lower pressure will push across the Inland Northwest today. Clouds will increase and thicken over much of the region. Moisture will be lacking with this precursor shortwave though ahead of the "big show" spring storm system over the following 48 hours. Best chances for showers (at 30- 50%) will be across the northern mountains. Otherwise, most valley locations and the basin will largely only see the potential for sprinkles. There is a 20-25% for thunderstorms near the Canadian border today with this weak system. A westerly pressure gradient will tighten across the Cascades late this afternoon into this evening. Winds will increase into the Wenatchee Area out of the Wenatchee River Valley, on the higher benches of Wenatchee and Chelan, on the Waterville Plateau, and into the western portion of the basin; these areas will see the potential for wind gusts of 25-35 mph into the evening. Sunday through Monday night: A dynamic spring storm system remains on track to bring the potential for moderate impacts to portions of the region. There are three variables of note that will be monitored as this storm system approaches: (1) rain, (2) wind, (3) thunderstorms. A strong 150+ kt jet streak will be directed into the Northwest. The upper level trough will take on a slight negative tilt and the timing of this feature during the day on Monday could play a big role in organizing convection across the Inland Northwest. It will also bring with it a moderate strong Atmospheric River (AR 2 to 3 level event) that will be focused more so across the state of Oregon, but a good portion of the moisture will penetrate across eastern Washington and into the Idaho Panhandle. Ensembles have sped up the arrival of rainfall with the AR moving in during the day on Sunday. The earlier timing makes sense as the strong westerly jet should act to bring in the moisture plume fairly quickly. Widespread stratiform rain will be upon the region by Sunday afternoon. Strong westerly flow across the Cascades will keep rainfall amounts down in the lee of the Cascades with the focus of heavier rainfall along the Cascade crest and in the favorable upslope areas of the Idaho Panhandle (see rainfall section for amounts and probabilistic guidance). The next potential for widespread impacts will be from the winds that pick up as the rain shuts off, or becomes convective late in the morning into the afternoon and evening. The convective element with the cold front passage increases the potential for moderate impacts with winds. About 1/4 of the ECMWF ensemble members indicate the potential for 50 mph wind gusts on the Spokane West Plains and on the Palouse. This is largely due to a deep mixing layer right as the mid level cold front clears the area and the surface front moves through. Deterministic model guidance shows up to 300 J/kg of surface based CAPE as early as 10AM-12PM late Monday morning. Potential is increasing for convection to form along the cold front with 25-45 kts of unidirectional shear in the 0-6 km layer. A CAPE of near 300 J/kg with this shear profile would be sufficient for convection to organize along the cold front. There may not be a lot of lightning due to relative low Equilibrium Levels (EL) up to around 20 kft, but strong dynamics with the advancing vorticity maximum at the base of the upper level trough should be sufficient to make up for the lack of instability. The NAM is also showing around 500 J/kg of downdraft CAPE. Putting it all together and there is good potential for enhanced winds with convection that forms by late morning into the afternoon. * Rain Amounts: This is the part of the forecast where confidence is highest. Overall, precipitation accumulations have increased a bit since 24 hours prior. In general, the Cascade crest is looking at storm total rainfall of between 1.75-3.0 inches south of Lake Chelan and between 1.0-1.75 inches north of Lake Chelan. Places such as Omak, Wenatchee, and Moses Lake will see downsloping off the Cascades with much less in the way of total accumulations in the range of 0.05-0.20 inches. Rainfall amounts will then precipitously increase over extreme eastern Washington and in the Idaho Panhandle with around 0.5-1.0 inches expected for Colville, Spokane, Pullman, and Lewiston. Then between 1.0-2.0 inches expected in the Idaho Panhandle with the westerly slopes of the higher terrain likely wringing out the most moisture and may eclipse the 2 inches mark. A near certainty that the Cascade crest will see at least an inch and around an 80% chance for at least 1.5 inches. The Idaho Panhandle has a 30-60% chance for at least an inch and around a 10% chance for more than 1.5 inches. * Winds: Increased wind speeds a bit for the afternoon. Synoptically driven winds in the absent of convection are expected to be sustained 25-30 mph with gusts of up to 40-50 mph across the exposed areas of the basin. This will includes in the lee of the Cascades across the Wenatchee Area, into the Moses Lake Area, Spokane Area, Palouse, and lower Asotin and Garfield County. Winds look strong enough that a wind advisory may be needed if models continue their trend upwards over the weekend. * Thunderstorms: As previously mentioned, the potential for thunderstorms will be greatest with the surface front from late morning into the mid afternoon hours. This will be the period of the best combination of moisture, instability, and forcing -- the three ingredients need for convection. Instability will be a limiting factor, but the combination of dynamics along the cold front and aloft should be enough to overcome this deficiency. Model trends have increased the potential for organization of convection with cold front passage. * Impacts: Best potential for moderate impacts will be with any thunderstorms that develop because they will be capable of becoming organized and would enhance the potential for wind gusts at the surface. It`s possible that in this scenario that we would see 50+ mph wind gusts with confidence increase a bit for this scenario. It will be interesting to see how Convective Allowing M models (CAMs) depict this potential as we get that data for Monday on Saturday. There is the potential for moderate impacts with just the synoptically driven winds with the passage of the cold front as well. Difficult travel is expected for high profile vehicles. Winds will also have the potential for light weight objects to become airborne. See the "Hydrology Section" below for hydro impacts. /SVH Tuesday...Ensemble model guidance is in fair agreement that the Inland NW will be under zonal flow with a 120kt westerly jet poised over southern BC. The jet is also expected to push a weak system over the Cascades in the morning and into north Idaho by afternoon. This system will be much weaker than the Sunday/Monday one. It will also feature a sizable rain shadow given persistent moderate westerly flow in the mid-atmosphere. This will me especially apparent in the afternoon as moderate cold air advection develops at 700 mbs in the lee of the Cascades. Rainfall amounts will generally be a tenth of an inch or less. The instability won’t be sufficiently deep for thunderstorms, or at least it looks like that at this point. It will also remain breezy on Tuesday, however nothing like the speeds forecast for Monday. We should see wind gusts of 30-35 mph in the afternoon across portions of central Washington. Wednesday-Friday...There is very good ensemble agreement that a strong ridge will develop by midweek over the entire Western US in response to a deep trough forming between 140-150w. The result will be a significant warming and drying trend. 850 mb temperatures will climb from the 8-12C range on Tuesday to the 20-23C range on Friday. This translates to highs in the warming from the mid 60s to mid 70s on Tuesday to the 80s and potentially the lower 90s on Friday. However by Friday there are some significant model differences. Most of the GFS ensemble solutions move the aforementioned offshore trough nearly to 130w on Friday. This still results in similar temperatures, however it also introduces a small chance of showers and thunderstorms, mainly for the SE corner of WA into NC ID. Cluster analysis suggests this scenario is supported by 75% of the GFS members and around 30% of the Canadian members. Meanwhile a dry solution is supported by all of the ENS solutions. Saturday and Sunday...Model differences continue between the unsettled GFS solutions (nearly 60% of its runs), and the much drier and warmer ENS solutions. If the latter models verify it would remain dry through and very warm through the weekend. By Sunday there the models are not in good agreement. The ENS solutions have a 578 dm ridge centered over the Cascades, Canadian solutions push the ridge into western MT and the GFS runs have a much weaker ridge over central Montana. So needless to say, confidence is not high, however the majority of the ensembles support it being dry next weekend. As for temperatures there is a wide variation in solutions. The Canadian runs have 850 mb temperatures in the lower to middle 20s which would support highs in the 90s across most valley locations on Saturday with a slight cooling for Sunday. Meanwhile the GFS runs are nearly 10F cooler with an increasing chance of precipitation across the eastern third of WA and the ID Panhandle on Saturday expanding across the northern mountains and Cascades on Sunday. So stay tuned and hopefully we will see some better model agreement as we get closer in time, but right now odds favor a very warm and dry scenario. fx HYDROLOGY... There is a Hydrologic Statement in effect focusing on rises to stream, creeks, and some mainstem rivers. Base flows remain low across the region, and a good portion of the Inland Northwest is within a moderate drought (including the Cascades) and even a severe drought in the central portion of the Panhandle. Due to the ongoing drought conditions, the rain that is expected will largely be beneficial. With that said, the amount of water with a little bit of snow left to be melted in the highest elevations of the Cascades will result in a steep rise on the Stehekin River. Flooding is not anticipated at this time but will need to be monitored. Another potential impact will be for rock slides on steeper slopes in the Cascades and across the Idaho Panhandle. /SVH && .AVIATION... 18Z TAFS: An upper level trough moving through the Inland Northwest this morning is bringing widespread overcast skies and isolated spots of very light precipitation. Conditions are expected to remain VFR through the next 24 hours. There is a 20% chance for thunderstorms near the Canadian border this afternoon. Thunderstorms are expected to remain north of airports from the Methow Valley, Omak, Colville, and Sandpoint. Model soundings across northeast Washington and north Idaho keep convective cloud tops below 20kft, which may limit lightning development. Winds will pick up out of the west into KEAT Saturday afternoon and evening with sustained winds up to 15 knots and gusts up to 25 knots. FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence in VFR conditions and thunderstorms remaining north of TAF sites. ----------------------- Confidence descriptors: Low - Less than a 30 percent chance Moderate - 30 to 70 percent chance High - Greater than a 70 percent chance For additional probabilistic information for NWS Spokane airports, please refer to the Aviation Dashboard on our webpage: https:/www.weather.gov/otx/avndashboard && .PRELIMINARY POINT TEMPS/POPS... Spokane 72 49 64 52 63 43 / 20 10 50 100 90 20 Coeur d`Alene 69 48 63 51 59 43 / 20 10 60 100 90 30 Pullman 69 48 64 51 59 41 / 10 10 60 100 90 10 Lewiston 77 55 72 57 69 49 / 10 10 40 90 100 10 Colville 69 41 64 45 63 36 / 40 20 70 100 90 20 Sandpoint 66 47 61 50 57 41 / 20 20 60 100 100 60 Kellogg 68 51 61 52 56 43 / 10 20 60 100 100 50 Moses Lake 78 49 67 53 70 46 / 10 10 60 80 50 10 Wenatchee 75 54 65 54 65 48 / 20 0 70 80 50 10 Omak 75 48 67 51 69 44 / 20 10 60 80 60 10 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...None. && $$ 000 FXUS66 KPDT 011711 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 1011 AM PDT Sat Jun 1 2024 Updated Aviation Discussion .AVIATION...18z TAFs...VFR conditions expected today, with bkn-ovc cloud cover prevailing at most sites at around 10-15 kft. Winds will be moderately breezy at some sites, namely DLS and PDT, with gusts approaching the 25-30 kt range at times this afternoon, with all other sites at around 10-15 kts. Direction will generally be W/NW. A weather system will then start to move in towards the very end of the TAF period, threatening sites with rain by late tomorrow morning. Evans/74 && .PREV DISCUSSION... /issued 341 AM PDT Sat Jun 1 2024/ SHORT TERM...Today through Monday... Key Messages: 1. Breezy to windy conditions Saturday and Monday. 2. Widespread rain Sunday afternoon through Monday afternoon. 3. Thunderstorm potential Monday afternoon. Current radar and infrared satellite imagery showing some light returns approaching the west slopes of the Washington Cascades as high to mid-level clouds begin to encroach along the east slopes of the Cascades. This is associated with the approaching upper level shortwave following closely behind the departing transient ridge that brought sunny skies and warm conditions to the area on Friday. The incoming shortwave and associated weak cold front will provide rain chances along the Cascades (30-45%) and the Blues/Elkhorns (15-25%) this afternoon. The weak cold front will also allow a pressure gradient to develop along the Cascades to enhance winds through the Simcoe Highlands, Kittitas Valley, northern Blue Mountain foothills, and the Lower Columbia basin of Oregon, as gusts of 25-35 mph will be possible. Confidence in these wind values is high (80%) as the HREF suggests a 40-60% chance of wind gusts of 30 mph over the aforementioned areas, dropping to a 10-20% when increased to 35 mph. Confidence in winds reaching advisory level is low (10%) as the GFS and SREF showcase a pressure gradient of 6-7mb between Portland and Spokane, well below the normal advisory criteria of 12 mb. However, this will not be the case with the next system on Monday, as it is much more robust and may warrant the issuance of wind advisories over the Simcoe Highlands, Kittitas Valley, northern Blue Mountain foothills, and the Lower Columbia Basin of Oregon. The upper level trough and associated cold front will tighten isobars on its approach, and lead to a more enhanced gradient along the Cascades as advertised by the GFS of 11-12 mb between Portland and Spokane. Thus, gusts of 40-50 mph are anticipated to occur over the aforementioned areas peaking between 11 AM and 8 PM Monday. Confidence in these wind gusts reaching advisory level is moderate to high (70-80%) as the NBM suggests a 70-95% chance of gusts reaching or exceeding 47 mph over the earlier mentioned areas, with the highest chances (85-95%) across the Simcoe Highlands. The secondary concern resides with substantial rainfall associated with an incoming upper level trough Sunday afternoon through Monday. The moisture accompanying this system is supplied by an atmospheric river (AR), inflating precipitable water values to between 0.75"-1.25" (150-225% above normal). The AR is rather stout in nature, as the ECMWF and GFS both showcase an Integrated Vapor Transport (IVT) of between 600-800 kg/m*s, with the GFS ensemble members showing high confidence (90-100%) in an IVT of 500 kg/m*s or greater. The timing of peak rainfall has trended about 6 hours earlier with guidance over the last 24 hours, which is now expected to occur between 11 AM Sunday through 11 AM Monday. Rain amounts during this timeframe are as follows: 1.00-1.50 inch over the Cascades, Elkhorns, and northern Blue Mountains; 0.45-0.85 of an inch across the northern Blue Mountain foothills, east slopes of the Cascades, and Wallowa County; 0.20-0.40 of an inch over Central Oregon and the John Day-Ochoco Basin; and 0.10-0.20 across the Yakima/Kittitas Valleys and over lower elevations of the Columbia Basin. Confidence in these rain amounts is moderate to high (60-80%) as the NBM showcases a 70-90% chance of 1 inch or greater rainfall over the Cascades and northern Blue Mountains, a 55-75% chance of 0.50 of an inch of rainfall over the northern Blue Mountain foothills and Wallowa County, a 40-55% chance of 0.25 of an inch over Central Oregon and John Day-Ochoco Highlands, and a 40-50% of 0.25 of an inch or more over the Yakima/Kittitas Valleys and lower elevations of the Columbia Basin. These rain amounts may lead to times of moderate to heavy rainfall, especially over mountainous terrain. This may promote a rise in area rivers, which is currently only forecast to bring the Naches River near Cliffdell and near Naches to action (bankfull) stage Monday morning. Currently, forecasts only briefly peak a couple inches above action stage, but this will continue to be monitored as the event nears. The final concern associated with the passing system Sunday and Monday reside with the potential for thunderstorms to develop across the Blue Mountains and east Monday afternoon and evening. The earlier rain associated with the warm front on Sunday will help to prime the atmosphere, which should reach convective temperatures earlier ahead of the cold front on Monday. Favorable surface based CAPE values of 500-900 J/kg and shear of 30-45 kts, as advertised by the GEM and GFS respectively, provide ample parameters for isolated thunderstorms to begin to develop by late Monday morning. The main concern would reside with gusty winds, hail, and frequent lightning. This will be monitored closely over the next 48 hours as convection-allowing models (CAMs) become available. 75 LONG TERM...Tuesday through Saturday...Models continue to struggle with the pattern over the PacNW. This struggle is reflected in the EOFs varying 45-55% through the period. The main culprit of this divergence is the Gulf of Alaska upper level low. Its position and strength determines the strength and position of the amplifying upper level ridge over the area. The cluster analysis shows approximately 50-60 percent of the members build the ridge over the PacNW while 40-50 percent favor the Continental Divide. With the ridge building over the PacNW, it will be warmer and drier. If the ridge builds over the Continental Divide it will not be quite as warm with daily afternoon/evening thunderstorms over the mountains, especially Thursday onward. The ensembles show a similar pattern with the GFS favoring the Continental Divide solution while the ECMWF favors the PacNW solution. In general terms, the ECMWF has a better track record and most members (just barely) do favor the PacNW so will lean towards its solution. If the GFS pans out, daytime temperatures will be about 10 degrees cooler, but still above normal. In summary, confidence is moderate-high (60-80%) an upper level ridge will impact our weather late next week, but low (20-30%) on final temperatures and precipitation chances over the mountains given discrepancy in its position. Daytime highs will begin the period near normal but warm each day peaking Friday or Saturday 10-15 degrees above normal. As noted earlier, if the GFS pans out the mountains will see daily afternoon/evening convection beginning Thursday and continuing into the weekend. At this time, confidence is low-moderate (20-30%) that the GFS solution will pan out. Earle/81 && .PRELIMINARY POINT TEMPS/POPS... PDT 75 51 69 54 / 10 10 60 80 ALW 78 55 71 57 / 10 10 60 90 PSC 81 57 71 59 / 10 10 60 80 YKM 77 50 68 50 / 10 10 50 70 HRI 80 55 71 56 / 10 10 50 70 ELN 71 48 65 50 / 10 10 60 70 RDM 72 46 68 53 / 10 10 20 70 LGD 72 47 68 54 / 20 10 50 80 GCD 74 46 69 55 / 10 10 50 80 DLS 77 55 67 58 / 10 10 60 80 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && $$ SHORT TERM...75 LONG TERM....81 AVIATION...74 000 FXUS65 KREV 010906 AFDREV Area Forecast Discussion National Weather Service Reno NV 206 AM PDT Sat Jun 1 2024 .SYNOPSIS... Above average temperatures and mainly dry conditions will persist through early next week with a couple of weak weather systems enhancing afternoon winds today and Monday. Confidence is high in a significant warmup for mid-late next week as highs approach 100 degrees in hottest western NV valleys, with afternoon thunderstorms also possible mid to late week. && .DISCUSSION... * OVERVIEW: No major changes to the forecast. A few light showers are possible across Lassen/N. Washoe/Pershing counties Saturday afternoon and Monday. After those troughs swing by, high pressure sneaks in across the southwestern US and takes hold for most of next week. A noteworthy warm-up is in store next week because of this ridge, with lower NV valleys likely reaching into the upper 90`s, if not exceeding 100 degrees. Otherwise, for the foreseeable future it will remain sunny, hot, and dry. * CHANCES FOR PRECIP: Among the most recent CAMs (Convection- Allowing Models), there seems to be an increasing probability of some light rain across the region from US-50 northward this evening. There`s going to be a very weak and dry shortwave trough passing through today that could have just enough forcing to pop a few showers. Soundings from Lassen to Pershing counties tonight are still showing a 3km thick layer of dry air at the surface (aka inverted-V profiles, just with zero CAPE), so it looks like mostly virga. However, if we do get a slightly heavier shower, it may overcome that low-level dry air and there may be a few sprinkles of rain. Shifting to Monday: Another shortwave trough will be passing by, this time with more upper- level forcing from a stronger jetstreak. Most of the rain will be kept north of US-50 again, but this time the chance of rain actually hitting the ground will be significantly higher. As of right now these just look like quick moving, light showers. * TEMPS & WIND: There`s going to be a significant increase in temperatures next week. Lower NV valleys may hit the 100 degree mark for the first time this year while Sierra valleys will get up to the mid-80`s. The EC EFI is already highlighting Thursday through Saturday`s high temperatures as a climatologically significant event. So if you haven`t already, make sure you have working A/C and/or access to a cooling device. Even overnight lows will be relatively warm compared to the past couple weeks. As for winds, it`ll be breezy through next week with just enhanced zephyr breezes today and Monday. * IMPACTS & EXTENDED OUTLOOK: Continue to exercise extreme caution if you are recreating near fast and cold streams as hypothermia can quickly catch you off guard if you are not prepared. Also, expect rivers to have higher flows in the evening hours due to increased snowmelt during the day followed by the lag time it takes for that water to flow down down the mountain. Last but not least, we may see some afternoon thunderstorms return to the Sierra and western NV as early as Wednesday next week. As of right now, ensembles haven`t picked up on any showers next week, but over the next few days be prepared to see those PoPs increase. -Justin && .AVIATION... VFR conditions will prevail through today and Sunday. Increased winds out of the WSW on this afternoon, with gusts peaking around 25-30 kts between 20-06Z. Expect some brief light to moderate turbulence during that time as well. -Justin && .REV Watches/Warnings/Advisories... NV...None. CA...None. && $$ 000 FXUS66 KSTO 010900 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 200 AM PDT Sat Jun 1 2024 .SYNOPSIS... Slight cooldown Saturday through Monday before the return of 100s in the Valley Tuesday through Friday. An Excessive Heat Watch has been issued for the Valley from Tuesday morning until Thursday evening. Hottest temperatures expected Wednesday. Slight chance of showers for the Coastal Range Monday late morning. && .DISCUSSION... Discussion at a Glance - Cooler Saturday-Monday with increased onshore flow and Delta Breeze. - An Excessive Heat Watch has been issued from Tuesday morning to Thursday evening across the Sacramento Valley and adjacent foothills. - Areas of Major HeatRisk Tuesday for the Valley, becoming widespread Wednesday & Thursday for the Valley & Foothills with widespread triple digit high temperatures. Prepare now for elevated daytime highs and overnight lows and reconsider outdoor activities during the hottest part of the day (3:00-7:00 PM). - Moderate HeatRisk next Friday, with a few isolated spots of Major HeatRisk in the Valley; Triple digits in the Northern Sacramento Valley and adjacent Valley foothills with low to mid 90s in the Delta and Sacramento metro area Short-Term Discussion Saturday`s weather looks to give a minor reprieve with temperatures 5-8 degrees cooler than Friday ahead of our impending warm up early next week. An upper level trough is sliding over Northern CA this morning apart of a larger level low moving through the Pacific NW. This will help cool the area and keep onshore flow apart of the forecast through Monday. Afternoon highs will generally be in the upper 80s and low 90s in the Valley, with coolest temperatures expected on Monday. This weekend will be fairly quiet with generally clear skies and marginal areas of Moderate HeatRisk in the foothills and portions of the Northern Sacramento Valley. Each afternoon will see the Delta Breeze strengthen with west gusts of 15-25 MPH, tapering off through the following mornings. As the weather system moves through the Pacific NW, it will bring general cloudiness to the area and a 20-40% chance of precipitation across the Coastal Range and Southern Cascades. There is only a 15-25% chance of amounts over 0.10", so all indicators show that if anything were to develop it will be a minor amount of precipitation. Ultimately, it will remain over the mountains, keeping the Valley and much of the Sierra dry. Monday will the coolest day of the 3 day stretch with Valley highs in the mid 80s with 70s and 60s across the foothills and mountains respectively. && .EXTENDED DISCUSSION (Wednesday THROUGH Saturday)... Tuesday will see upper level ridging moving inland, increasing heights and temperatures around the region. Daytime high temperatures in the low 100s for the Valley, with widespread areas of Major HeatRisk in the Valley and extending into the foothills and portions of the Delta. National Blend of Models (NBM) probabilities of reaching 100 for the area are around 50-85% on Tuesday. Peak temperatures are expected Wednesday with the ridge firmly over the area, with hot temperatures continuing Thursday. An Excessive Heat Watch has been issued from 11 am Tuesday to 8 pm Thursday with temperatures of 95 to 107 forecasted. The Delta Breeze could bring some slightly less hot weather to influenced areas, and how strong this effect will be should become more clear over the next few days. Major HeatRisk affects everyone without effective cooling and/or adequate hydration. Consider canceling outdoor activities during the heat of the day. Clusters show there is some uncertainty between ensembles over the strength and location of the ridge late in the week. As a result the NBM has a large spread between the 25th and the 75th percentiles, which means a large range of possible high temperatures for late in the week and into the following weekend with a 10-12 degree difference in solutions. Currently widespread Moderate HeatRisk is expected for Friday, with isolated Major HeatRisk for the Valley/foothills. && .AVIATION... VFR conditions expected over the next 24 hours. Sustained surface winds under 12 kts except winds 15 to 25kts in the Delta. && .STO WATCHES/WARNINGS/ADVISORIES... Excessive Heat Watch from Tuesday morning through Thursday evening for Carquinez Strait and Delta-Central Sacramento Valley- Motherlode-Mountains Southwestern Shasta County to Western Colusa County-Northeast Foothills/Sacramento Valley-Northern Sacramento Valley-Northern San Joaquin Valley-Shasta Lake Area / Northern Shasta County-Southern Sacramento Valley. && $$ 000 FXUS65 KMSO 010816 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 216 AM MDT Sat Jun 1 2024 ...Widespread moderate to heavy rain, with rises to small streams and increased risk for rock and mudslides, Sunday night into Monday... .DISCUSSION...GOES Satellite and regional radar imagery early this morning shows a trough of low pressure moving onshore in Washington. This trough will move across the Northern Rockies by mid-afternoon, with scattered showers developing through the evening hours. The best axis of mid-level moisture and instability will set up across Idaho and Lemhi Counties and in southwest Montana, where isolated thunderstorms will be capable of producing outflow winds of 30-40 mph. An atmospheric river remains on track to bring widespread moderate to locally heavy rain Sunday night into Monday night. Ensemble forecast systems suggest Pacific moisture will reach into the 99-99.5 percentile for this time of year, with integrated water vapor transport values seeing return intervals of a once in 10 year event for early June! As with previous forecasts, the heaviest rainfall is expected across Idaho and Clearwater Counties, with probabilities of 1.00" or more of rainfall reaching 80-90 percent along the Highway 12 corridor, Clearwater Mountains, and portions of the Camas Prairie near Grangeville. Probabilities for 2.00" of more reach 20 percent south and east Grangeville and US Highway 12. Notable rises on small streams and rivers are anticipated. There will also be an increased threat for rock and debris onto roadways and in flood prone areas. Embedded isolated thunderstorms within the atmospheric river precipitation shield Sunday afternoon may lead to locally heavy rain and enhanced precipitation totals. If high end precipitation totals (2.00-3.00"+) are achieved, the risk for minor flooding will increase, particularly for small streams. Further east in western Montana, precipitation is largely anticipated to be beneficial. Most locations have a 60-80 percent chance of seeing at least 0.25" of rainfall, with the exception across southwest Montana and eastern Lemhi County where rainfall amounts will be lighter. Heavier amounts (0.50-1.00") are forecast across far northwest Montana near the Idaho panhandle, where ponding of water may occur in poor drainage areas. A strong ridge will build over the western U.S. Wednesday into next weekend, leading to an extended period of warmer, summer- like temperatures. Highs are expected to reach into the 80s to lower 90s for valleys. Ensembles continue to show uncertainty with the orientation of the ridge, thus a day or two of thunderstorms may be mixed in. /Lukinbeal && .AVIATION...GOES Satellite and regional radar imagery as of 01/0830Z shows a Pacific trough moving onshore in Washington. This trough will move across the Northern Rockies by 01/2000-2200Z, with scattered showers developing thereafter. Activity will push east of the divide by 02/0600Z. The best axis of mid-level moisture and instability will set up across Idaho and Lemhi Counties and in southwest Montana, where isolated thunderstorms will be capable of producing outflow winds of 25-35kt. /Lukinbeal && .MSO WATCHES/WARNINGS/ADVISORIES... MT...None. ID...None. && $$ 000 FXUS65 KBOI 011519 AFDBOI Area Forecast Discussion National Weather Service Boise ID 919 AM MDT Sat Jun 1 2024 .DISCUSSION...No updates to the forecast this morning. A few virga showers have developed in southern Malheur county ahead of a weak upper trough. Isolated shower/virga development will continue throughout the day, with thunder possible in west- central Idaho and far northeast Oregon. Precipitation chances this afternoon/evening are still 10-20% in our area, with the best chances over terrain. Max temps this afternoon will be 5-10 degrees above normal. The upper trough brings a very weak cold front through this evening, allowing winds to stay out of the NW overnight, with gusts 20-25 mph. Sunday will be slightly cooler before a very moist Pacific system arrives Sunday evening. This system will bring steady rain to most of the area, with chances for precipitation between 70-90% from Sunday evening to Monday evening. There is a 20% chance of thunderstorms in SW Idaho Monday afternoon, supported by unstable conditions and abundant moisture. && .AVIATION...VFR with increasing mid and high level clouds today. A slight chance of showers after 18Z, but low confidence (less than 20 percent) in any of the showers reaching terminals. Slight chance (less than 20 percent) of thunderstorms after 18Z in the West Central Mountains (including KMYL). Gusts up to 30 kt with the showers/thunderstorms. Surface winds: W-NW 5-15 kt. 10k ft MSL winds: W 10-20 kt. KBOI...VFR. SE winds less than 10 kt shifting to the northwest after 18Z. Low confidence (less than 20 percent) of a shower after 02/00Z. Sunday Outlook...VFR through Sunday afternoon. High confidence (60- 90 percent chance) of MVFR conditions developing across the north (KBKE-KMYL) associated with widespread rain Sunday night. SW-NW winds 5-15 kt with local gusts to 25 kt. && .PREV DISCUSSION... SHORT TERM...Today through Monday night...Models have been consistently showing marginally moist/unstable support for showers across SE Oregon and SW Idaho this afternoon and evening ahead of a weak upper trough. Confidence is low, therefore pops remain generally less than 20 percent. There is also less than a 20 percent chance of thunderstorms in central Idaho this afternoon. Some of the high resolution guidance indicates wind gusts up to 35 mph with the showers/storms. A weak cold front slides through the region tonight. Wind gusts up to 30 mph accompany the front. Dry conditions in a post-frontal regime are anticipated on Sunday, along with slightly cooler temperatures. A very moist Pacific system is still on track to spread rain across the area Sunday night and Monday. Latest model runs are a bit faster and further south with the heaviest rainfall. Highest total amounts (> 1 inch) are likely (>60 percent chance) across portions of central Idaho, including the Boise/West Central Mountains. There is also a marginal risk for flooding in these areas per latest WPC Outlook, but confidence is low. Forecasts do show some rises on mainstem rivers in central Idaho after the rain event during the midweek, but no forecast points get anywhere close to flood stage. There is also a 20 percent chance of thunderstorms in SW Idaho on Monday. Temperatures will be much cooler, along with breezy to locally windy conditions. LONG TERM...Tuesday through Saturday...Models, including the ensembles, continue to indicate a substantial pattern change to hot/mostly dry conditions later in the week as an upper ridge strengthens over the region. Temperatures warm from near normal on Tuesday to 15-20 degrees above normal Thursday through Saturday. Enough moisture could make it into our area for a slight chance of showers (generally less than 20 percent) late in the week. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...None. OR...None. && $$ www.weather.gov/Boise Interact with us via social media: www.facebook.com/NWSBoise www.twitter.com/NWSBoise DISCUSSION...JM AVIATION.....TL SHORT TERM...BW LONG TERM....BW 000 FXUS65 KLKN 010857 AFDLKN Area Forecast Discussion National Weather Service Elko NV 157 AM PDT Sat Jun 1 2024 .SYNOPSIS... Warming trend continues across the Intermountain West today. Over the next few days, a couple of disturbances are forecast to pass through the Silver State. This will lead to a chance of afternoon showers and thunderstorms, breezier conditions, and a moderation of the warming trend through early next week. By the middle to end of next week, a building ridge of high pressure will lead to an appreciable warming trend, sending afternoon highs into the 90s. && .SHORT TERM...Saturday and Sunday. Blended model guidance continues to advertise afternoon highs trending upwards a few degrees over yesterday. We`ll be looking at high temperatures ranging from the upper 70s to mid 80s across the district. A weak impulse will generate some lift across the Nevada today, which will lead to a chance of isolated showers later this afternoon in eastern Elko and White Pine Counties. Any shower that forms is projected to end during the evening hours. Additionally, a west to east pressure gradient will form in response, which will lead to an uptick in westerly winds by afternoon. Gusts in the 25-30 mph range will be conceivable through the evening hours. Afternoon highs trend downward a couple degrees on Sunday in due to the upper disturbance making its way further through the Intermountain West. The lift/vorticity associated with this system on Sunday will be east of the forecast area, so dry weather is the most likely scenario through the daytime. However, the gusty conditions are forecast to continue, with gusts again peaking out around 25-30 mph in the late afternoon and evening hours. By the late Sunday night, a more substantial trough of low pressure will begin influencing weather across the district. Isolated showers late Sunday night cannot be entirely ruled out in northern Humboldt County ahead of this trough of low pressure. .LONG TERM...Monday through next Friday. Monday, an upper level trough will move across portions of the Pacific Northwest leading to gusty westerly winds 25-35 mph, with scattered to numerous showers mainly north of and including I-80. During the afternoon in addition to the scattered to numerous showers, some isolated thunderstorms may pulse up across northern Elko county and into southern Idaho. Temperatures will be in the upper 70s to low 80s, with lows in the mid to upper 40s for most. Tuesday through some of Thursday, dry conditions prevail as a ridge builds into the area. This will lead to above average temperatures in the 90s Wednesday through Saturday. Some moisture moves under cuts the ridge allowing for some isolated shower chances across northern Nevada Thursday afternoon. Friday and into the weekend the ridge begins to break down ahead of an incoming trough. This will lead to some more shower chances, all north of I-80. && .AVIATION... .AVIATION...VFR conditions will continue through the next 24 hours at all terminals. Winds this afternoon become westerly 10-15kts gusting to 25kts over most of the region. && .HYDROLOGY...Flows on many small creeks and streams remain elevated. The lower Humboldt continues to run strong with Battle Mountain currently in action stage and is expected to remain there for the next several days. Wildhorse Reservoir resides in action stage and is forecast to remain in action stage for the next several days. Finally, Lamoille Creek will be hovering around action stage for the next couple days and may even increase slightly as temperatures slowly climb higher in the afternoon period. && .LKN Watches/Warnings/Advisories... None. && $$ 95/91/96 |
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