700 FXUS66 KSEW 022218 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 318 PM PDT Tue Sep 2 2025 .SYNOPSIS...High pressure will continue to build over the region, maintaining warmer and dry conditions across Western Washington through midweek. This will bring above normal temperatures to the region and Moderate to Major HeatRisk to the Cascade valleys, as well as elevated to critical fire weather conditions in the mountains. Monsoonal moisture may bring isolated shower or thunderstorms chances late in the week, with a cooler pattern likely arriving into the weekend. && .SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/...As expected, the lingering stratus has cleared across the region this afternoon. While temperatures continue to climb through the lower to mid 70s across most of the interior, it`s worth noting the very warm conditions evident across some of the higher elevations of the Olympics and Cascades, as well as in the Cascade valleys, with temperatures in the upper 70s to upper 80s in the higher elevations. Expect Moderate to local Major HeatRisk due to the combination of hot days and mild nights for the Cascade valleys, with the heat advisory continuing for these areas as a result. Dry and unstable conditions will lead to critical fire weather conditions in the Cascades as well, with more details in the Fire Weather section below. An embedded disturbance will bring some relief and a deeper push of clouds on Thursday to much of the area, though some of this relief may be more limited in portions of the Cascades. This may spread additional moisture north into western Washington to even support an isolated thunderstorm into the region, though this potential is low (less than 15 percent) and continues to decrease. && .LONG TERM /FRIDAY THROUGH TUESDAY/...Ensemble guidance continues to suggest a shift in the pattern late in the week with a broad upper trough emerging over the northeastern Pacific basin. This should bring a return of near to below-normal temperatures and increasing cloud cover and precipitation chances through the start of next week. As this mosrcontinues to increase, will see rain chances increase a bit as various disturbances rotate through the region. However, confidence in pinpointing timing and location of these features remains quite low at this time. && .AVIATION...An upper level low will continue to retrograde northwestward through the day, with a weak high/ridge tilting northwestward over the region into B.C. tonight/Thursday. The flow is very weak aloft, but will turn more from southerly to southeasterly. Down at the surface, weak high pressure remains over southwest B.C. with a surface trough to the east. VFR conditions will continue this afternoon (with a few low cloud areas remaining in the west Strait of Juan de Fuca area). Some haze aloft has been observed due to wildfire smoke. Another marine push is expected to bring stratus inland up to the interior Wednesday morning. For the interior: 30-40% chance of MVFR CIGs, with a 20-30% chance of IFR, and a 10-15% chance of LIFR. West of the interior/Puget Sound, chance of IFR is around a 60-80% (90% along the coast), and a 30-50% chance of LIFR. The chance of low VIS is less than 20% for less than 5 mi in the interior, but much higher along the coast (30-50% less than 1 mi). Low CIGs/VIS will clear late Wednesday morning into the early afternoon. North winds 5 to 10 kt (couple gusts to 15 kt possible along the waters) today will decrease down to 4 to 8 kt tonight, and increase to 5 to 10 kt Wednesday. KSEA...VFR through tonight, with lower CIGs likely Wednesday morning (20% chance it`s down to IFR and 10-15% chance of LIFR). Will become VFR late Wednesday morning/afternoon. Winds out of the north 5 to 10 kt through tonight, likely decreasing to under 5 kt and increasing to 4 to 8 kt Wednesday. HPR && .MARINE...Weak high pressure will remain in place just along the coastal waters through Thursday. With weak flow/onshore flow, there is an increased chance of low fog along the coastal waters and portions of the Strait of Juan de Fuca Wednesday morning, with around a 40% chance of these areas seeing visibilities tonight less than 1 mi. A couple of westerly pushes through the Strait of Juan de Fuca will occur this week, the strongest of which is expected Wednesday night into Thursday with the HREF giving a 50% chance of sustained winds exceeding 20 kt. The high will then weaken Friday and Saturday with a low pressure system moving into the offshore waters. A separate surface trough will remain east of the Cascades through the weekend. 3-4 ft seas tonight will bump to 4-6 ft Wednesday into Friday, decreasing back to 3-4 ft through the weekend into next week. HPR && .FIRE WEATHER...Continued warmer and drier conditions will develop through Wednesday under high pressure. While marine influence will continue to provide for excellent RH recoveries in the lowlands, expect to see continued poor recoveries in the mid-slopes and ridges in the Cascades (as well as the Olympics today). With this continued concern for poor recoveries, very dry conditions Wednesday, and increasing instability, have upgraded to a Red Flag Warning for Wednesday for fire weather zones 658 and 659. This will be the primary fire weather concern for the week, with a return to cooler conditions with a deeper marine layer later in the week. There is the potential for some monsoonal moisture to arrive and perhaps lead to a few isolated showers or thunderstorms late in the week, but confidence remains low with respect to the specifics. && .SEW WATCHES/WARNINGS/ADVISORIES... WA...Red Flag Warning from noon to 9 PM PDT Wednesday for West Slopes of the Central Cascades Generally above 1500 Feet- West Slopes of the North Cascades Generally above 1500 Feet. Heat Advisory until 5 PM PDT Thursday for Foothills and Valleys of Central King County-Foothills and Valleys of Pierce and Southern King Counties-Foothills and Valleys of Snohomish and Northern King Counties-Foothills and Valleys of Thurston and Lewis Counties-Foothills and Valleys of the North Cascades. PZ...None. && $$

288 FXUS66 KPQR 022203 AFDPQR Area Forecast Discussion National Weather Service Portland OR 303 PM PDT Tue Sep 2 2025 .SYNOPSIS... High pressure strengthening inland through midweek will bring hot weather to much of the region, with valley highs near 90 degrees and warm overnight lows in the 60s. HeatRisk will be Moderate in most areas, with pockets of Major HeatRisk in the Gorge and Hood River Valley. An upper low moving north from California will trigger scattered showers and isolated thunderstorms this evening and again Wednesday, mainly near the Cascades. By the weekend, a shift in the weather pattern will favor cooler temperatures and an increasing chance for showers. && .SHORT TERM...Now through Thursday Night...The upper low that kept conditions cooler over the Holiday weekend is drifting west into the Pacific, while upper ridging expands northward from the Great Basin. Meanwhile, a compact disturbance offshore of California is forecast to move inland tonight and into Oregon early Wednesday, providing the lift necessary for showers and isolated dry thunderstorms along the Cascades through midweek. Inland valleys will rise into the upper 80s to low 90s today, with the Columbia Gorge and Hood River Valley reaching the mid to upper 90s. The coast remains cooler in the 60s to 70s. Warm nights will provide little relief, with lows generally in the mid to upper 60s in the Willamette Valley and Cascade foothills, near 70 in the Gorge, and 50s to low 60s elsewhere. This combination of hot afternoons and warm nights will generate widespread Moderate HeatRisk, with localized Major HeatRisk in the Gorge and Hood River Valley. A Heat Advisory remains in effect for these areas through Wednesday evening. Dry thunderstorm chances will focus on the Cascades - starting mainly in Lane and Linn County Cascades, then expanding northwest into north Oregon Cascades this evening into early Wednesday morning. Additionally, southeasterly flow aloft may push thunderstorms to the west overnight, affecting the southern Willamette Valley and inner coastal waters near Newport, OR. Wednesday morning into the afternoon, thunderstorms will be mostly confined to the northwest Oregon Cascades. Given the dry subcloud layer, lightning without much rainfall is possible, raising concerns for dry strikes. By Thursday, the low begins to weaken and lift north, leading to fewer storms and slightly cooler temperatures. Cloud debris or showers may also limit daytime heating in places. Note, thunderstorms may still remain possible on Thursday, but confidence remains low at this time. .LONG TERM...Friday through Monday...By late week, forecast ensembles show a shift toward troughing over the northeast Pacific, ending the hot pattern and steering temperatures back toward seasonal levels. Cooling is expected to continue into early next week, with some areas trending below normal. The broad offshore trough should also bring increasing moisture and improve chances for showers, particularly along the coast and Cascades. While details remain uncertain, the overall signal points toward a cooler and potentially wetter stretch developing from the weekend into next week. ~Hall && .AVIATION...VFR conditions expected for the next 24 hours at inland sites. Along the coast, VFR conditions until marine stratus forms once again overnight. Expect MVFR/IFR ceilings to form at KONP by 00-04z Wed, slowly spreading north along the coast to form at KAST by 07-11z Wed. Ceilings should return to VFR conditions by 16-20z Wed with daytime heating. Mainly northwest winds along the coast, increasing to around 10 kts after 19z Tue, with gusts up to 20 kts around KONP through around 00-03z Wed. Inland winds generally light from the north to northwest. A weather system will begin producing shower and thunderstorm chances over the central Oregon Cascades after 00z Wed. Some showers and possibly a thunderstorm could be possible into the Willamette Valley after 10z Wed. Current thunderstorm probability is less than 10% chance at any valley terminal, so no mention in the TAFS, but have included VCSH in KEUG TAF. These chances could spread north to KSLE by 16-19z Wed, but probability is too low to add to TAF at this time. Winds will also shift west to southwest in the southern Willamette Valley at this time. PDX AND APPROACHES...VFR conditions next 24 hours. Winds stay fairly light out of the northwest. -HEC && .MARINE...Fairly benign late-summer like conditions are expected through the rest of the week into the weekend. A weak surface low pressure off southwest Vancouver Island gradually moves westward the next several days with high pressure strengthening across the coast waters. This progression will tighten surface pressure gradients, allowing for increasing northerly winds during the afternoon and evening hours, especially on Wednesday and Thursday. Peak wind gusts during the mid-week period likely sit in the 15-20 knots range with probabilities for small craft conditions of gusts over 21 kts only around 10-20%. Seas increase to around 4-6 ft this afternoon due to an increase in wind waves and a fresh northwesterly swell. Expect seas to hold in this 4-6 ft range through Friday before backing off slightly over the weekend into next week. -Schuldt/HEC && .FIRE WEATHER...A low pressure system lifting north from California into Oregon on Wednesday and Washington by Thursday will bring a heightened risk for dry thunderstorms. Southeasterly flow aloft will increase lift and instability while surface conditions remain dry, with relative humidity bottoming out near 20-30% along the Cascades and 30-40% in the foothills. This setup will favor thunderstorm development over the Oregon Cascades this evening, with activity drifting into foothills and valley locations overnight. High cloud bases will allow much of the rainfall to evaporate before reaching the ground, making dry lightning and gusty, erratic outflow winds possible. While slower-moving storms could bring localized rain, lightning strikes may extend well away from rain cores. Given the very receptive fuels, new fire starts are possible, especially in the Willamette NF where a Red Flag Warning continues for Zones 689 and 690. Strong instability may also enhance pyroconvective activity for ongoing fire. By Wednesday, the low weakens as it tracks farther north, lowering confidence in widespread dry lightning. However, elevated instability will persist in southeastern Lane County, supporting the extensions of the Red Flag Warning through 9 PM Wednesday. To the north, a Red Flag Warning has been issued for Zones 634, 635, and 688 - including the Mt. Hood and Gifford Pinchot NFs from 12 PM to 9 PM Wednesday. ~Hall && .PQR WATCHES/WARNINGS/ADVISORIES... OR...Red Flag Warning from noon to 9 PM PDT Wednesday for ORZ688. Heat Advisory until 9 PM PDT Wednesday for ORZ120>122. Red Flag Warning until 9 PM PDT Wednesday for ORZ689-690. WA...Red Flag Warning from noon to 9 PM PDT Wednesday for WAZ634- 635. Heat Advisory until 9 PM PDT Wednesday for WAZ209-210. PZ...None. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland x.com/NWSPortland

492 FXUS66 KMFR 022149 AFDMFR Area Forecast Discussion National Weather Service Medford OR 249 PM PDT Tue Sep 2 2025 .DISCUSSION... -Hot temperatures and thunderstorms will be the primary concerns through Thursday. -Thunderstorm potential continues into the weekend but temperatures trend cooler from Friday onward. -Smoke and haze will continue to bring periods of degraded air quality to the region, worst in the vicinity of ongoing wildfires. -Early next week, upper level trough likely moves over the region, potentially bringing below normal temperatures and the chance for light, but beneficial rainfall. High pressure will amplify over the Intermountain West this week as strong low pressure dives southward over the eastern CONUS and low pressure lingers over the eastern Pacific. Meanwhile, there will be two weak, negatively tilted, shortwave troughs that move northward through the region along the western periphery of the ridge. The first is approaching the area this afternoon and is expected to be north of the region by Thursday morning. The next swings through Friday into early Sunday. With the ridge amplifying, hot temperatures are expected today through Thursday. With temperatures expected to be 10 to 15 degrees above normal temperatures during this time, there will be a moderate risk for heat related illnesses. There could be period this afternoon when there a major risk of heat related illnesses in the Rogue Valley, but the overall impact in the region will mainly be for those who are sensitive to these temperatures, especially those without adequate cooling/hydration. Afternoon temperatures look to remain fairly steady today through Thursday with high temperatures in the upper 90s (80s)/low 100s (90s) for valleys west (east) of the Cascades. Cloud cover from anticipated thunderstorms (more on this below) could keep temperatures a few degrees cooler here and there, but not enough to really notice. Even still, guidance shows the probability of reaching or exceeding 100 degrees today (for Medford) around 90% whereas that probability drops to around 50-60% for Wednesday and Thursday. Temperatures trend cooler Friday into the weekend, but will still remain above normal until late weekend/early next week. Thunderstorms...the first of two negatively tilted shortwaves is approaching the region this afternoon as noted by the high level clouds moving into the area. Overnight and earlier this morning, as this shortwave moved northward through the Sacramento Valley, it kicked off thunderstorms overnight and produced a fair amount of lightning. This shows that the elevated instability is there. Models have come into better agreement regarding how fast the trough exits the region, but slowed the arrival a bit. This slow down now means there is a better chance for some overnight shower/thunderstorm activity tonight. Before then however, we expect isolated to scattered thunderstorms in the area this afternoon and evening, focused along/east of the Cascades and across northern California. Storm motion is forecast to be around 15-25 kts, which is sufficient for storms to move off the terrain. Additionally, storm motion will generally be from the south to southeast, which is favorable for storms to move off the Siskiyous into the Rogue/Illinois/Applegate Valleys this evening. The fly in the ointment, however, is the area of cloud cover currently moving into the region, and to some degree the amount of smoke around. Cloud cover has been known to limit surface heating/instability and smoke can choke out thunderstorms as well. With these two factors present this afternoon, it`s possible that thunderstorm activity isn`t as widespread as what is currently forecast. Overnight tonight, guidance maintains some isolated shower/thunderstorm potential over the region. The majority of the high resolution models are bringing a band of showers that stretches across Modoc/southern Klamath/central Jackson Counties northeastward into the Umpqua Basin by the early morning hours. The probability of thunder is pretty low in the CAMs, but given the activity seen in the Sacramento Valley last night, we`ve maintained a thunder mention in the forecast for the overnight period. Thunder chances continue into Wednesday as the trough moves overhead. With the timing of the trough, it could be one of those days where storms are firing off a little earlier in the day compared to normal. Expected another day of isolated to scattered thunderstorms that should wind down after sunset. Overnight chances Wednesday look to be less with the trough moving just north of the forecast area Wednesday night. We should see a relative lull in storm activity on Thursday. The GFS maintains some energy and instability on Thursday, but looks to be less than today and Wednesday, so storms should be more isolated. Friday into the weekend, temperatures will trend cooler but still remain above normal for early September (normal high for Medford being 88 degrees). Upper level troughing will be persistent over the eastern Pacific and we`ll see additional shortwave troughs pass through the region through the weekend. The next is expected to approach the region Friday, bringing the return of scattered thunderstorm chances Friday into Saturday. It`s a bit early to try to pinpoint details at this time, but current guidance indicates thunderstorms possible as far west as the coast with this shortwave. Stay tuned for updates as details become more clear. Beyond Saturday, the parent trough over the eastern Pacific responsible for sending these shortwaves through the area moves closer to the West Coast. While it`s too early to say with confidence, models generally agree on this trough moving inland through Oregon, bringing below normal temperatures and chances of light, but beneficial precipitation. This by no means looks like a season ending event with the current forecast only having around a tenth of an inch of rain in the forecast, but certainly a system to moderate fire weather concerns. There are differences in the guidance and ensembles on the timing of this beneficial rainfall, with some saying early next week and others saying more towards the middle of next week. Again, stay tuned for updates and/or changes to the forecast as the time gets closer. /BR-y && .AVIATION...02/18Z TAFs...Along the coast, VFR prevails today, with the exception of the near-shore waters and immediate coastline south of Gold Beach, where marine layer stratus/fog persists. Expect stratus/fog to return to the coast and the coastal valleys again this evening and tonight. Moisture returning from the south and east this afternoon/evening will lead to isolated to scattered thunderstorms. Best probability for a thunderstorm is at Klamath Falls, but one could occur at Medford/Roseburg too. Thunderstorm activity may continue overnight along and east of the Cascades. Gusty outflow winds and periods of reduced flight conditions can be expected with any thunderstorms that occur over the next 24 hours. Otherwise, VFR will prevail. Smoke from area wildfires isn`t expected to result in lower flight conditions for most locations, except in the immediate vicinity or just downwind from wildfires, but brief periods of lower visibility and/or haze are possible. -BPN && .MARINE...Updated 100 PM PDT Tuesday, September 2, 2025...Northerly winds will persist this week. Winds and seas will hover at advisory levels south of Cape Blanco through Wednesday night. Conditions are expected to improve for the latter half of the week as winds ease and seas lower. /BR-y && .FIRE WEATHER...Updated 200 PM PDT Tuesday, September 2, 2025...A shortwave travelling along the southwest flow aloft has produced numerous thunderstorms across California this morning and early this afternoon. This wave will continue to push north, and will pass over far northern California and southern Oregon this afternoon. This impulse should be able to tap into the hot temperatures and increasing moisture to produce unstable conditions and thunderstorms over much of the area today. Models continue to show the most likely area of thunderstorm development to be from the Cascades east and Siskiyous south this afternoon and evening. A Red Flag Warning remains in effect for these areas due to the potential for abundant lightning on dry fuels. There is a potential for south/southeast to north/northwest steering flow pushing isolated storms off terrain and into portions of the Rogue and Umpqua basins this evening. Then, with the impulse still overhead, thunderstorms could linger along and east of the Cascades through tonight and into the early morning hours. Any nocturnal storms are likely to be high based, and therefore are much more likely to be dry. Instability will redevelop over portions of the area Wednesday afternoon, with scattered thunderstorms possible yet again, but this time mainly focused along the Cascades, the Warners, and other areas of high terrain of the Eats Side. Aside from the threat of lightning, models soundings show a very dry low layer (inverted "V" sounding) which means storms that do form will likely produce strong, gusty and erratic outflow winds (35-50 mph) and may produce little to no rainfall. Additionally, today will be the hottest day of the week, and with dry low level humidities and breezy afternoon winds, we may see some locations approach but not quite pass critical thresholds. The hot temperatures, dry RH, breezy afternoon winds, and overall instability will add to the already heightened fire weather concerns due to lightning. Isolated thunderstorms are possible Thursday, again along and east of the Cascades, as the influence from the larger upper level trough to our west continues. Friday into Saturday, a low nears the coast and passes onshore, resulting in cooler, more seasonable temperatures, and additional chances for showers and thunderstorms over inland areas Saturday. -BPN && .MFR WATCHES/WARNINGS/ADVISORIES... OR...Red Flag Warning until 9 PM PDT this evening for ORZ617-621- 623>625. CA...Red Flag Warning until 9 PM PDT this evening for CAZ280-281-284- 285. PACIFIC COASTAL WATERS...Small Craft Advisory until 5 AM PDT Thursday for PZZ356-376. && $$

916 FXUS66 KEKA 022216 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 316 PM PDT Tue Sep 2 2025 .SYNOPSIS...Isolated dry thunderstorms remain possible in the interior late this afternoon and evening. Hot temperatures likely through Wednesday for the interior. Stratus likely for the coastal areas with marginal short-lived clearing in the afternoons for the coming days. Another upper level low/trough will bring a slight chance of showers, perhaps some thunderstorms, across the northern portions of the area Thursday and Friday. && .DISCUSSION...An upper level low/trough continue to approaches slowly from the south today, while moisture has surged across the area. Radar imagery showed showers from southeast moving across Trinity County, while surface observations reported few hundredths of an inch. Cloudiness will continue to diminish from south to north during the next hour or so, allowing a surface heating with high temperatures rapidly climbing to mid 90`s and reaching or exceeding 100F across the interior. The progressive aforementioned disturbance will bring an increasing instability and breezy winds late this afternoon and evening. Breezy easterly winds have been developed with gusts from 25 to around 30 mph over the higher terrain. Dry low levels and DCAPE over 1000 J/kg support gusty outflow winds of up to 40-60 mph for any storms that do form. Tonight, lingering chances (15%) of showers and thunderstorms are expected over the northeastern portion of Trinity County with showers as the trough continue to move northward. CAMs show weak returns over the Trinity Horn while moderate to strong returns farther east and north of the area. On Wednesday, the shortwave disturbance begins to move northward and the weather quiets down. An approaching upper level trough is expected to gradually approach the area from the west pushing the warmer air ridging off to the east. This may help to weaken the low level inversion, allowing a period of clearing skies long the coastal areas. Thursday and Friday, an upper level low/trough will approaches the area. The winds aloft shift to the southwest. This will bring a slight chances (10-20%) of showers across the northern portion of the forecast area, especially for Del Norte County. GFS and NAM suggest an increasing instability over interior Del Norte and northern Trinity counties on Thursday and Friday. Sounding models show elevated instability with an inverted V over Trinity County on Thursday. Temperatures are expected to diminish by a degree or two in most areas and another few degrees Thursday. On Friday and Saturday, more significant cooling is expected with interior highs in the high 80`s to low 90`s Friday and the 80s mainly on Saturday. The coastal inversion will be fairly weak by this point and it may allow the coast to clear out allowing weekend temperatures in the mid 60s. /ZVS && .AVIATION...18Z TAFs)...Stratus offshore continues to impact the coastal terminals late this morning. Some lifting and scattering is already occurring around ACV, and this is likely to continue into the afternoon hours. Light onshore winds will support stratus remaining right off the coast with brief IFR impacts possible into the evening. An eddy offshore continues to reinforce stratus at CEC, so confidence is lower on significant improvement at CEC this afternoon. Some brief clearing is still possible, but it will be short lived. Most models are suggesting a shallow marine layer again this evening and overnight, with LIFR ceilings and visibilities. There is some uncertainty as an area of low pressure moves overhead, which may deepen the marine layer slightly and raise ceiling heights from what is forecast. Still this may only raise ceilings from LIFR to IFR. The interior areas, including UKI, remain VFR with mainly high clouds and breezy winds this afternoon. Thunderstorm activity is like to remain to the north and east this afternoon and evening, primarily in Trinity and Siskiyou Counties. JB && .MARINE...Northerly winds continue with gusts up to 25-35 kts possible in the lee of Cape Mendocino this afternoon. The outer waters north of the Cape forecast to see wind gusts of around 15-20 kts, while nearshore areas continue to see light winds. Seas remain steep in the outer waters. A brief lull is possible this evening and overnight north of Cape Mendocino, but steep waves of 6-7 ft return by Wednesday morning. The strong winds in the lee of the Cape start to ease somewhat tonight into Wednesday as a low pressure system moves up from the south. Still, northerly gusts of 15-20 kts are likely in the outer waters Wednesday afternoon. By Thursday, a broad trough approaches the area from the north which finally eases the northerly winds, especially north of Cape Mendocino. A series of shortwaves late week into the weekend will maintain milder conditions conditions. Winds may turn southerly at times, depending on how far south the trough dips. JB && .FIRE WEATHER...Temperatures climbing rapidly to above normal across the interior as the surge of moisture continues to move northward and the sky clear out from south to north. There remain slight chance (15%) of isolated dry thunderstorms in the interior through this evening with increasing instability this afternoon and evening, primarily for Trinity County. Diurnal, terrain driven winds forecasted with breezy afternoon winds outside of any gusty winds from thunderstorms. Gusty and erratic outflow winds of 40 to 60 mph are possible with any storms that do form. Even if no storms form, fire danger is expected to increase. The overall atmospheric instability will increase ventilation/mixing allowing for more fire growth and the potential for plume dominated potential. The high mixing heights will also mix down wind gusts of 25 to 30 mph in the higher terrain and exposed areas. A Red Flag Warning remain in effect until 8PM PDT this evening for Fire Weather Zones 204 and 283. Winds trend downward Wednesday, but warm temperatures and very low afternoon RH with poor overnight recoveries in the high elevations are forecast to continue through Thursday. An approaching upper level low/trough will bring a slight chances (10-20%) of precipitation across the northern portion of the area Thursday and Friday. This will bring an increasing instability, with the potential of isolated thunderstorms across interior Del Norte and northern Trinity counties. Cooler weather with below normal temperatures and generally higher relative humidity is expected for this weekend. && .EKA WATCHES/WARNINGS/ADVISORIES... CA... Red Flag Warning until 8 PM PDT this evening for CAZ204-283. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 11 PM PDT this evening for PZZ455. Small Craft Advisory until 3 PM PDT this afternoon for PZZ470. Small Craft Advisory from 3 AM Wednesday to 3 PM PDT Thursday for PZZ470. Small Craft Advisory until 3 PM PDT Thursday for PZZ475. && $$ NOTE: The full forecast discussion is now regularly issued between 10 am/pm and 1 pm/am. Additional updates will be issued as needed. 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

923 FXUS66 KMTR 022338 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 438 PM PDT Tue Sep 2 2025 ...New AVIATION, MARINE... .KEY MESSAGES... Updated at 238 PM PDT Tue Sep 2 2025 - A non-zero (10-15%) chance of isolated showers and thunderstorms continues through this afternoon along the interior eastern portions of Contra Costa, Alameda, Santa Clara, San Benito, and Monterey Counties. - Gradual cooling trend through the remainder of the week. && .SHORT TERM... Issued at 238 PM PDT Tue Sep 2 2025 (This evening through Wednesday) Thunderstorm chances are diminishing across the CWA due to an influx of drier air into the middle and upper levels of the atmosphere. Satellite imagery shows the cut-off low located just off the coast from San Mateo County down to Monterey County with guidance showing the cut-off low progressing inland and weakening late tonight into tomorrow. As the low approaches our coastline, it is transporting much drier air into the middle and upper levels of the atmosphere along the coastline (shown quite well in the Mid-level water vapor satellite imagery). Aircraft soundings from SFO, OAK, and SJC all show RH values dropping in the mid and upper levels of the atmosphere between early this morning and this afternoon. The most recent SJC aircraft sounding (taken at 2030Z or 1:30 PM PDT) shows mid level-RH values around 31% and high level RH values between 17% to 29%. Comparatively, mid to high level RH values were closer to 45% around 4AM to 5AM PDT this morning at SJC when thunderstorms were observed across eastern portions of Santa Clara County. A look at SPC mesoscale analysis shows a corridor of higher CAPE values across the Central Valley while CAPE values are much lower (~500- 1000 J/kg) across the Bay Area and Central Coast. Given the instability present, there continues to be a non-zero chance that an isolated thunderstorm may develop along the far easternmost portions of Napa, Contra Costa, Alameda, Santa Clara, San Benito, and Monterey Counties. The incoming dry air mass has helped to prevent more widespread convection from developing across our CWA with High Resolution convective allowing models (CAM) showing thunderstorms staying well to our east over the Sierra Nevada Range. A non-zero (10-15%) chance of thunderstorms will thus continue through the remainder of the afternoon across the easternmost portions of the Bay Area and Central Coast. Tuesday night into Wednesday, the offshore cut-off low will weaken and weak troughing will persist along across the coastline. This will help kick off a cooling trend for the Bay Area and the Central Coast. Temperatures will cool by 2-4 degrees on Wednesday with highs in the 80s to low 90s across the interior and in the 60s to low 70s along the coastline. Weak upper-level troughing will help to keep the marine layer deeper (~1500-1800 ft) which will allow widespread stratus along the coast and across the interior tonight. Patchy coastal drizzle is expected tomorrow morning with max accumulations of a few hundredths of an inch possible. && .LONG TERM... Issued at 238 PM PDT Tue Sep 2 2025 (Wednesday night through next Monday) Weak upper level troughing continues through the end of this week with another upper level trough building in over the weekend and into next week. This will allow our gradual cooling trend to continue Thursday into Friday with temperatures stabilizing near normal over the weekend. High temperatures will be in the 80s to low 90s on Thursday before dropping into the 70s to low 80s Friday through Monday. Coastal drizzle is expected Thursday morning and again Friday morning as persistent upper level troughing maintains a a deeper marine layer around 1000 to 1500 ft. CPC shows near normal temperatures and slightly above normal precipitation continuing through mid-September. As noted by the night shift, however, September is still part of our region`s dry season with most locations seeing no rain from late spring into the fall. Any accumulating precipitation, even that of a few hundredths of an inch, would therefore be considered above normal for our region. && .AVIATION... (00Z TAFS) Issued at 438 PM PDT Tue Sep 2 2025 Some MVFR-IFR stratus lingers at the immediate coastal areas with VFR conditions inland. Breezy onshore winds will continue through the the afternoon and evening hours, before diminishing later in the evening. A very low chance (around 10-20% probability) of convection remains in the far interior through the next couple of hours, but will end after sunset. Overnight, stratus will expand into the inland valleys and drop to a generally IFR-LIFR ceiling, with low to moderate confidence of stratus impacting the interior. Stratus will retreat to the immediate coastal region through Wednesday morning, with breezy onshore winds resuming in the afternoon. Vicinity of SFO... VFR through the evening with breezy southwest winds through the evening. MVFR-IFR stratus returns to the terminal overnight with moderate confidence in timing, with stratus flow through the Golden Gate potentially setting up to the north of the terminal. Stratus will clear late Wednesday morning before breezy west winds return in the afternoon. Low to moderate confidence in stratus returning Wednesday night, with higher confidence in stratus returning to OAK before the end of the TAF period. SFO Bridge Approach... Similar to SFO. Monterey Bay Terminals... MVFR-IFR stratus has lingered to the north of the terminals with a potential for imminent impacts to SNS. In any case, VFR conditions will only continue for the next couple of hours with IFR-LIFR conditions overnight. Stratus will gradually retreat to the immediate coast on Wednesday morning, with potential for stratus to return to MRY at or shortly after the end of the TAF period. Breezy onshore winds will continue through the evening hours, becoming light overnight with the onshore winds resuming Wednesday afternoon. && .MARINE... (Tonight through next Sunday) Issued at 438 PM PDT Tue Sep 2 2025 Northwesterly breezes will continue to diminish today, with moderate to fresh breezes prevailing through Friday. Strong northwesterly gusts will result in hazardous conditions for small craft on Wednesday across the outer waters and coastal jet regions. Moderate seas will prevail through Friday with occasional rough seas in the outer waters. && .FIRE WEATHER... Issued at 156 AM PDT Tue Sep 2 2025 An upper level low continues to move northeastward passing over the region today. The low is surrounded by some drier air off shore, but has started to tap into residual mid level moisture this morning. The primary concern is there is a low, 15-20%, chance of high impact weather if any elevated showers, isolated dry lightning and storm associated gusty outflow winds develop. The best chances look to be across our interior and most eastern regions, favoring Contra Costa, Alameda, Santa Clara, San Benito, and Monterey counties. For interior portions of the North Bay, chances are less than 10%, but will still be monitored. Otherwise a cooling trend sets in Tuesday and will continue through the remainder of the extended forecast. Daily highs and lows will be closer to normal for early September. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...Small Craft Advisory until 3 AM PDT Wednesday for Pt Arena to Pt Reyes 10-60 NM. && $$ SHORT TERM...Kennedy LONG TERM....Kennedy AVIATION...DialH MARINE...DialH Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, X, and YouTube at: www.facebook.com/nwsbayarea x.com/nwsbayarea www.youtube.com/nwsbayarea

753 FXUS66 KOTX 022154 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 254 PM PDT Tue Sep 2 2025 .KEY MESSAGES... - Hot temperatures this week (especially through Wednesday and Thursday), locally near 100, with major to locally extreme HeatRisk. Record high temperatures for September possible for multiple locations. - Breezy northeast winds for Idaho and portions of the Columbia Basin Thursday evening into Friday. && .SYNOPSIS... High temperatures will climb into the upper 90s to near 100 degrees through much of the work week. && .DISCUSSION... HOT WEATHER WITH WIDESPREAD MAJOR HEATRISK... A strong ridge will lead to record heat and dry conditions across the Inland NW for the next few days. Similar temperatures to today are expected again for Wednesday, around 20 degrees above daily normals! Try to avoid or moderate activities that could lead to heat-related illnesses. In addition, critical fire weather conditions are likely across the central Cascades of eastern WA as unstable conditions are combined with the hot and dry weather. Areas of smoke/haze are likely to continue for the next several days as well, leading to worsening air quality for many locations. `Cooler` conditions look to return by the weekend as the ridge breaks down and low pressure develops across the Pacific NW. Shower chances to return as well for the weekend and early next week, though significant widespread rain amounts don`t look likely at this time. Something to watch over the coming days. /KD && .AVIATION... 00Z TAFS: VFR conditions will prevail. Some airfields in the Cascades, northern Washington, and northern Idaho may experience periods of MVFR conditions from smoke from local fires. Otherwise, light winds and VFR conditions to prevail through the 24 hr TAF period. FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: Low confidence in MVFR or worse conditions in smoke developing at any 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:/weather.gov/otx/avndashboard && .Preliminary Point Temps/PoPs... Spokane 64 100 64 96 62 94 / 0 0 0 0 0 0 Coeur d`Alene 65 99 64 95 62 94 / 0 0 0 0 0 0 Pullman 61 97 62 94 59 93 / 0 0 0 0 0 0 Lewiston 70 103 70 100 68 99 / 0 0 0 0 0 0 Colville 55 100 54 97 52 94 / 0 0 0 0 0 0 Sandpoint 59 96 58 91 55 89 / 0 0 0 0 0 0 Kellogg 69 97 67 92 62 92 / 0 0 0 0 0 0 Moses Lake 61 102 63 99 64 96 / 0 0 0 0 0 0 Wenatchee 72 102 74 99 71 96 / 0 0 0 0 0 0 Omak 68 104 68 100 67 97 / 0 0 0 0 0 0 && .OTX WATCHES/WARNINGS/ADVISORIES... WA...Heat Advisory until 8 PM PDT Thursday for Central Chelan County-Northeast Mountains-Okanogan Highlands-Spokane Area-Upper Columbia Basin-Washington Palouse-Waterville Plateau-Western Okanogan County. Extreme Heat Warning until 8 PM PDT Thursday for Lower Garfield and Asotin Counties-Moses Lake Area-Okanogan Valley-Wenatchee Area. Air Quality Alert until 5 PM PDT Friday for Moses Lake Area- Northeast Mountains-Spokane Area-Upper Columbia Basin- Waterville Plateau. Red Flag Warning until 9 PM PDT Thursday for East Washington Central Cascades (Zone 696). ID...Heat Advisory until 8 PM PDT Thursday for Central Panhandle Mountains-Coeur d`Alene Area-Idaho Palouse-Lewis and Southern Nez Perce Counties-Northern Panhandle. Extreme Heat Warning until 8 PM PDT Thursday for Lewiston Area. && $$

793 FXUS66 KPDT 022335 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 435 PM PDT Tue Sep 2 2025 .UPDATED AVIATION DISCUSSION... .AVIATION...00Z TAFs...VFR conditions prevail through the TAF period with generally light winds. However, sustained winds of 12- 20kts may develop over KRDM/KBDN with gusts up to 30-40kts this evening (<20% confidence). Feaster/97 && .PREV DISCUSSION... /issued 217 PM PDT Tue Sep 2 2025/ .DISCUSSION...Satellite shows some haze/smoke making its way into the Pendleton area. We`ll see this persist through at least the next day. Light and variable winds will lead to less transport of the smoke. Smoke caused by the Wildcat fires is mostly responsible for the Air Quality Alert out for Kittitas and Yakima County. Going through the week, an upper level ridge over the PacNW will continue to build into the area, bringing spotty triple digit temperatures across the Basin. Temperatures will gradually warm up another 5-10 degrees through Thursday, until the ridge pushes off to the west. Extreme Heat Warnings and Heat Advisories are issued across most of the region. Central OR will cool down quicker below Major level thanks to incoming clouds and showers from an upper level low over California. This upper feature will bring showers/thunderstorms to the Central OR region through overnight tonight and every day through the middle of the week. Chances are slight (15-25% chance) of storms developing over Central OR. Storms are likely to be dry going through tonight, but will progressively become wetter as the week goes on. Expecting coverage of shower activity to expand through the Southern Blue Mountains and parts of the Foothills by late this week, giving us relief from the heat we will experience over the next couple of days. With the caveat of dry thunderstorms, a Red Flag Warning was issued for parts of Central OR through tomorrow. Unsure about Wednesday and beyond as confidence drops (>15%) on whether or not lightning will verify an event. CAMs suggest >40 dbz paintballs going through tomorrow on the southern part of Deschutes County. Coupled with low PWAT values of 0.7-0.9", a warning was issued. Through the end of the week going into next week, guidance suggest temperatures cooling to the high 70s to low 80s, although at the expense of widespread precip coverage, thanks to a trough moving ashore from the Gulf of Alaska into the PacNW. Although need to keep an eye on thunderstorm coverage going into the weekend, not anticipating anything to suggest we will see dry storm events. && .PRELIMINARY POINT TEMPS/POPS... PDT 65 99 66 97 / 0 0 0 0 ALW 70 101 72 99 / 10 0 0 0 PSC 61 101 64 100 / 0 0 0 0 YKM 65 102 68 100 / 0 0 0 0 HRI 62 100 65 100 / 0 0 0 0 ELN 61 101 65 98 / 0 0 0 0 RDM 58 93 54 95 / 10 10 20 10 LGD 61 99 63 96 / 0 0 0 0 GCD 61 96 63 95 / 10 0 10 0 DLS 68 102 68 101 / 10 0 10 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...Extreme Heat Warning until 8 PM PDT Thursday for ORZ041-044-507- 508-510. Heat Advisory until 8 PM PDT this evening for ORZ049-502-505-511. Red Flag Warning until 8 PM PDT Wednesday for ORZ705. WA...Extreme Heat Warning until 8 PM PDT Thursday for WAZ024-026>029- 521. Heat Advisory until 8 PM PDT this evening for WAZ030-523. && $$ SHORT TERM...95 LONG TERM....95 AVIATION...97

522 FXUS65 KREV 022130 AFDREV Area Forecast Discussion National Weather Service Reno NV 230 PM PDT Tue Sep 2 2025 .KEY MESSAGES... * Thunderstorm chances will continue for the rest of today with a risk for fast moving storms containing moderate to heavy rain south of Interstate 80, and dry lightning in northern Washoe County and northeastern California. * Areas of smoke and haze continue to locally impact visibility and air quality due to fires in the southern Sierra. * Thunderstorm chances persist through the end of the week, with a potential for cooler temperatures and increasing winds this weekend. && .DISCUSSION... The latest upper air RAP analysis shows the CWA between an upper low near the Bay Area to the west and an upper ridge to the east yielding a southerly flow over the CWA. Going through the day, forecast guidance shows the western low traveling into northern CA. With this setup aloft, monsoonal moisture continues to flow into the region from the south with CAMs still showing 0.6-0.8 inches of PWAT in the southern half of the CWA today with some localized areas around 1 inch. As the low moves closer to the CWA, models are showing around a 30-50% chance for showers and thunderstorms this afternoon and evening in the Sierra and Sierra Front while western NV shows around a 15-30% chance. As southern portions of the CWA (south of US-50) see a marginal excessive rainfall threat today, a Flash Flood Watch has been issued for Mono, Mineral, and Southern Lyon Counties through later tonight. Thunderstorms in these areas today are capable of moderate to heavy rainfall which could lead to localized flash flooding and mudslides. There is some concern for the Tamarack and Conner burn scars as well especially if showers and storms train over the area. CAMs though show the storms today having a south-to-north trajectory and a relatively quick storm motion. As for potential storms to the north, the current Red Flag Warning continues for areas closest to OR as there is a isolated dry lightning threat today that could start wildfires. With DCAPE values surpassing 1000 J/kg, thunderstorms in the CWA today could produce gusty outflow winds up to around 50-55 mph. The storm threat for the CWA looks to end a bit before midnight with some lingering showers continuing into tomorrow morning for areas closer to the OR border. Another concern continues to be smoke and haze from the CA wildfires particularly from the Garnet Wildfire. The latest HRRR model depicts wildfire smoke coming into Mono County tonight that travels up the Sierra and spreads into Lassen County by the Wednesday afternoon hours. There is then an eastward shift in this smoke plume by Wednesday evening as the Reno-Carson City-Virginia City-Minden areas could see some patchy smoke. While not anticipating the smoke to severely reduce area visibilities, please continue to monitor the air quality conditions at airnow.gov especially if you have outdoor plans or are sensitive to poor air quality. Going through the rest of the work week, shower and thunderstorm chances continue through Friday though they look to be a bit lesser than those chances seen today. The forecast for Wednesday afternoon calls for around a 25-40% chance for showers and storms south of US- 50. Thursday afternoon has around a 15-25% chance for precipitation across the CWA while better chances (20-40%) for precipitation look to be in western NV on Friday afternoon. Ensemble guidance continues to show a drying pattern for this weekend as well as cooler and below average daytime temperatures. The potential for increased winds has come down a little bit for the weekend with the latest NBM showing a 20-30% chance for gusts of 25 mph or more in western NV. Increased Sierra Ridge winds gusting over 30 mph are in the forecast on Monday with precipitation chances returning for northern portions of the CWA. -078 && .AVIATION... Area TAF sites look to see mostly VFR conditions today though they could be interrupted by showers and thunderstorms bringing brief periods of reduced visibility and potential gusty outflow winds up to around 40-45 kts. The current window for showers and storms today looks close around 3/04-05Z. There may be some lingering showers closer to the OR border through 3/09-10Z as well. Another aviation concern continues to be smoke from the Garnet Wildfire in CA that may reduce visibility for KMMH and surrounding areas tonight and into tomorrow. Reductions to slantwise visibility are also possible from this wildfire smoke in other portions of the region at this time. Chances for showers and thunderstorms within the area continue through Friday though currently look to have lesser chances compared to those forecast for today. -078 && .FIRE WEATHER... Showers and thunderstorms develop this afternoon as an upper low brings an increase in moisture and instability. The main activity will be over the Sierra, NE CA and Western NV. As storms tend to be more isolated further north, dry lightning and gusty outflow winds becomes more of a risk, leading to a critical fire weather pattern. Further south, the main hazards will be brief periods of moderate to heavy rainfall, small hail, gusty outflow winds greater than 45 mph, and isolated dry lightning on the edges of the heavier activity. Although moisture is high for this time of year (90% percentile), storms are expected to be fast moving, so we are not expecting the level of flooding seen last week. Shower and storm activity reduces from Wednesday and beyond to around 20% or less, although there is still the risk of dry lightning away from rain cores, heavy rainfall, and gusty outflow winds. A more breezy, but cooler pattern develops this weekend with the approach of another trough. This pattern could lead to isolated elevated concerns in mountain ridges and over NW NV and NE CA if it were to persist. -Jim/HC && .REV Watches/Warnings/Advisories... NV...Red Flag Warning until 11 PM PDT this evening NVZ458. Flood Watch until 9 PM PDT this evening NVZ001. CA...Red Flag Warning until 11 PM PDT this evening CAZ270-278. Flood Watch until 9 PM PDT this evening CAZ073. && $$

908 FXUS66 KSTO 022054 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 154 PM PDT Tue Sep 2 2025 For additional details on weather and expected impacts over the next 7 days, please visit weather.gov/sto/briefing. .DISCUSSION... .SYNOPSIS... A progressive weather system brings thunderstorm chances today through Thursday, as temperatures trend more seasonable from midweek onward. && .KEY MESSAGES... * Today - Thursday: - Weather system continues to track northward along the California coast today and Wednesday, bringing a gradual cool down and the return of periodically breezy onshore winds. - Slight (10-30%) chance of afternoon/evening isolated thunderstorms as the system moves through. - Lingering chances (10-25%) for afternoon/evening isolated thunderstorms on Thursday - Highest chances for thunderstorms occur today across the Sierra and southern Cascades. * Friday - Monday: - Broad troughing aloft expected to remain in place through early next week with slight variations in location and orientation. - Seasonable to slightly below normal temperatures forecast across interior NorCal by next weekend as breezy onshore flow persists. .Changes from previous forecast... - Slight increase in thunderstorm potential for Thursday afternoon and evening && .AVIATION... VFR conditions are expected over the next 24 hours. Winds will be generally 10kt or less, except near the Delta with winds up to 12 kt and gusts up to 15-25 kt into 18z Wed. High clouds will continue to lift north and east today with relatively clear skies returning by 14z Wed. Chances for local MVFR/IFR conditions from thunderstorms over the Sierra and Southern Cascades in the afternoon and evening until 09z Wed. && .STO WATCHES/WARNINGS/ADVISORIES... None. && $$

529 FXUS65 KMSO 021918 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 118 PM MDT Tue Sep 2 2025 .DISCUSSION... KEY MESSAGES: - Hot and dry conditions through Wednesday with elevated HeatRisk - Increased easterly winds expected Thursday into Friday - Pattern change to showers and thunderstorms begins this weekend The dominant ridge of high pressure will shift slightly westward over the next couple of days, amplifying the ongoing heatwave across the Northern Rockies. This will continue the warming and drying trend through Thursday. High temperatures, combined with warm overnight lows, will continue to elevate HeatRisk to moderate or major levels for the lower valleys of north-central Idaho and northwest Montanaincluding Riggins, Orofino, Thompson Falls, and Libby. The current Heat Advisory for Idaho has been extended through Wednesday evening. As the ridge of high pressure centers just to our west, a period of persistent easterly to northeasterly winds will become a notable change from Thursday into Friday. The increase in east to northeast winds will create choppy conditions on Flathead Lake by Thursday afternoon and evening, with a 25 percent probability of gusts reaching 25 mph between 4 PM and midnight. This wind pattern also has the potential to transport smoke from wildfires burning in Alberta and Saskatchewan southwestward into our region. If you plan to recreate outdoors, keep in mind the potential for increased smoke and choppy conditions on area lakes. Looking ahead to the weekend, forecast models continue to indicate that the ridge will shift eastward, allowing a more southwesterly flow to develop over the region. This will bring a slight cooling trend, though temperatures are expected to remain above average for this time of year. More importantly, this pattern will reintroduce enough moisture and instability to bring a renewed chance for showers and thunderstorms. With precipitable water values ranging from 150% to 200% of normal, combined with light upper-level steering winds, there is a marginal risk for excessive rainfall. Recent burn scars and steep, rocky terrain may be at increased risk for runoff impacts. && .AVIATION...High density altitude and widespread haze will be the primary focuses through Wednesday. MVFR conditions can be expected near local fires, especially during the morning hours for the next 48hrs. Widespread east/northeast winds will develop over the Northern Rockies Thursday. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...Heat Advisory until midnight MDT Wednesday night for Kootenai/Cabinet Region...Lower Clark Fork Region. ID...Heat Advisory until 11 PM PDT Wednesday for Lower Hells Canyon/Salmon River Region...Orofino/Grangeville Region. && $$

322 FXUS65 KBOI 022000 AFDBOI Area Forecast Discussion National Weather Service Boise ID 200 PM MDT Tue Sep 2 2025 .SHORT TERM...Tonight through Thursday night...Slight day-to-day cooling through Thursday but still hot. Limited monsoon moisture moving northward will bring a 10-15 percent chance of showers and high-based late-day thunderstorms to southeast Oregon and southern Owyhee Co/ID through Thursday. Thunderstorms will have gusty outflow winds to 40 mph but minimal rain on the ground until deeper moisture arrives in the long term. Patchy near- surface wildfire smoke will continue in the northern half of the CWA, especially in eastern Valley County/ID. Relatively clear in the southern half. .LONG TERM...Friday through Tuesday...An upper ridge is forecast to remain over the northern Rockies Friday while a shortwave trough approaches the OR and northern CA coast. The dynamics of this trough will interact with the monsoon moisture already in place and bring a 20-40 percent chance of thunderstorms to eastern OR and far southwest ID. A piece of the trough swings inland on Saturday with a chance (30-60%) of showers and thunderstorms across the entire forecast area. Temperatures trend down to near normal by Saturday. Showers and thunderstorms linger Sunday through Tuesday with an upper level low forecast to remain situated near the WA and OR coast. This will keep temperatures generally around normal for the first part of next week. && .AVIATION...VFR. Smoke layers aloft. High density altitude in the afternoons due to heat. Virga and isolated showers/ thunderstorms in southeast OR and near the NV/ID border until 03/04Z. Thunderstorm outflow gusts 30-40 kt. Surface winds: variable 5-15 kt. Winds aloft at 10kft MSL: variable less than 10 kt. KBOI...VFR. Smoke layers aloft. High density altitude in the afternoons due to heat. Surface winds: NW 5-10 kt until 03.02Z, then light and variable. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...None. OR...None. && $$ www.weather.gov/Boise Interact with us via social media: www.facebook.com/NWSBoise www.x.com/NWSBoise SHORT TERM...LC LONG TERM....TL AVIATION.....LC

912 FXUS65 KLKN 022052 AFDLKN Area Forecast Discussion National Weather Service Elko NV 152 PM PDT Tue Sep 2 2025 .KEY MESSAGES... Updated at 151 PM PDT Tue Sep 2 2025 * Cumulus buildups and virga, as well as a few dry thunderstorms across central/northern NV possible today. * Monsoonal moisture continues to build in from the south through the week. * Dry will give way to wet thunderstorms as areal coverage also increases during the week. * Dry conditions return for the weekend as upper flow sifts to the WSW bringing in drier air. && .UPDATE... Issued at 151 PM PDT Tue Sep 2 2025 No updates are planned for this package. && .DISCUSSION... (Today through next Tuesday) Southerly upper level flow look to open a new period of shower and thunderstorm development for the Silver State starting Tuesday afternoon. The pattern is book ended with a broad upper level ridge located over the four corners region, and a upper level trough that is offshore trying to push in over the west coast. This set up will allow for monsoonal moisture to be pulled over the Great Basin from the Gulf of California. Tuesday will see mostly convective build ups and virga, but moisture will be enough for a 10% to 20% chance of a few dry thunderstorms across western and central NV north to the OR/NV border. Wednesday afternoon will see chances increase to 20% to 40% of thunderstorms with a mix of wet and dry storms. Thursday and Friday chances peak at 30% to 70% area wide. There is also a marginal risk of excessive rainfall Thursday and Friday as PW values rise north of one inch, and combined with slow storm motion will create a risk of flooding. Also the only exception to this is far NE Elko county as PW values will range in the 0.6 to 0.75, much lower than the rest of the state, which will keep the risk for dry thunder here. Saturday will see the upper trough lift into Canada as the upper ridge shifts into southern California. This will change the orientation of the upper flow to be out of the West-Southwest. This change will persist into next week leading to much drier conditions especially after Sunday as storm chances end. There is a bit of a disagreement in the upper pattern between the models for next week. The GFS has a strong but dry upper low over eastern Oregon, whereas the EC has strong ridging aloft over Nevada. Either solution favors WSW flow and dry conditions with only potential difference being temperatures. As for temperatures, a cooling trend will be underway as moisture and clouds increase during the week. Highs will start in the mid 80s to mid 90s Tuesday, cooling into the mid 70s to mid 80s by Saturday afternoon. For Sunday through Tuesday Highs will remain in the mid 70s to mid 80s. Overnight lows will not be as cool with clouds on the increase as low range in the low 50 to mid 60s through Sunday morning. Low do cool Monday and Tuesday of next week as lows return to the mid 40s to mid 50s FORECAST CONFIDENCE & DEVIATIONS: There is high confidence in the development of afternoon isolated to scattered to numerous showers and thunderstorms across central and northern Nevada this week. There is high confidence in the change over from dry to wet thunderstorms, with the marginal risk of excessive rainfall by Thursday and Friday. && .AVIATION... VFR conditions forecast to be the primary flight conditions through Wednesday. There is a 10% to 20% chance for dry thunderstorms with VCTS possible for KTPH, KELY between 20Z and 03Z this afternoon. Elsewhere convective buildups will be possible through 03Z with the possibility of virga and gusty winds, but no precipitation. && .FIRE WEATHER... Mid day Tuesday moisture and instability from the trough to the northwest will create isolated dry thunderstorms for fire weather zone 437 and maybe the western portion of zone 438. Better moisture riding southerly flow will create a mix of isolated wet and dry thunderstorms (more dry than wet) for fire zones 424, 425, 426, 427, and 438 through Tuesday evening. Continued southerly flow will make for a similar setup on Wednesday over central Nevada for fire weather zones 424, 425, 426, and 427. Afternoon RH values on Tuesday will near criteria level for all zones, but the increased moisture push from the south will keep RH values well above criteria levels on Wednesday. Strong, gusty winds will not be a factor over the state through Wednesday. && .LKN Watches/Warnings/Advisories... None. && $$ DISCUSSION...86 AVIATION...98 FIRE WEATHER...99