000 FXUS66 KSEW 210336 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 836 PM PDT Mon Mar 20 2023 .UPDATE... Evening forecast is on track with areas of showers continuing across the region. Models continue to depict a drying trend from south to north especially after midnight tonight, but will continue chances of rain across most of the forecast area in the overnight hours. Amounts have been primarily less than 1/4" of rain today, and many areas even less than a tenth of an inch. Exception being the mountains where 1/4-3/4" of rain totals have been observed in the past 24 hours. Temps currently very uniform in the lowlands between 45-50 degrees and with clouds overnight do not expect much more cooling, so readings are lightly to stay slightly warmer than normal overnight. && .AVIATION...Mix of ceilings and visibility across the region as a broken line of showers continues to lift across the area this evening. With showers becoming less widespread, expect general trends toward improving ceilings. Local reductions likely remain under showers that linger. Winds generally southerly this evening, but becoming northerly for the interior terminals late tonight/early Tuesday. Expect lower stratus deck to redevelop for MVFR ceilings (local IFR) overnight through Tuesday morning, with fairly quick return to VFR Tuesday morning after daybreak. KSEA...Southwesterly surface winds with showers near the terminal through this evening but showers should dissipate as the night progresses. Expect ceilings right around 3000 ft for the next few hours, continuing to trend broken and some slight lifting through evening. However, lower MVFR stratus deck likely returns overnight through Tuesday morning. Surface winds likely become northerly after 14z Tue through the remainder of the period. Cullen/McMillian && .MARINE...A weak disturbance has pushed inland this evening. Following that, weak high pressure follows Tuesday into early Wednesday, with breezy northerlies boosting winds to around 20 kt later in the day tomorrow. A stronger push of west winds arrive later Wednesday through the Strait of Juan de Fuca as the upper trough passes. A stronger weather system then arrives late Wednesday night into Thursday as stronger southerlies arrive ahead of a front. This will likely require the issuance of small craft advisories for winds with this system. Meanwhile, seas over the coastal waters will hold around 4 to 7 feet through early Thursday, but sharply build above 15 ft Friday. Cullen/McMillian && .PREV DISCUSSION... /issued 217 PM PDT Mon Mar 20 2023/ SYNOPSIS...A few showers will linger across Western Washington into early Tuesday as a broad upper trough remains over the region. Weak high pressure aloft will produce drier conditions Tuesday afternoon into Wednesday. A trough digging southward in the Gulf of Alaska will push a cold front into the region on Thursday. Another upper trough will produce unseasonably cool and unsettled conditions into next weekend. SHORT TERM /TONIGHT THROUGH THURSDAY/...Scattered showers continue across the area this afternoon as a broad upper level trough gradually shifts eastward across the Pacific Northwest. Most of the showers will begin to wane by this evening with the exception of some possible weak convergence zone activity over Snohomish/Skagit counties lingering into the early hours of Tuesday morning. Weak upper ridging shifting southward over the interior of British Columbia will dry things out across Western Washington Tuesday afternoon through much of Wednesday. Increasing onshore flow Wednesday evening could generate a few convergence zone showers. An upper trough digging southward in the Gulf of Alaska will take a more northern track than that of previous systems during the later half of the week. This will send a more organized frontal system into Western Washington during the day on Thursday. Model agreement remains fairly consistent with this timing. A round of gusty winds, lowland rain, and mountain snow are expected. Advisory level snow amounts look probable in the passes. LONG TERM /FRIDAY THROUGH MONDAY/...The trailing upper trough will shift onshore on Friday. Snow levels could dip to 500 to 1000 feet during the night and morning hours, but impactful accumulation in the lowlands is not expected. Cool, showery conditions will prevail Friday into Saturday with the upper trough over the area. Ensemble cluster plots show more uncertainty in the forecast by the beginning of next week. Another upper trough is expected to dip southward over the NE Pacific during the period, but model solutions with the track vary considerably. 27 AVIATION...Mix of ceilings and visibility across the region as a broken line of showers continues to lift across the area this afternoon. With showers becoming less widespread, expect general trends toward improving ceilings with many terminals VFR after 23z. Local reductions likely remain under showers that linger. Winds generally southerly this afternoon and evening, but becoming northerly for the interior terminals late tonight/early Tuesday. Expect lower stratus deck to redevelop for MVFR ceilings (local IFR) overnight through Tuesday morning, with fairly quick return to VFR Tuesday morning after daybreak. KSEA...South surface winds with a showers near the terminal through early afternoon. Expect ceilings right around 3000 ft for the next few hours, continuing to trend broken and some slight lifting through evening. However, lower MVFR stratus deck likely returns overnight through Tuesday morning. Surface winds likely become northerly after 14z Tue through the remainder of the period. Cullen MARINE...A weak low remains to the south of the area over the Oregon coastal waters this afternoon, and it will slowly advance inland through the remainder of today with a decaying front pushing onshore across the local waters. Weak high pressure follows Tuesday into early Wednesday, with breezy northerlies boosting winds to around 20 kt later in the day tomorrow. A stronger push of west winds arrive later Wednesday through the Strait of Juan de Fuca as the upper trough passes. A stronger weather system then arrives late Wednesday night into Thursday as stronger southerlies arrive ahead of a front. This will likely require the issuance of small craft advisories for winds with this system. Meanwhile, seas over the coastal waters will hold around 4 to 7 feet through early Thursday, but sharply build above 15 ft Friday. Cullen HYDROLOGY...No river flooding expected over the next 7 days. && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...None. && $$

000 FXUS66 KPQR 202144 AFDPQR Area Forecast Discussion National Weather Service Portland OR 243 PM PDT Mon Mar 20 2023 .SYNOPSIS...Dry weather tonight through at least Wednesday morning low-level flow temporarily turns offshore. The latter part of the week and into the weekend will be fairly wet as a as series of systems move across the region bringing precipitation. Thursday night into Friday morning, snow levels drop down to around 500 to 1000 ft and bring the possibility of snow to the valley floor. Precipitation will continue, with a slight warming trend expected through the weekend. && .SHORT TERM...Tonight through Thursday..Satellite and Radar imagery continue to show showers moving eastward across the region as a surface meso-low continues to slowly move onshore this afternoon. As the center of the low dissipates, expect showers to decrease through this evening. These showers look to be the last bit of precipitation for the next 24 to 36 hours or so as a very sloppy, upper level shortwave, which is embedded within a very broad upper level trough builds over the region. This will maintain the overall warming trend that is indicative of spring along with some dry days. However, this will likely be short lived as winter will attempt to give a last hurrah Thursday/Friday. WPC cluster analysis for 500 mb heights and anomalies continues to show very strong agreement amongst models and their ensembles for upper level troughing and below normal heights over the western CONUS from Wednesday through Saturday. Tonight into Tuesday morning, clear skies, cool temperatures, minimal winds and a very moist ground will create the optimal environment for patchy fog/frost development. HREF guidance is showing a strong signal (30-50% probability) for visibilities below half a mile primarily along and west of the I-5 corridor. While other areas aren`t being highlighted by this guidance, experience points towards the potential development in other places. There is also the possibility that some areas frost out, rather than fog in. Therefore am keeping both patchy fog and patchy frost in the forecast for most of the majority of the Willamette Valley. Any fog/frost that does develop overnight should quickly dissipate by early Tuesday morning. Tuesday and Wednesday, warm and dry conditions are expected. With daytime highs in the upper 50s to low 60s for the Willamette Valley, in the low to mid 50s along the coast, upper 40s to low 50s for the Coast Range and in the mid 40s to mid 50s for the Cascades. However, models and their ensembles are in good agreement that by Wednesday morning/afternoon the backside of the aforementioned, broad upper level trough will bring slightly cooler air and precipitation back into the forecast. This will be swiftly followed by a much stronger system Thursday night/Friday. .LONG TERM...Thursday night through Monday... As stated above WPC cluster analysis shows very strong agreement for upper level troughing and below normal heights over western CONUS throughout the long range forecast period. This means that cooler weather is favored with daytime high temperatures generally in the low to mid 40s for most of the CWA with the exception being the Cascades where daytime highs will likely be in the 30s. As alluded to in the above discussion, Thursday night into Friday, there is a possibility for snow to return to the forecast as 850 mb temperatures around -5C to -7C. This is a signpost that snow could be seen on the Valley Floor during that time. This system also looks to have a good amount of moisture as well. This means that while the valley floor could see a dusting, higher elevations like the Coast Range and the Cascades see significant new snow accumulations. At this time the Coast Range could see 1 to 3 inches of new snow and the Cascades could pick up new snow around 6 to 8 inches with the possibility more as some models are showing up to 12 inches of accumulation. Continue to monitor the forecast as this could change and Winter Weather headlines could be issued within the next 24 hours. Saturday, Sunday and Monday the low which would bring the cold and wet weather mentioned above, is expected to slide southward paralleling the Pac NW coast line as it dive down towards California. This will keep colder temperatures in the forecast, but allow for dry air to filter into the region. /42 && .AVIATION...00z TAF preliminary thoughts: MVFR conditions continue to dominate much of SW Washington and NW Oregon today, though there are areas of IFR and VFR interspersed. Low pressure moving onshore will likely maintain MVFR cigs for most into this evening, though there will be a gradual clearing trend from south to north. While forecast models continue to suggest most of the district being VFR by 06z, suspect this is a tad aggressive based on latest satellite trends, and that the clearing will occur a little slower than what these models suggest. Valley fog may try to form late tonight/Tue morning if skies sufficiently clear. 12z HREF probabilistic guidance suggests a 50-70 percent chance of IFR/LIFR fog developing for the Willamette Valley terminals between 11z-17z Tue. Our forecast is a little more conservative than this, as lingering clouds may hinder fog development overnight. The Oregon coast will likely clear out tonight as flow turns increasingly offshore, though KAST may hold onto some clouds through Tue morning due to their proximity to the departing low. North winds will increase Tuesday, with gusts 20-30 kt possible south of the Columbia River. For detailed Pac NW aviation weather information, go online to: http://weather.gov/zse KPDX AND APPROACHES...Mainly MVFR with widespread showers through 00z Tue, with S-SW winds gusting 15-25 kt before diminishing this evening. Skies will gradually clear this evening, raising the potential for fog to develop by sunrise. Latest forecast guidance suggests roughly a 70% chance of IFR/LIFR fog forming sometime between 10z-17z. VFR conds would likely return by 17z.Weagle && .MARINE...Compact low pressure near the mouth of the Columbia River will continue to weaken while drifting onshore this evening. Winds and seas associated with this low were a little weaker than anticipated, so it appears to have been a good call by the night shift in lowering the Hazardous Seas Warning to a Small Craft Advisory. Seas are barely touching SCA criteria at Buoy 46050 (8 ft/9 sec), and seas are generally 5-6 ft north of Cascade Head. Therefore we will drop the SCA for today. Low pressure moving into California will draw increasing northerly flow across the waters, with gusts as high as 30 kt possible by late Tue afternoon. We will be issuing a SCA for all waters (except the Columbia Bar) Tue afternoon into Tue night to handle this. These northerlies will decrease Wed as the low continues on into the Great Basin. Active weather looks to return Thursday as a fast moving cold front from the Pacific sweeps across the Pac NW. The fetch behind this frontal system suggests seas could reach well into the teens by Friday morning. Indeed, the NBM 90th percentile wave heights approach 20 ft at their peak Friday morning. Weagle && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...Small Craft Advisory from 2 PM to 11 PM PDT Tuesday for Coastal waters from Cape Shoalwater WA to Cape Falcon OR out 60 NM. Small Craft Advisory from 11 AM to 11 PM PDT Tuesday for Coastal waters from Cape Foulweather OR to Florence OR out 10 NM. Small Craft Advisory from 11 AM Tuesday to 5 AM PDT Wednesday for Coastal waters from Cape Foulweather OR to Florence OR from 10 to 60 NM. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland www.twitter.com/NWSPortland

000 FXUS66 KMFR 210332 AFDMFR Area Forecast Discussion National Weather Service Medford OR 832 PM PDT Mon Mar 20 2023 .DISCUSSION... Conditions tonight could favor fog in sheltered valleys including the Illinois and Umpqua Basins. The mostly clear skies tonight will lead to temperatures in the teens east of the Cascades and below freezing elsewhere, besides the coast. The coast could see temperatures falling to the mid-30s tonight with isolated spots of frost, so have decided against issuing a Frost Advisory for the limited areas. A light breeze returns areawide tomorrow afternoon under mostly clear skies. Rain/snow chances return mid-week with more active weather later this week. See the previous discussion for more details. -Hermansen && .AVIATION....AVIATION...21/00Z TAFs...There is VFR across the area this evening. Tonight, KOTH will maintain VFR conditions, but the end of the TAF period will include stronger winds with gusts nearing 20 to 25 kt. There is an outlier of the GFS that has stronger winds, but a majority of guidance has lower winds that are in the KOTH TAF. RBG will keep VFR conditions until the early morning. At KRBG between 11Z through 16Z MVFR is likely with a decrease in visibility. This could mean either a lower cloud deck or fog, and more information will come in the upcoming TAFs. Areas of fog are likely in the more sheltered valleys like the Illinois and Umpqua Basin tonight. The Rogue Valley, including KMFR, however, should remain VFR as northeast to east winds keep the valley well mixed. East of the Cascades, expect mainly VFR conditions. However, guidance supports a slight chance for low clouds developing at KLMT in the early morning hours. Confidence is low on this and have leaned towards keeping VFR in for KLMT. -Hermansen/CC && .MARINE...Updated 800 PM PDT Monday, March 20, 2023...Winds will become north to northeast tonight. Steep seas will persist this evening , then briefly improve tonight into early Tuesday morning. After this brief period of improved conditions, northerly winds increase as low pressure moves inland to the south of the region and into central California. This will bring the return of steep seas by Tuesday morning, with very steep and hazardous seas possible south of Coos Bay by late Tuesday afternoon. Winds are expected to remain just below gales for most areas. However, winds could briefly reach gales early Tuesday evening, especially for areas from Gold Beach south. Conditions improve Wednesday afternoon into Wednesday night as winds ease seas briefly diminish. There will be another brief break in conditions late Wednesday night into Thursday, but, another system passes through the region on Thursday. This will bring another round of gusty south to southwest winds along with an increase in wind driven seas. In addition, a heavy, long period northwest swell (13-15 ft @ 14-15 seconds) will follow late Thursday into Friday. This will maintain steep to very steep seas through the end of the week and into the weekend. -BR-y/CC && .PREV DISCUSSION... /Issued 249 PM PDT Mon Mar 20 2023/ SHORT TERM... Partly cloudy skies with plenty of snow on the ground is evident on satellite this afternoon. We`ll see some high pressure build in as we move past this Spring Equinox earlier this afternoon. Fog seems unlikely in many of the large valleys this evening given the current dewpoints and anticipated low temperatures. If fog does form, Grants Pass always seems the most likely area to produce fog, yet dewpoints sit at 25 during max mixing . Anyways, frost seems more likely tonight given the lower dewpoints below freezing. By Tuesday morning, 500 mb level heights will begin to break down as a strong low approaches the central California coast well to our south. Over Oregon, low level flow is out of the east between 2000 to 5500 feet above seal level. This should keep things on the drier side in our region early on. However, the approaching low will bring some precipitation to the region by Tuesday evening. Impacts are anticipated to be limited to none at all within Modoc and Siskiyou County. Even in a worst case scenario, 6 inches of snow is the most anticipated over the Warners near Cedar Pass. To produce this, we would have to see a more northerly trajectory in the low path and a wetter system, both not currently anticipated for our region. More upper level energy will move into the forecast area by Wednesday afternoon, although this will have significantly less power than what is expected to hit California Tuesday. This wave of energy has a 60 to 90 percent chance to bring precipitation to the region with some light snow above 3000 to 3500 feet. Overall, the cool active weather pattern continues to kick spring off. However, impacts to society at large are not anticipated over the next few days. That might chance with the Thursday system, which is discussed below. -Smith Long Term...Thursday (3/23) through Monday (3/27)... A trough will dig into the region from the northwest Thursday. This will be the beginning of a cold and wet pattern for the forecast area, under general troughing and northwest flow aloft. When a very similar pattern occurred back towards the end of February, we built significant snowpack and spent many days under showers. We also had daily occurrences of valley snow west of the Cascades, and with the latest model runs trending colder, we could very well see the same again here in late March. The long term forecast features these cooler temperatures. It also keeps a chance of precipitation through every day, although those chances increase when any shortwaves or major trough axes swing through, which look most likely Thursday and again Monday. Meanwhile, snow levels are expected to hover around 1000 feet overnight and around 2500 feet during the day. There is still a lot of spread in the models regarding details of intensity and timing of precipitation. These details will become more apparent over the next several forecast cycles, but as of now we can say it does look like cooler and wetter weather will be the rule throughout the extended term. -BPN && .MFR WATCHES/WARNINGS/ADVISORIES... OR...CA...None. PACIFIC COASTAL WATERS...Small Craft Advisory until 11 PM PDT this evening for PZZ350-356-370-376. Hazardous Seas Watch from Tuesday afternoon through Wednesday afternoon for PZZ350-356-370-376. && $$

000 FXUS66 KEKA 202255 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 309 PM PDT Mon Mar 20 2023 .SYNOPSIS...Wrap around rain and mountain snow showers will spread into the area Tuesday and Wednesday. Another trough will bring additional beneficial rain and mountain snow Thursday through Friday. A colder storm will likely impact the area with more beneficial rain and snow late this weekend or early next week. && .DISCUSSION...A nice break from the rainy weather today with a shortwave ridge promoting subsidence and clearing skies. With a cooler post frontal airmass and clearer skies comes the potential for frost in the interior valleys tonight. Clouds in advance of the next storm brewing offshore west of 130W will start to spread over the area later tonight. This will counteract the longwave cooling and reduce the risk for frost. National Blend of Models and legacy guidance has temperatures falling into the mid 30`s for a couple of hours or so before cloud cover becomes too thick and precipitation starts to fall across interior Mendocino and Lake Counties early Tuesday morning. Thus, we hoisted a frost advisory for interior Mendocino and northern Lake counties. The window for frost will close quickly early Tuesday morning once precipitation begins. Coastal areas could also have some frost early Tuesday morning, especially as drying easterlies develop toward morning. The east winds will also produce downslope warming in exposed locations. Otherwise, the brunt of the next storm will head southward into central and southern California Tue. Wrap around precipitation will spread into the area on Tuesday, with the highest amounts of rain and mountain snow for Lake and southern Mendocino Counties. Snow level guidance continues to indicate snow above 3500 feet in the morning which is above the major highway passes in NW CA. Some light snow or flurries may occur in the morning down to 2500-3000 feet, however accumulations are not expected to have a major impact. Northerlies and northeasterly winds will also ramp up as a compact surface low develops offshore central California. We will see some gusty winds over the ridges and perhaps coastal headlands. The models have been inconsistent with the magnitude of northerly winds nearshore and for now we opted to follow the blended guidance. An advisory for wind does not appear to be necessary at this time. We will likely see another uptick in precipitation coverage, intensity and frequency Thursday through Friday as another transient shortwave trough embedded in the westerly flow heads into the Pacific Northwest. Snow impacts will be on the rise for the west facing slopes of Del Norte, Humboldt and Trinity Counties as early as Thu night. Travel on highways 299 and 36 may be impacted with 2-4 inches of snow above about 2500 feet late Thursday or early Friday morning. Light snow will be possible from 1500 to 2500 feet, but impacts will be minimal. The upshot is this storm looks to move through quickly and precipitation intensity and frequency should diminish over the weekend. Model divergence and discrepancies grow with a large cold trough digging southward offshore over the weekend into early next week. About 50% of ensemble clusters support a 500mb pattern that would yield significant snow accumulations for NW California. Blended guidance shows quite the ensemble range for elevations between 2500 to 3000 feet. There is still a great deal of variability and uncertainty 6 to 8 days out and a lot of details still need to be ironed out. Overall more beneficial rain and mountain snow is expected into early next week. It will also get colder for latter March and frost and freeze concerns will increase. && .AVIATION...MVFR ceilings eroded into the late morning while surface winds remain light. Mid to high clouds will wrap around low pressure working its way SE overnight. Dry, surface offshore flow will aid in maintaining VFR criteria at ACV and CEC. Light precipitation will eventually drive northward early Tuesday morning, with the best coverage of rainfall at UKI. ACV may see brief light drizzle or showers, which may develop brief MVFR conditions. Ceilings will remain VFR for the most part, with UKI to see some MVFR levels with the precipitation. Northerly winds will increase throughout the day on Tuesday. && .MARINE...A brief lull in winds and seas in underway. By early Tuesday, a strong surface low moving into C. CA will cause northerly winds to quickly strengthen to gale strength in the outer waters. The exact strength and position of the surface low as it moves in is still undetermined, but confidence was high enough to launch Gale Warnings for the outer zones. The gale will be maintained until early Wednesday morning while steep, hazardous seas are generated. A burst of these seas is expected to be delivered into the Northern Inner zones Tuesday night through Wednesday morning. Winds will begin to ease early Wednesday morning. A NW swell will build in on Friday to the low to mid teens. && .EKA WATCHES/WARNINGS/ADVISORIES... CA... Frost Advisory from 1 AM to 6 AM PDT Tuesday for CAZ109>111- 114-115. NORTHWEST CALIFORNIA COASTAL WATERS... Hazardous Seas Watch from Tuesday evening through Wednesday morning for PZZ450. Gale Warning from 1 PM Tuesday to 4 AM PDT Wednesday for PZZ470-475. && $$ 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 210549 AFDMTR Area Forecast Discussion National Weather Service San Francisco Bay Area 1049 PM PDT Mon Mar 20 2023 .SYNOPSIS...High winds and widespread rainfall tomorrow, with High Wind Warnings out for the Monterey and San benito mountains and Wind Advisories from the San Francisco Bay Area to the Monterey County coast. Scattered showers persist into Wednesday and unsettled pattern continues into next week. Monitoring potential for unseasonably cold temperatures next weekend, and a new storm system the beginning of next week. && .DISCUSSION...as of 08:49 PM PDT Monday...A few notable shifts among high res guidance this evening helps to bring a little more confidence in the forecast. At this point, it seems likely that the surface low will move into the coastal region very near the SF Peninsula. A low coming onshore in this location would still keep the highest winds to the south of the Bay Area proper, though with antecedent conditions, still expect impacts due to downed trees and power lines across the Bay Area. For now, kept the Bay Area and surrounding coastline under High Wind Advisory, while upgrading the Big Sur Coast, southern Monterey Bay, and northern Salinas Valley to be included in the High Wind Warning. Highest winds in these areas still expected to be along the Big Sur Coast, Santa Lucia Range, San Benito County, and towards the northern end of the Salinas Valley including the central Monterey Bay coastline. Another noteworthy bit to add...our criteria for bomb cyclogenesis at this latitude is about 17 millibars in 24 hours. Current model guidance does suggest this will happen during a short period Tuesday morning, though impacts remain the same regardless of if we technically meet this criteria or not. && .PREV DISCUSSION...as of 03:11 PM PDT Monday...A break in the rain for the rest of today as winds remain light and mainly clear, with highs in the lower elevations in the mid 50s to low 60s, and into the mid 40s to low 50s for the higher elevations. A storm system is approaching California and will impact the SF Bay Area and Central Coast starting early on Tuesday. While the system is associated with an atmospheric river approaching the state, the main moisture tap will be directed to our south in southern California and Baja California. For our area, winds will be the main issue, with the most impactful gusts Tuesday morning into the afternoon. A High Wind Warning is in effect from 7 AM to 9 PM Tuesday in the mountains of Monterey and San Benito Counties, where southerly gusts of over 70 mph are expected. Elsewhere, a Wind Advisory is in effect for the East and South Bay, the San Mateo Peninsula, and the lower elevations of the Central Coast, also from 7 AM to 9 PM Tuesday, with southerly wind gusts of up to 40-50 mph are expected, with more intense gusts in the higher elevations. The North Bay should see gusts of up to 20-25 mph. Much of the uncertainty in the strength of the wind gusts is in the wider SF Bay region, as models are still having difficulty on the location of a surface low that`s expected to enhance wind gusts. The global GFS and European models are bringing the low to a stall off the coast of the San Mateo Peninsula, while the higher resolution HRRR and NAM are bringing the low onshore along the Central Coast. We will continue to closely monitor the surface low and its evolution as the impact comes closer. Rainfall will be a secondary impact in our area, although expected totals are not as high as those in southern California. here too, the most intense rain is expected Tuesday morning and afternoon. The lower elevations of the North Bay, SF Bay Area, and Central Coast are currently forecast to see three-quarters of an inch to one inch of rain, save for the most northern parts of Sonoma County where rain totals go down to half an inch. The Central Coast mountains remain the regional epicenter of rain impacts, with rain totals in the Santa Lucia mountains expected to range from 2 to 3 inches, and the Santa Cruz and interior Monterey and San Benito mountains expected to reach 1.5 to 2.5 inches of rain. Higher elevations in the Bay Area should expect 1 to 2 inches of rain. A slight chance of thunderstorms exists into the post-frontal environment on Tuesday evening, especially on the Central Coast. The combination of continued rain, high winds, and saturated soils poses a set of hazards that, at this point, are now familiar to many in our region. The rain brings a chance for minor urban and small stream flooding, and with soils already so saturated from the storms earlier this month, the risk of shallow landslides continue. High wind gusts will also result in downed trees and power lines, possibly resulting in isolated power outages, and difficult driving for high profile vehicles. If your area is prone to power outages, use today to prepare, and remember to "turn around, don`t drown" when encountering a flooded roadway or path. The heaviest rain diminishes Tuesday evening, with post frontal showers expected through Wednesday. Current predictions leave Thursday to Saturday relatively dry with very little, if any, rain. Any rain that falls in the next three days is not expected to rise past half an inch in total. All attention then focuses on the beginning of the next week, where early model indications suggest another system coming through, the exact details of which won`t become clear until later in the week. In addition, low temperatures next weekend are expected to dip into unseasonably cold readings, with lows in the low to mid 30s expected Saturday and Sunday morning in the interior valleys, including the Sonoma, Napa, and Salinas Valleys, and into the higher elevations. With the occurrence of "bud break" in the North Bay vineyards, and the Spring harvest approaching, this is a particularly sensitive time for the agricultural industries. More details on the low temperatures and the system next week will come as the forecast gets refined later in the week. && .AVIATION...as of 10:50 PM PDT Monday..For the 00z TAFs..VFR lasts into early Tuesday morning. Easterly and southeasterly winds begin to increase as a strong surface low approaches. This low pressure system will bring moderate to heavy rain starting early morning lasting through the afternoon with scattered showers continuing through the evening and lingering into the night. Expect MVFR CIGs for most of the TAF period. As the center of the low moves inland, southerly winds will increase. Strong gusts of 35 to 40 knots possible across the region, primarily south of the Golden Gate. Winds begin to diminish int Tuesday night. Vicinity of KSFO...VFR last until early Tuesday morning before rain arrives at the terminal around 12Z with MVFR conditions expected. Winds will turn easterly around that time and increase as low approaches. Winds shift southeast as low moves inland and eventually become even more southerly into the afternoon. Wind gusts become strongest between 20z and 04z with gusts up to 34 knots (but potentially higher depending where low sets up and will continue to monitor). Expect winds to reduce into Tuesday night, but they will stay breezy. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...VFR lasts into the morning before MVFR through the rest of the TAF period. Southeast winds increase starting in the early morning and look to continue to gain strength through the morning with 40 kt gusts possible. Moderate, to at times of heavy, rain will accompany the increased winds. Rain chances as well as the elevated winds begin to reduce into Tuesday night. && .MARINE...as of 10:47 PM PDT Monday...A robust low pressure system arrives overnight tonight, moving through the coastal waters through the morning Tuesday, bringing gale force gusts to much of the waters south of Pigeon Point. Storm force gusts possible as low moves through Tuesday morning. Widespread rain also expected overnight through Wednesday. By midweek, a west swell will combined with wind wave will create high and steep seas. A long period northwesterly swell also expected to arrive towards the end of the week. && .MTR WATCHES/WARNINGS/ADVISORIES... .Tngt...SCA...SF Bay from 3 AM SCA...Pt Arena to Pt Reyes 0-10 nm from 3 AM SCA...Pt Reyes to Pigeon Pt 0-10 nm from 3 AM GLW...Mry Bay from 3 AM GLW...Pigeon Pt to Pt Pinos 0-10 nm from 3 AM GLW...Pt Pinos to Pt Piedras Blancas 0-10 nm from 3 AM GLW...Pigeon Pt to Pt Piedras Blancas 10-60 nm from 3 AM SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm until 3 AM SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm until 3 AM SCA...Pt Arena to Pigeon Pt 10-60 nm from 3 AM && $$ PUBLIC FORECAST: DialH/Behringer AVIATION: Murdock MARINE: McCorkle 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 210426 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 926 PM PDT Mon Mar 20 2023 .SYNOPSIS... Periods of rain and mountain snow will occur tonight across the Cascades, Columbia Basin, southeast Washington and the central and southern Idaho Panhandle. Precipitation chances decrease Tuesday. Wednesday is expected to be a dry day. Cool, breezy and showery weather will return Thursday and persist into the weekend. && .DISCUSSION... Update for Tonight: Southwest winds at Spokane International airport and northeast winds from Coeur d`Alene northward outline the battle between drier winds from the north and more moist southwest flow into the Palouse and central Basin. 24 hour totals of rain are less than a tenth of an inch of precipitation at Pullman, WA and Moses Lake. There was only a trace of rain in Wenatchee, Spokane and Lewiston. The moist boundary will continue to sag south and east overnight. As clouds clear aloft we`ll need to watch out for areas of fog development later tonight into tomorrow morning from south of Spokane into Pullman and along the Highway 395 corridor. The overall trend will be an increase in northeast wind up to 10 mph Tuesday moving the clouds and drying the airmass. By mid-afternoon Tuesday much of the low cloud cover will be gone over the Inland Northwest. TC Rest of Tonight through Wednesday: The potential for precipitation continues tonight, with drier conditions developing for Tuesday and Wednesday. The Inland Northwest is in a somewhat messy pattern this afternoon. On the large-scale the region is under a broader trough. A deformation axis stretches across WA state (from northwest to southeast) and trails into southwest MT. A shortwave disturbance will continue to track south of that feature tonight, while a backdoor front moves in from the north. Precipitation chances will remain high tonight near the Cascade crest, into the Columbia Basin, Palouse and southern Panhandle. Other chances will be found over the Spokane/CdA area into the central Panhandle, with chance trailing off north of here. The higher precipitation amounts are expected around the Upper Columbia Basin east- southeast toward the Palouse and Camas Prairie (i.e. where the potential for >0.10" is highest), while lighter amounts are expected elsewhere. As the night progress and the southern shortwave shifts out and the northern boundary sags south, precipitation chances will decline from the north. By Tuesday morning the primary precipitation chances will be near the Cascades, portions of the deeper Columbia Basin and especially southeast WA and the lower Panhandle; then chances continues wane into the afternoon. Clouds decline into Tuesday and Wednesday. Snow levels will be around 3.5-4.5kft this afternoon, then they gradually fall from the northeast through the night so that by Tuesday morning snow levels are around 1-2.5kft over north ID and far NE WA, to 3-3.5kft over the remainder of the CWA. They recover to around 3-4kt Tuesday afternoon. The primary accumulating snow potential will be near the Cascades crest, Central Panhandle mountains, the Blue and the Camas Prairie. Most of these locations are expected to see 1" or less. However the Blue Mountains and Camas Prairie could see 1-3 inches, with isolated amounts near 5 inches in the higher terrain south of Waha. Aside from precipitation, tonight/early Tuesday there is the potential for some fog over the sheltered mountain valleys, across the higher Palouse and possible developing around the West Plains of Spokane. However this largely expected to be patchy if it develops. Temperatures fall into the mid to upper 30s tonight, with some 20s around the mountains and northeast WA and north ID. They rebound to the upper 40s and lower to mid-50s Tuesday, then drop toward upper 20s and lower 30s going into Wednesday morning. Wednesday look mild with temperatures in the 50s, and a few low 60s toward the deeper Columbia basin. /Solveig Wednesday night through Monday: Eastern Washington and North Idaho remain influenced by the cold conditionally unstable airmass in a broad trof over the area with the jest stream well down to the south. There is potential for minor disturbances rotating around the outer edges of another trof dropping down from the northwest to spark off generally convective valley rain showers and mountain snow showers. Thursday night into Friday ensembles suggests this earlier mentioned trof dropping down from the northwest passes through as a negatively tilted cold front through the generally conditionally unstable airmass over the area. The cold unstable airmass looks to support typical snow/graupel showers down to valley floors most of the time Thursday night into Friday. This will allow for increased gusty southwest winds Thursday and Thursday night. NBM 4.1 suggests a near 40 percent probability of wind gusts equaling or exceeding 30 mph Thursday evening. This could complicate burning of fine pre-greenup dead fuels, especially in the Columbia Basin where a rain shadow of sorts may develop. As such some of our social media and weather story messaging addresses it. A weak positively tilted shortwave ridge may slide down in the northwest flow on the west edge of the large broad trof influencing North America over the weekend which results in a weekend forecast favoring very light QPF associated with potential for light mountain snow showers with spotty hit and miss light rain and snow showers along the outer edges of a rain shadow of varying width between the lee of the Cascade Crest and North Idaho. Cluster analysis show both timing and intensity differences for day 7 (Monday) with positioning of another area of low pressure dropping down from the northwest. Cluster 1 with 36 percent of the ensemble members (containing 64% of the EPS members) is suggesting more of a split flow (and possibly drier) solution while Cluster 2 with 28 percent of the ensemble members suggest greater potential for moisture running up along outer eastern edge of a more closed off low nested in a trof further west and off the coast. This moisture feed and disturbances associated with it may allow for a possibly cloudier and wetter Monday. Temperatures will fall after Wednesday`s peak for the seven day forecast and bottom out Friday with the coldest (and conditionally unstable) airmass overhead favoring the coldest daytime high Friday up with the coldest overnight lows Friday night/Saturday Morning followed up thereafter with a very slow and gradual warming trend. As far as significant mountain pass snow accumulation goes the NBM 4.1 is giving a 57 percent of exceeding 6 inches of snowfall over the 24 hour period ending 5 PM PDT Friday for Stevens Pass. For Lookout Pass for the same period the probability is only 32 percent. /Pelatti && .AVIATION... 06Z TAFS: A front dropping in from the north early Tuesday will bring areas of rain over the Cascades to the Palouse and lower Panhandle, with the best chances around PUW/LWS and secondarily EAT/MWH and smaller chance near GEG/SFF/COE. The potential will continue through the night and diminish Tuesday. The best potential for MVFR/lcl IFR conditions will be near PUW/LWS with HREF indicating near 60-90% at PUW and 50-60% at LWS. For other TAF sites, the HREF shows the best chance of MVFR developing overnight/early Tuesday before improving at 18-20Z Tuesday. / && .PRELIMINARY POINT TEMPS/POPS... Spokane 35 53 29 56 32 51 / 40 10 0 0 0 40 Coeur d`Alene 31 51 27 53 30 48 / 20 0 0 0 10 40 Pullman 37 50 31 52 32 49 / 70 40 0 0 10 40 Lewiston 41 56 34 57 36 56 / 60 40 0 0 10 20 Colville 27 53 26 56 28 50 / 10 0 0 0 0 40 Sandpoint 30 48 28 51 29 44 / 10 0 0 0 10 60 Kellogg 32 48 27 51 30 44 / 30 10 0 0 10 70 Moses Lake 36 57 32 60 33 57 / 60 10 0 0 0 10 Wenatchee 37 52 33 55 34 52 / 60 30 0 0 0 10 Omak 34 53 31 54 32 51 / 20 0 0 0 0 20 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...None. && $$

000 FXUS66 KPDT 210352 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 852 PM PDT Mon Mar 20 2023 .EVENING UPDATE...A weak upper-level wave splitting off from its parent low centered over the Pacific will depart to the east overnight, leaving a band of light showers across the Basin spreading into the eastern mountains. Radar returns have persistently shown precip in the aforementioned areas through the evening, however returns are on the weaker end and recorded amounts have been light - less than a few hundreths across the Basin. The NW mid-level flow may support some upslope shower activity along the foothills of the Blues, but the overall expectation is that dynamic forcing will be too limited to support any kind of shower activity that isn`t light in intensity. For the Blues, could see a couple of tenths through Tuesday morning, however snow levels are above 4000 ft across most of the range as of around 9 PM local time, so snowfall impacts should be limited to the crests. I-84 should largely be spared of any meaningful snowfall accumulation, outside of perhaps the early morning hours when snow levels will be at their lowest, but even then, not anticipiating more than an inch or two for the mountain pass. Made minor adjustments across the board to the forecast package, focusing mainly on precip coverage/PoPs to capture the current band of precip on radar, as well as the potential for overnight upslope precip. No changes to the overall messaging behind the latest forecast, however. Evans/74 .AVIATION...06z TAFs...Variable conditions are possible through the overnight, before VFR conditions are expected to prevail by daybreak Tuesday. Light rain is possible primarily for PDT and ALW, however precip is limited such that the main impact will come in the form of lower cigs, which have already reached sub-IFR this evening for ALW. Low-level moisture may make for low cigs below 5 kft until morning for sites outside of BDN/RDM, before drier air prevails and all sites are expected to clear out and reach widespread VFR conditions. Breezy winds may persist in DLS through the first few hours of the period, before decreasing as winds shift more north and east across all sites Tuesday, with speeds less than 15 kts. Evans/74 && PREV DISCUSSION... /issued 246 PM PDT Mon Mar 20 2023/ SHORT TERM...Today through Wednesday...HAPPY SPRING EQUINOX!!! Current radar is showing some scattered showers still lingering through the Ochoco-John Day Highlands and across the northeast corner of the forecast area. Ground observations are showing those areas having received 0.02 to 0.05 inches of precipitation in the last 3 hours. Satellite imagery is continuing to show the region to be mostly cloudy with thick stratus clouds across the entire area, with high clouds beginning to make their way across as well. Models show that the tongue of low pressure that was over the area has begun to recede to the west, but precipitation is expected to continue to linger across most of the region with a bit of drying across Central OR. Winds have increased through the Gorge, Basin and foothills with sustained winds between 15 to 20 mph and gusts to 30 mph have been recorded, but they will decrease through the evening. Highs today so far have been mild with temperatures reaching the mid 40s to low 50s across the region with higher elevations in the 30s. Overnight all models show the region will begin to dry out. The EFI index is showing below average temperatures. However until then, the ensembles and NBM show snow totals (confidence 50-80%) tonight through tomorrow morning are 0.5-2 inches along the Cascades, 2-5 inches along the Blue Mountains with higher amounts at the peaks, and 1-3 inches along the Ochoco-John Day Highlands. Rainfall elsewhere will be between 0.01 with the exception of La Grande seeing up to a quarter of an inch (50-60%). EFI, NBM and ensembles are showing overnight temperatures to be near normal seasonal average with low to mid 30s through the Gorge, foothills of the Blues, the Basin and adjacent valleys. Central OR and the higher elevations will see lows in the 20s to low 30s. There will be some locally cooler areas that could see lows in the mid teens. Tuesday the models show that the region will be under a split flow pattern between the cut off low to the south of the region and the next low pressure system sitting in the Gulf of Alaska. Models do seem to be in slight disagreement on whether or not there will be continued precipitation associated with the split flow. GFS is the most bullish of the models putting a precipitation band along the northern portion and the mountains of the region whereas the remaining models only show light precipitation over the Blues and Wallowa County. NBM and ensembles show that there will be up to 1 inch of snow excepted across the region with slightly higher amounts in the OR Cascades overnight into Wednesday. NBM and ensembles have temperatures continuing on the mild side, with the EFI showing a continued near normal trend with the high temperatures, but below average for the lows. Highs will be in the 50s through much of the region with the higher elevations in the low to mid 40s. Lows will dip to the mid 30s through the majority of the region and elsewhere at or near freezing. Wednesday models show the split flow continuing over the region as the cutoff low continues to push onshore in California and a high pressure system begins to sink southward from British Columbia. Models show dry conditions over the area beginning late morning with a west to southwest flow. Winds will have gradually decreased and temperatures will have bounced a few degrees warmer with highs in the low 60s through the Basin and and the Gorge, 50s in the foothills of the Blues, Central Or, Kittitas and Yakima Valleys, and 40s in the higher terrains. Bennese/90 LONG TERM...THURSDAY THROUGH MONDAY... The extended period is characterized by an initial negatively tilted trough early in the period, followed by a transient ridge before a stronger system slides down the Pacific Northwest coast over the weekend and into the early part of the workweek. This will provide significant mountain snowfall Thursday into Friday, as well as breezy to windy conditions during the same timeframe. The weekend system will also provide reinforcing mountain snow chances (60-70%), with a slight chance (10-20%) of lower elevation rainfall late Sunday afternoon/evening. The main concern through the latter half of the week and into the weekend resides with the potential (60-70%) for snowfall over the Cascades, Northern Blue Mountains, and Wallowas to reach advisory criteria above 4000 feet, incurring snow amounts of 3 to 10 inches Thursday through Friday, with up to 14 inches possible for higher elevations. Elevated winds will be the secondary concern Thursday afternoon, as gusts of up to 50 mph out of the west will be possible across the Simcoe Highlands, with potentially 30-40 mph gusts through Central Oregon, Eastern Gorge, and the Blue Mountains/Foothills. An upper level, negatively tilted trough will be approaching the Washington/Oregon coasts on Thursday, pushing onshore through the afternoon and continuing to drive into the Great Basin into Friday morning. Snow levels will initially be between 2000 and 3000 feet Thursday morning before plummeting into the 500 to 1500 foot range on Friday. This is associated with a cooler air mass behind the trough, which will also allow for below average temperatures to return to the area as highs hover in the upper 40s to low 50s for lower elevations of the Basin. Snow chances will be increasing through the morning hours along the Cascades before extending into the Blue and Wallowa Mountains through the afternoon and much of the day on Friday. NBMv4.1 highlights a 60-70% chance of 8 inches over Snoqualmie pass, and an 80-90% chance of 8 inches or more over the Oregon Cascades, and a 20-30% chance of 8 inches or more over the Northern Blue Mountains over a 24 hour period from Thursday night to Friday night. Dropping the amounts to 4 inches or more pushes the Northern Blues up to a 70-80% chance, which allows for moderate confidence (50-70%) in the aforementioned snow totals of 3-10 inches over our mountain zones. Lower elevation rain chances will peak through the late afternoon and evening on Thursday and again on Friday as northwest flow aloft will keep moisture streaming into the region in the wake of the exiting system on Friday. However, the main impacts will be felt at elevation along our mountain zones, with little to no rain accumulations expected for the Yakima/Kittitas Valleys and the Lower Columbia Basin. A light dusting of snow will be possible along the foothills of the Blues and through Central Oregon, but any chance of snow actually sticking will be minimal as the precipitation will begin as rain with much less moisture anticipated behind the cold front associated with the passing shortwave. Isobars will be tightening as the system approaches and drives through our area, with pressure gradients from PDX to PDT reaching between 4 to 7 mb. This will be enough to allow for gusts of up to 50 mph over the Simcoe Highlands with 30-40 mph gusts possible over Central Oregon, Eastern Gorge, and the foothills of the Blue Mountains. The NBMv4.1 shows a 80-90% chance of gusts reaching 55 mph through the Simcoe Highlands Thursday, with a 70-80% chance of wind gusts reaching 48 mph over the Blue Mountain foothills and along the east slopes of the Oregon Cascades. Thus, confidence in these wind gust values are also moderate (50-70%), which may warrant wind highlights for the aforementioned areas along with winter highlights over the Cascades and Blue Mountains. A weak upper level ridge will infiltrate into the area from the west into Saturday, allowing for drier and warmer conditions to ensue through the weekend. However, northwest flow aloft should continue to keep the chance for light mountain snowfall of only 1-2 inches daily through the weekend. An upper level low pressure will be dropping along the British Columbia coast Sunday before arriving offshore of the Oregon Coast into Monday morning, which will keep mountain snow chances (30-40%) in the forecast with a slight chance (15-20%) of lower elevation rainfall late Sunday into Monday. Guidance is in good agreement with the overall weather pattern, but discrepancies arise relating to shortwave strength and the resulting dropping system over the latter half of the weekend. The ECMWF incurs a slightly stronger and delayed shortwave than the GFS, which relates to a slightly drier and less windy scenario versus the GFS. The ECMWF then quickly digs a system to our south to allow for upper level ridging to take hold early Saturday versus a much weaker shortwave and resulting ridge into the early part of the weekend. This results in the closed low pressure that rides down the British COlumbia/Washington/Oregon coasts being more offshore with the GFS scenario versus the ECMWF, which provides a wetter result Sunday into Monday with the GFS. These discrepancies are visualized via the 500 mb EOF Patterns, as the cluster phase space sheds little light on either scenario. This is represented by a larger ensemble spread with the ECMWF, but a more representative ensemble mean with the GEFS. Thus, the NBM was utilized in order to provide an applicably weighted scenario through the extended period. 75 && .PRELIMINARY POINT TEMPS/POPS... PDT 38 53 32 54 / 70 10 0 0 ALW 42 56 32 55 / 80 20 10 0 PSC 41 58 34 60 / 60 10 0 0 YKM 40 56 31 60 / 50 20 10 10 HRI 39 58 32 60 / 60 10 0 0 ELN 38 53 31 58 / 40 20 10 10 RDM 25 51 30 52 / 0 0 10 20 LGD 33 48 29 49 / 60 20 10 10 GCD 30 48 27 47 / 30 20 10 20 DLS 36 59 38 63 / 10 10 10 10 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && $$ SHORT TERM...74 LONG TERM....75 AVIATION...74

000 FXUS65 KREV 202140 AFDREV Area Forecast Discussion National Weather Service Reno NV 240 PM PDT Mon Mar 20 2023 .SYNOPSIS... A quick break is expected today, outside of a line of scattered showers from Lassen to northern Pershing Counties, as well as some isolated showers over Mono County this afternoon. Our next storm arrives early tomorrow morning, bringing heavy mountain snow and valley showers through Wednesday morning. Heaviest snowfall will impact Mono County mountain communities, with concerns for additional snow loading. && .SHORT TERM... Happy first day of astronomical spring! It will actually feel like spring today, as generally dry and mild conditions prevail. Breezy southwesterly winds will taper off through the evening as a weak shortwave exits the region. Isolated snow showers will develop this afternoon over the Sierra crest in Mono County courtesy of weak instability from daytime heating, with some spillover into the Eastern Sierra possible. Those spring conditions won`t last very long as yet another winter storm arrives early Tuesday morning. A strong upper-level low is expected to track inland into central California early tomorrow morning. High-resolution guidance now suggests this low will split and develop two distinct areas of precipitation, with one rotating northeast into northern Nevada and the other rotating southeast along the Sierra. * Eastern Sierra: Heavy snow will initiate first over the high Sierra in Mono County early Tuesday morning ahead of the splitting low, with a period of 1-2" per hour snowfall rates likely (80% chance) through late morning. Snow will become more convective in the late afternoon as the low splits and lifts a precipitation band northward. The other low will continue rotating south along the California coast and provide forcing for scattered heavy snow showers and isolated thunder (15% chance) into the evening. Shower intensity will taper overnight into early Wednesday morning as the low continues tracking southward. There is high confidence for heaviest snow to impact Mono County, and snow levels will support accumulation down to all valley floors. Expect up to 2-3 feet along the crest, 8-15 inches for communities along US-395 south of Conway Summit, and 2-8 inches for communities along US-395 from Bridgeport Valley northward. * Elsewhere: High-resolution guidance indicates the precip band associated with the splitting low will reach the Tahoe Basin and Greater Reno-Carson-Minden areas by late morning, then Lassen County and the remainder of western Nevada by early afternoon. The band will continue rotating north out of our region by Tuesday evening, before it reverses and begins moving southeast on Wednesday morning. Additional light snow showers are possible as the band digs back through the region, mainly impacting the west- central Basin and Range. Snowfall totals decrease substantially into the Lake Tahoe region with 2-6 inches of new snowfall expected for the Tahoe Basin, except 6-12 inches above 7000 feet. Snow totals drop off even further into northeast California, with 1-4 inches likely. Most precipitation is expected to fall as snow in western Nevada, but accumulations will likely be minimal as the ground is much warmer due to the higher sun angle. -Whitlam .LONG TERM... For late this week, overall troughiness will stick around across the West, resulting in multiple waves or storms to drop through the base of the trough bringing more active weather, including showers and winds to the Sierra and western Nevada. For Thursday into Friday, a quick moving shortwave will move across northern CA and bring renewed snow showers to areas along and north of Interstate 80. By Friday into Saturday, some lingering showers may still be around considering the trough is still across the West. Also, with the higher sun angles paired with the moisture we are looking at the potential for some afternoon/evening showers to develop even in the absence of an actual storm or shortwave. Generally, plan on mid to high level cloudiness, near to below normal temperatures, as well as potential for rain/snow showers across the region as the weather pattern remains active from late week into the weekend. A more potent storm is in the queue for Tuesday next week with signs of more precipitation and winds for the Sierra and western Nevada. Even though simulations vary on the track and timing of this storm, any additional precipitation to the region will hamper ongoing recovery efforts and exacerbate impacts to mountain communities. -Edan && .AVIATION... Skies have cleared nicely in the last several hours per latest satellite observations, with some passing mid- to high-level clouds remaining early this afternoon. Prevailing VFR conditions will persist well through the afternoon and into the evening hours in between storms. On another note, westerly surface winds are rather breezy for most areas, especially across Sierra Front terminals (RNO-CXP-MEV) where gusts up to 20 kts are being reported as of 2 PM. Gusty west winds will continue through around 03Z before becoming generally light and variable overnight. Flight conditions will begin to deteriorate early Tuesday morning as a band of rain & snow showers lifts northward across the region. As such, showers will arrive to MMH-024(Lee Vining) around 12Z and TRK-TVL-RNO-CXP-MEV terminals between 15Z-18Z. Mountain obscuration and periods of MVFR/IFR conditions are likely for all terminals on Tuesday, especially in the Sierra (KMMH in particular) where heavy snow is possible. Remnant, spotty showers will occasionally reduce CIGS/VIS late Tuesday afternoon through Wednesday morning in the wake of the primary band of rain and snow. East to southeast surface winds will increase to a sustained 10-15 kts with occasional gusts to 20-25 kts Tuesday morning. Meanwhile, E-SE FL100 winds will strengthen to 30-40 kts across the Sierra and W.NV, yielding the potential for mountain wave turbulence from Sierra crest westward into California between 15Z-21Z. As a surface low tracks northward through W. NV, winds will gradually shift from the south/southwest sometime during the afternoon before becoming generally light and variable Tuesday night. Beyond Tuesday, a few lingering showers will periodically reduce CIGS/VIS for Sierra terminals into the weekend. The next chance for a strong, organized storm appears to be early next week. -Salas && .AVALANCHE... Southwest ridge wind gusts will remain breezy through the evening with gusts 40-60 mph. Wind direction transitions Tuesday morning with east ridge wind gusts 30-50 mph for the Tahoe Basin and southerly ridge wind gusts 25-50 mph for the Eastern Sierra. Freezing level could rise to around 7000` today in the Tahoe basin around 8000` in Mono County. The next moderate storm moves into the region Tuesday morning with the heaviest precipitation forecast for the eastern Sierra where another 1-2" of QPF is possible Tuesday. Lesser amounts of 0.5-0.75" are projected for the central Sierra with the primary jet directed towards southern California. Snow levels are expected near all valley floors as the cold core of the storm migrates over the Sierra. Snow ratios will be in the 13-16:1 range for Tuesday- Wednesday. Thunderstorm potential ramps up for Tuesday afternoon with a 15% chance of lightning for the eastern Sierra. -Zach/Edan && .REV Watches/Warnings/Advisories... NV...Winter Weather Advisory from 5 AM to 11 PM PDT Tuesday NVZ002. Lake Wind Advisory until 7 PM PDT this evening for Pyramid Lake in NVZ004. CA...Winter Weather Advisory from 5 AM to 11 PM PDT Tuesday CAZ072. Winter Storm Warning from 5 AM Tuesday to 5 AM PDT Wednesday CAZ073. && $$

000 FXUS66 KSTO 202238 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 338 PM PDT Mon Mar 20 2023 .SYNOPSIS... Showers return late tonight and continue through Wednesday, heaviest Tuesday, with afternoon thunderstorms possible. Accumulating snowfall is expected above 4000 feet. There will be some gusty southerly winds on Tuesday. The cool and unsettled weather pattern will continue through mid to late week, with periods of showers. The weekend will see some cold morning temperatures. && .Discussion... Short-wave ridging has brought a break in precipitation to the region today and tonight. There were some lingering showers earlier this morning, mainly over the Sierra and the northeast foothills. This afternoon there are just some scattered clouds clouds left over the area. The Winter Storm Warning was allowed to expire at 11 am PDT. The next storm system arrives late tonight and continues into Wednesday. This will be a cold closed low pressure system from the Gulf of Alaska which will move southward along the California coast and then move inland over Southern California. The trajectory of this system will bring the greatest moisture into central and Southern California. This system will bring lower snow levels than in recent storms, around 3000-5000 feet. The heaviest amounts for northern interior California will be in the Sierra south of US Highway 50, where 1 to 2 feet of snow is possible above 6000 feet. A Winter Weather Advisory is in effect 5 am PDT Tuesday to 5 am PDT Wednesday, with delays in travel likely at times. Gusts to 50 mph are possible and along with the snow could bring some reduction in visibility at times. Some breezy southeasterly winds are possible Tuesday, gusting up to 25-35 mph over the northern San Joaquin Valley, lighter to the north. Highest forecast rainfall amounts through Wednesday are 0.75"-1.00" for the Delta and locations in the Valley from Sacramento southward. Isolated thunderstorms are possible Tuesday afternoon and evening for the northern San Joaquin and southern Sacramento Valleys. Instability is not especially strong but there is a fair amount of shear. Small hail and heavy rain are the main threats with any thunderstorms that form. Some residual showers will linger into Thursday on the backside of the system, especially over the mountains. A weak system brushing by to the north could bring more light mountain showers on Friday. EK && .EXTENDED DISCUSSION (Friday THROUGH Monday)... Ensembles show longwave troughing continues off the West Coast through the extended forecast period with series of shortwaves moving through. This will keep unsettled weather Friday through Monday with showers and foothill/mountain snow showers. Below normal high temperatures expected, with some cold morning lows. The NBM projects Valley lows in the mid to low 30s, potentially around freezing for the northern Sacramento Valley Sunday morning. Clusters show good agreement in a stronger low early next week, but timing and location differences are bringing uncertainty, so it remains unclear how impactful this system will be. Stay tuned! EK && .AVIATION... In Central Vly, mainly VFR except lcl MVFR/IFR possible til about 18z. Sfc wind generally at or below 12 kts next 24 hrs. Foothills/mtns areas MVFR/IFR with lcl LIFR possible. Areas of SW-W sfc wind gusts up to 30 kts. && .STO WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from 4 AM Tuesday to 4 AM PST Wednesday for West Slope Northern Sierra Nevada-Western Plumas County/Lassen Park. && $$

000 FXUS65 KMSO 202043 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 243 PM MDT Mon Mar 20 2023 ...SNOW RATES EXCEEDING 1 INCH PER HOUR THIS EVENING ACROSS SOUTHERN IDAHO COUNTY, WESTERN LEMHI COUNTY, AND SOUTHWEST MONTANA... .DISCUSSION... A low pressure circulation moving from north central Idaho to southwest Montana through Tuesday morning will produce impressive snowfall rates for portions of the Northern Rockies. The principle area of concern continues to be north central Idaho and southwest Montana, where the most recent high resolution models suggest a 60 percent probability of snowfall rates exceeding 1 inch per hour at times 6pm MDT/5pm PDT - midnight MDT/11pm PDT for elevations 4000 feet and higher. As such, mountain passes, high-elevation valleys, and backcountry corridors will see the brunt of the impact, with reduced visibility and snow covered roads contributing to hazardous winter driving conditions. In fact, in and around Cobalt and Williams Creek area of western Lemhi County, snow accumulations up to 12 inches will severely impede travel this evening and overnight. Also, population centers of southwest Montana (such as Georgetown-Anaconda-Butte) will develop hazardous winter driving conditions with the snow sticking by sunset and continuing through early Tuesday morning. Wednesday-Thursday, a closed low pressure circulation is projected to move east across the northern Great Basin, with light mountain snow and valley snow-rain mix clipping the southernmost extent of north central Idaho and southwest Montana. Snow accumulation depicted by models and ensembles suggest that hazard winter travel impacts will be confined to Lemhi County south of Salmon (along Highway 28). Even so, high-end snow estimates barely reach 3 inches accumulation for pass elevations, such as Gilmore Summit. Nearly 100 percent of models and ensembles now depict a vigorous cold front across the Northern Rockies on Friday, with gusty winds and some intense snow showers developing after the front passes. The cold air aloft in-place throughout the upcoming weekend will be a catalyst for fast-developing snow and graupel showers each afternoon. Watch for rapidly changing road conditions and visibility, particularly over area mountain passes. There seems be little break between storm systems for the Northern Rockies, with yet another low pressure circulation moving along coastal Pacific Northwest early next week. Roughly 40 percent of models and their ensembles suggest some kind of precipitation event, however even the accumulations depicted are quite light. && .AVIATION... Terrain obscurations will be common for Northern Rockies air space south of KMSO through 22/0000Z. Snow showers will reduce visibility, particularly over 4000 feet MSL, during this time. 1 inch per hour snow rates will reduce visibility below 1/4 mile for air space around KGIC-KSMN-KBTM 21/0000Z-22/0900Z. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...Winter Weather Advisory until noon MDT Tuesday for Bitterroot/Sapphire Mountains. Winter Weather Advisory until noon MDT Tuesday for Butte/Blackfoot Region. ID...Winter Weather Advisory until 11 AM PDT Tuesday for Southern Clearwater Mountains. Winter Weather Advisory from 7 PM this evening to 5 AM PDT Tuesday for Lower Hells Canyon/Salmon River Region. Winter Storm Warning from 6 PM this evening to 6 AM MDT Tuesday for Western Lemhi County. Winter Weather Advisory until noon MDT Tuesday for Eastern Lemhi County. && $$

000 FXUS65 KBOI 210323 AFDBOI Area Forecast Discussion National Weather Service Boise ID 923 PM MDT Mon Mar 20 2023 .DISCUSSION...Evening water vapor satellite imagery showing a well defined upper low over s-central Idaho this evening. A shield on the backside of the low that extends from SE Oregon into central Idaho will gradually shift eastward tonight as the low moves into eastern Idaho. Mountains will continue to see accumulating snow with rain, a rain/snow mix or straight snow in the valleys depending on elevation. Sites below 3kft feet expected to stay rain, with a rain/snow mix above 3kft and snow above 3500-4000 ft. The precipitation shield will weaken as it moves eastward overnight, resulting in lesser amounts over s-central Idaho. Have updated the forecast for precipitation chances and amounts through tonight. In the Snake Plain any light snow accumulation will be limited to areas east of Boise. && .AVIATION...Areas MVFR in valleys with widespread IFR in the mountains obscuring terrain tonight. Improving conditions in SE Oregon after 21/06Z and after 21/12Z in SW Idaho. Rain and snow with snow levels 3-4kft through Tuesday morning. Areas IFR in fog or low stratus through 18Z Tuesday, otherwise VFR. Surface winds: W-NW 5-15 kt becoming easterly 10-20 kt after 21/21Z. Winds aloft at 10k feet MSL: W-NW 10-25 kt becoming east 10-20 kt after 21/21Z. && .PREV DISCUSSION... SHORT TERM...Tonight through Wednesday night...An upper trough will continue to move through the region tonight for more valley rain/snow and mountain snow showers. The colder air aloft associated with the center of the system will lead to isolated thunderstorms in south-central Idaho this afternoon. There have already been a couple of lightning strikes detected in southern Owyhee County earlier this afternoon. The shower activity will shift into southwest Idaho tonight. An additional 1 to 4 inches are expected in the mountain valleys of central Idaho, with up to 6 inches in the mountains. A Winter Weather Advisory remains in effect for the West Central Mountains tonight. Winds are expected to be light in the mountains, so blowing/drifting snow is not a concern. The shower coverage will decrease on Tuesday, but there is still a 20-30 percent chance of snow showers in central Idaho. Another Pacific storm system will move into the Great Basin Tuesday night through Wednesday. The storm track will determine the northern extent of the showers. The latest models have trended further north with the showers, and could reach the Boise area based on some of the models. Snow levels will be lower with this system than the current one, generally in the 3000-4000 foot range for a mix of rain and snow in the valleys. Snowfall totals of 2 to 5 inches are expected in the higher elevations along the Nevada border and in central Idaho east of Boise, along with up to 2 inches in the valleys above 3500 feet (including the Western Magic Valley). Winds will be breezy to locally windy at times. Temperatures will remain about 5 to 10 degrees below normal. LONG TERM...Thursday through Monday...Cool and unsettled conditions will continue throughout the extended period as a series of storm systems pass across the Pacific Northwest. A series of shortwave troughs will generate shower activity nearly every day with a potential break on Sunday ahead of a deep Pacific trough. Snow levels near 4000 ft MSL on Thursday will lower to valley floors by Friday morning, which poses the threat of light snow across the Snake River Plain during the Friday morning commute. Snow levels will stay at valley floors through Sunday before a warm front lifts across the region on Monday. Snow accumulations across the lower valleys will be minimal through the extended period, while mountain valleys will see 2 to 6 inches of snow accumulation and up to an additional foot of snow over the higher peaks. Temperatures through Sunday will remain 5 to 10 degrees below normal before several degrees of warming on Monday. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...Winter Weather Advisory until 6 AM MDT Tuesday IDZ011. OR...None. && $$ www.weather.gov/Boise www.facebook.com/NWSBoise www.twitter.com/NWSBoise DISCUSSION...DG AVIATION.....DG PREV SHORT TERM...BW PREV LONG TERM....AL

000 FXUS65 KLKN 202115 AFDLKN Area Forecast Discussion National Weather Service Elko NV 215 PM PDT Mon Mar 20 2023 .SYNOPSIS...Winter weather will return for much of central and northeastern Nevada Tuesday into Wednesday as a strong storm system moves through the region. Precipitation will begin across southern Nevada Tuesday morning reaching northern NEvada by the afternoon along with bringing some gusty winds. A wintry mix is likely in some valleys to begin the event but by Tuesday night into Wednesday, snow will be the primary precipitation type. Impactful snow amounts are expected in many valleys as well as more than a foot of snow in mountain areas across the area through Wednesday afternoon. Light showers will linger across northeast Nevada through the end of the week along with well below normal temperatures. && .SHORT TERM...Tonight through Wednesday night. Convective snow shower activity associated with an exiting upper- level trough will linger across northern Nevada including the I-80 corridor through the late afternoon hours before diminishing tonight. Brief moderate snow is expected but accumulation will be minimal but could create temporary slick spots on roads. Breezy post-frontal west-northwest winds of 20-25 mph will diminish through the evening hours. The next big change will be a strong low pressure system with plenty of moisture and cold air. A more southerly trajectory of this weather feature across the Mojave Desert will cause precipitation to begin across northern Nye county beginning Tuesday morning and expand and intensify northward as the the day progresses. Snow levels will be highest during the day across central Nevada in the 5800-6100 foot range for most areas so a wintry mix or even rain is likely during the day on Tuesday in lower valleys after starting out as a lighter snow Tuesday morning. Tuesday evening will see a transition to all snow to all valleys within the widespread precipitation shield over much of the state. Considerable snowfall for March standards is expected especially across the mountains of central and northern Nevada with a foot or more likely in the higher ranges of central Nevada and the Ruby Mountains where winter storm warnings are now in place. There is still some uncertainty in valley snow amounts and will be very elevation dependent. There is still a large spread of potential snow amounts (i.e. a range of 0.3-5" in Elko, 0.5-5" in Eureka for the 10th to 90th percentile ranges). Nonetheless, this will be an impactful storm for the state with widespread snow, adding to already near record snow year. THe high end snow amount (90th percentile) from the NBM is close to one foot on some of the summit passes along US-50 east of Austin. Winds will be another issue for Tuesday especially across northern Nye county and White Pine county where the most snow is expected overall. South to southeast winds will increase considerably during the day Tuesday creating areas of blowing snow at higher elevations and passes along with general wind concerns with higher profile vehicles along east-west routes. Wind speeds of 25-35 mph with gusts of up to 50 mph are expected in some locations. Snow intensity will taper off Wednesday but lingering snow showers will persist across much of the area. Some mountain snow showers will remain Wednesday evening and night across eastern Nevada but most of the snow will have diminished as the main upper-level forcing trough moves out of the region. .LONG TERM...Thursday through next Monday Bottom line: The long term is still expected to be active, but there is still question as to what happens through the weekend and into next week. Early Thursday morning sees showers from the Tuesday - Wednesday system taper off, but wrap-around moisture and another disturbance moving through helps to support shower activity in portions of northern Nevada. Various outputs from model cluster combinations have a fair amount of agreement about the troughing pattern in the 24 hour period ending at 00Z Saturday (5PM local time on Friday), but beyond that sees agreement fall apart. However, it is worth noting that all of the cluster solutions suggest that this progressive pattern continues through the long term. From THursday morning through Friday morning, snowfall totals in the ensemble median (50% probability) shower less than half of an inch in Elko county valleys, up to an inch around the Jarbidge area, and up to 5 inches in the mountain tops. With the cluster consensus still fairly cohesive, Friday continues to see the troughing pattern and light snow showers mainly in northern Elko county. With a lack of moisture aloft, the 50% probabilities reflect less than an inch in valleys, up to an inch in higher valleys around the Jarbidge area, and up to 4 inches in the highest peaks. The important takeaway for Thursday and Friday is that showers are on track to stay well north of the Diamond Valley area where there have been significant flooding concerns lately. As mentioned, guidance isn`t in sync with the weekend and into next week. However, with a progressive and "always changing" pattern aloft, it`s reasonable to say that shower activity remains in the region. Where that activity will be, and what kind it will be is difficult to say at this time. Below normal temperatures continue as well. Thursday is expected to be the "warmest" day of the long term with highs mainly in the upper 30s and low 40s, but trend cooler through the rest of the period and reaching the 20s and 30s. Overnight lows reflect this trend with lows in the teens and single digits by the end of the week. && .AVIATION... && .HYDROLOGY...A Flood Watch remains in effect through Wednesday afternoon for southern Lander/Eureka and White Pine counties, as well as northern portions of N. Nye County. Areas of overland flooding, ponding of water in normally dry wash areas and crossing roads, washed out roads, and muddy conditions continue across portions of central Nevada. A break in precipitation will occur tonight along with temperatures dropping well below freezing in the teens mitigating further snowpack melt. A stronger storm system is expected to impact the state Tuesday and Wednesday but primary precipitation type will be snow. This will add to an already existing much above normal snowpack, in some cases more than one foot of snow, especially in the higher mountain ranges of central and northeastern Nevada. Below normal temperatures and prolonged hard freezes overnight will persist through the rest of the week. No river and stream flooding is forecast at this time. && .LKN Watches/Warnings/Advisories... Winter Weather Advisory until 5 PM PDT this afternoon Ruby Mountains and East Humboldt Range. Winter Storm Watch from late tonight through Wednesday afternoon ABOVE 6000 FEET in Northeastern Nye County...Northwestern Nye County...Ruby Mountains and East Humboldt Range...White Pine County. Flood Watch through Wednesday afternoon Northeastern Nye County...Northwestern Nye County...Southern Lander County and Southern Eureka County...White Pine County. && $$ 93/84/84