898 FXUS66 KSEW 210325 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 825 PM PDT Mon Jul 20 2026 .UPDATE... Hazy conditions are leading to a picturesque sunset this evening. Currently, most wildfire smoke remains aloft with only localized areas of moderate air quality observed across western Washington. For tonight, dry weather remains in the forecast as high-level cloud coverage streams overhead. Can`t rule out the development of marine stratus overnight but this activity will like remain along the coast. Overnight lows are to range between the mid 50s to lower 60s with urban centers being the warmest. The previous discussion remains below along with an updated marine/aviation section: && .SYNOPSIS... A warming and drying trend will continue across western Washington through the middle of the week, with temperatures reaching the low 90s for many lowland areas Tuesday and Wednesday. Onshore flow will increase during the latter half of the week, bringing cooler temperatures with chances for showers and morning low clouds. && .SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/... An upper level ridge will continue to build over the Great Basin through the middle of the week, with a low pressure system situated offshore. This will maintain southerly flow aloft over western Washington, pulling in warmer air through Wednesday. Temperatures today are on track to peak well into the 80s across much of the lowlands, with further warming bringing temperatures closer to 90 degrees on Tuesday. By Wednesday, many areas east and south of the Puget Sound will see high temperatures peaking in the low to mid 90s, which may result in the warmest day of the year so far. This will also correspond to widespread areas of both Moderate (Orange) and Major (Red) HeatRisk on Tuesday and Wednesday, which reflects an increased risk of heat-related illness to those without access to cooling or hydration. A Heat Advisory remains in effect for all inland lowland areas from Tuesday morning to Wednesday evening. In addition to the heat, northerly flow at times will pull wildfire smoke from British Columbia into Whatcom and Skagit Counties, and an Air Quality Alert has been issued by the Northwest Clean Air Agency. Weak easterly flow tonight into Tuesday will also bring wildfire smoke from eastern Washington west of the crest tonight into Tuesday. While incoming wildfire smoke may cause localized degradations in air quality at times over the mountains, the smoke is not expected to mix down into the lower levels and is favored to stay east of the Seattle metro. && .LONG TERM /THURSDAY THROUGH MONDAY/... The remnants of tropical storm Elida will meander northward late Wednesday into Thursday, and while confidence is low, this may produce isolated thunderstorms over higher elevations. Increased onshore flow by Friday will bring in more seasonable temperatures in the upper 70s to the region, with a return to morning low clouds and afternoon sunbreaks. Models struggle to come into agreement over the potential for any incoming showers in the long term, with ensembles maintaining chances for showers over the northern Olympic Peninsula and northern interior through the weekend and into early next week. 15 && .AVIATION... Southwest flow aloft will continue through Tuesday with a strong upper ridge over the Rockies and weak troughing well offshore. The low level flow is light northerly or weakly offshore. VFR this evening with high clouds. Wildfire smoke aloft across northwest WA may limit both horizontal and slant-range visibility at times into Tuesday. Low LIFR stratus is expected to reach HQM for a short duration early Tuesday morning (mainly between 09-16z). Otherwise VFR conditions elsewhere with high clouds at times. Light winds tonight will increase from the W/NW Tuesday afternoon. KSEA...VFR with high clouds at times. Surface winds light northerly generally below 5 kts through Tuesday morning, becoming NW at 5 to 8 kts Tuesday afternoon. JD && .MARINE... High pressure will remain centered offshore with lower pressure inland through the week. Onshore gradients will ease through the early part of the week as thermally-induced low pressure develops across Western Washington and Oregon. Stronger onshore flow and pushes down the strait look to resume in the latter half of the week as the thermal trough shifts eastward. 27 && .FIRE WEATHER... Elevated fire weather concerns will continue through Wednesday due to very warm and dry conditions. Minimum relative humidities will fall as low as 20% to 30% on Tuesday and Wednesday, with drier locations across the southern Puget Sound potentially bottoming out in the teens. In addition, a thermal trough will build along the coast today and will shift inland during the daytime hours and back along the coast overnight each day through Wednesday. While a large degree of uncertainty remains over the track of incoming showers and thunderstorms, the potential for storms coming in from the south late Wednesday into Thursday pose a risk of elevated fire weather conditions, as additional ignitions from lightning cannot be ruled out. Onshore flow will increase by Friday, bringing cooler temperatures and better overnight RH recoveries through the weekend. 15 && .SEW WATCHES/WARNINGS/ADVISORIES... WA...Air Quality Alert until 9 AM PDT Wednesday for Cascades of Whatcom and Skagit Counties-Foothills and Valleys of the North Cascades-Lowlands of Western Skagit and Northwestern Snohomish Counties-Lowlands of Western Whatcom County. Heat Advisory from 10 AM Tuesday to 11 PM PDT Wednesday for City of Seattle-Downtown Everett / Marysville Area- Eastern Kitsap County-Eastern Strait of Juan de Fuca- Eastside-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- Foothills of the Western and Southern Olympic Peninsula- Lake Crescent Area Including US 101-Lowlands of Lewis and Southern Thurston Counties-Lowlands of Pierce and Southern King Counties-Lowlands of Western Skagit and Northwestern Snohomish Counties-Lowlands of Western Whatcom County-Middle Chehalis River Valley-Northern Hood Canal-Olympia and Southern Puget Sound-Port Townsend Area- Shoreline / Lynnwood / South Everett Area-Southern Hood Canal. PZ...None. && $$

366 FXUS66 KPQR 210500 AFDPQR Area Forecast Discussion National Weather Service Portland OR 1000 PM PDT Mon Jul 20 2026 Updated aviation discussion. && .SYNOPSIS...Ever-changing pattern this week with a warming trend on Tuesday into Wednesday. Higher confidence on Tuesday`s highs being well above normal, but some level of uncertainty lies with Wednesday still as there is another potential weather pattern that would disrupt as significant of heating. Thunderstorms remain possible on Wednesday, especially over the Lane and Linn county Cascades. Cooler with onshore flow starting Thursday. && .SHORT TERM...Now through Wednesday Night...Satellite imagery this afternoon shows widespread cloud cover over the region which has maintained more moderate temperatures throughout the area. Starting to see temperatures rise, but it has been a slow process. Still expecting highs in the mid to upper 80s inland, with cooler temperatures along the Coast, southwest Washington and the Cascades. Tuesday continues to be on track for a significantly warmer day as high pressure builds over the region. This ridge is going to maintain generally clear skies with light winds overnight. Night time temperatures will remain elevated, especially with the aid of cloud cover that fills in overnight. The HREF continues to show a return of southerly flow and cloud cover on Tuesday which, if combined with smoke aloft, could inhibit significant heating. This trend can be observed when comparing models. For example, the NBM is showing around 98 degrees for a high on Tuesday, while the HREF is closer to 95 degrees in Portland. While not a significant drop, it does show that there remains some wiggle room. This is further supported when looking at the probabilities. In Salem for example (also in the Heat Advisory), the temperatures in the 25th to 75th percentile range from 96-100 degrees F. There is a 10% chance that highs could reach around 101 degrees on Tuesday. The Heat Advisory remains in effect through Wednesday. Speaking of Wednesday, that is where conditions become a little be less confident. Ensembles continue to agree on a ridging pattern persisting, but where it ends up is the question. Northwest Oregon and Southwest Washington is sitting right on the outer edge of the ridge which is going to increase southerly to southwesterly flow. In addition, there is moisture in the area from a trough aloft forming off of the coast of California. This trough would disrupt the potential for another significant heating day, and instead bring higher cloud cover and even the potential for rain/thunderstorms. Right now, the trend remains warm, but more and more of the models are showing increasing convection risk. CAPE values over the Cascades are increasing, and looking at forecast soundings, a lot of that instability is aloft. If we maintain lots of cloud cover, the initiation for storms will be limited as the flow aloft is less strong than the last thunderstorm outbreak we experienced. However, if we get the cloud breaks, we could easily see these storms perk up and we could see some elevated thunderstorms. PWATs remain around 1 inch which is a tad lower and would lead towards a dry thunderstorm scenario. Multiple days of above normal heat combined with limited overnight relief will support widespread Moderate HeatRisk across much of the interior. The greatest concern remains centered on the Portland/Vancouver metro, the Columbia River Gorge including Hood River County, and the Kelso/Longview area, where a Heat Advisory is in effect from Tuesday morning through at least Wednesday evening. Within those areas, Major HeatRisk appears increasingly likely Tuesday and Wednesday, especially in locations that see the warmest afternoons and the least nighttime cooling. Those with outdoor plans or without effective cooling should be prepared for elevated heat impacts. So, drink plenty of fluids, stay in a cool place during the heat of the day, stay out of the sunshine, and check up on relatives and neighbors. -27 .LONG TERM...Thursday through Monday...By Thursday and Friday, the ridge is expected to weaken as a broader trough begins to press into the Pacific Northwest. That should allow temperatures to ease a few degrees late in the week, though values may still remain somewhat above average for late July. Beyond Friday, there is currently no strong signal for meaningful precipitation, and temperatures remain mild in the mid 80s. -12 && .AVIATION...Continued VFR flying conditions expected throughout the period at inland terminals with sct/bkn high clouds and unrestricted vis. Nearly calm winds tonight will build to around 5 kt out of the north to northwest by 16-20z Tue. Along the coast, resurgent low marine stratus is again expected, favoring IFR/LIFR conditions through much of the overnight period. LIFR cigs/vis are favored (80% chance of occurrence) at KONP, with chances decreasing to the north; IFR conditions are instead favored (60% chance) at KAST. Slow improvement to MVFR/VFR is expected after 16-18z Tue. Nearly calm winds tonight will build out of the west to northwest at 5-10 kt by 18-21z Tue. KPDX AND APPROACHES...VFR conditions beneath sct/bkn high clouds and light northwest winds are expected. Winds will build slightly to 4-8 kt by Tuesday afternoon. -36 && .MARINE...A typical summertime pattern will continue through the middle of this week with persistent north to northwest winds over the coastal waters. Winds then shift southwest to westerly Thursday into the weekend as weak low pressure develops over the waters. Winds will remain light less than 10-15 kts. Seas will be 3-6 ft at 8-9 seconds through the weekend. -03 && .PQR WATCHES/WARNINGS/ADVISORIES... OR...Heat Advisory from 10 AM Tuesday to 11 PM PDT Wednesday for ORZ108>115-120>122. WA...Heat Advisory from 10 AM Tuesday to 11 PM PDT Wednesday for WAZ204>207-209-210. PZ...None. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland x.com/NWSPortland

056 FXUS66 KMFR 210235 AFDMFR Area Forecast Discussion National Weather Service Medford OR 735 PM PDT Mon Jul 20 2026 ...Updated the Aviation and Marine Sections... .AVIATION...21/00Z TAFs...Areas of LIFR from Cape Blanco northward, including North Bend, and near Brookings are expected to fill in along the entire coast after 04Z this evening then persist through most of Tuesday morning. Patchy LIFR will linger north of Cape Blanco later Tuesday before widespread LIFR returns Tuesday evening. Areas of mid-level and mostly high-level clouds will continue to produce VFR ceilings over portions of northern California and southern Oregon through Tuesday morning. These clouds could produce a few light showers or virga, mainly over Modoc and Lake counties, including Lakeview. By Tuesday afternoon and into Tuesday evening, cumulus buildups are expected with a slight chance of thunderstorms in western and central Siskiyou County, also north and northeastward along the Cascades and across much of south central Oregon. There is a slight chance of wildfire smoke affecting the Medford and Klamath Falls terminals. && .MARINE...Updated 730 PM PDT Monday, July 20, 2026...North winds are gradually subsiding with conditions improving for all areas overnight. Mixed seas then persist Tuesday through Friday with fresh short period northwest swell and also a low longer period south swell due to the remnants of Tropical Storm Elida. Wind wave dominated seas may return during the weekend. && .PREV DISCUSSION... /Issued 135 PM PDT Mon Jul 20 2026/ KEY MESSAGES... * Hazy or smoky conditions will persist for much of SW Oregon south of the Rogue/Umpqua Divide, including Jackson, Klamath, Lake, and Siskiyou counties, with some temporary afternoon into early evening improvement expected as afternoon breezes mix the air near the surface. New fires near the Illinois Valley and the Klamath Basin could add to the smoke in those areas. * Isolated to scattered showers today beneath a canopy of mid and high level cloudiness. Instability is limited, so thunder chances are low - generally 10% or less. Same goes for Tuesday, though odds of thunder are a bit higher 5-15%. The highest risk of thunderstorms for the area will be on Wednesday (could reach scattered coverage Cascades/Foothills eastward), including lesser chances for areas west of the Cascades. * Remaining hot inland during the next week with highs generally 5 to 10 degrees above normal (mid 80s to mid 90s on the east side and lower 90s to 103 for west side valleys). Near or slightly below normal temperatures at the coast will reach the 60s. * A drier pattern takes hold late week, but probably with an increase in afternoon/evening breezes, especially east of the Cascades. DISCUSSION...The main players in our weather pattern this week will be low pressure over the eastern Pacific (including tropical remnants), ridging centered near the Rockies, and a plume of monsoonal moisture wedged in between. This plume of moisture aloft has brought mid and high level clouds into the area today and generating a few light showers. Instability, however, is weak and convection allowing models are suggesting little or no lightning activity. Most precip will evaporate before reaching the ground, but could bring a few hundredths here or there (especially over higher terrain). Showers will diminish this afternoon and evening, and since the mid and high level clouds linger through at least this afternoon, we don`t think we`ll get enough instability for much thunderstorm activity (if any). Models keep thunderstorm probabilities today at generally 10% or less. On Tuesday, a general lack of instability and forcing will keep the convective forecast at a minimum. Even so, we should see at least a thinning of the high cloud cover, so some instability could generate isolated activity, mainly near or just north of Crater Lake in the Cascades and southeastward down to around the Warners during the afternoon/evening. Storm coverage will be isolated at best. Wednesday, stronger southerly flow aloft is expected between the trough offshore tracking northward (including the remnants of Tropical Storm Elida) and the persistent ridge over the Great Basin/Rockies. There is still a modest amount of uncertainty in the convective forecast (especially with areal extent), but there is a decent chance of scattered thunderstorm coverage over a broad portion of our area, to include areas from the Cascades eastward and also portions of the west side (most likely Douglas County east of Roseburg, but also the Siskiyous and western foothills of the Cascades south and east of the Rogue Valley). Farther south and west, coverage should be more isolated or non- existent (coast). Storms do look to trend wetter over time with highest precipitable water values at around 200% of normal (perhaps near or above 1.50 inches). While a widespread severe weather outbreak is not likely, a stronger cell or two could produce strong, gusty winds. Generally, any storms that develop Wednesday will move to the north to northeast, contain frequent lightning, small hail, and gusty winds, and could produce periods of heavy rainfall. The region of greatest instability looks to shift northeastward on Thursday, possibly lingering into northern and/or eastern portions of the east side. For Friday into next weekend, a shift to an onshore flow pattern is likely with a more stable, dry air mass, along with enhanced afternoon and evening winds. -Spilde/BPN FIRE WEATHER...Updated 100 PM PDT Monday, July 20, 2026...A broad moist plume moving south to north today is producing some light showers across the area, with no lightning recorded so far today. With relatively warm air aloft and the high elevation of the moisture creating extensive mid and high level clouds, instability is limited. Some of the radar returns are reaching the ground as light rain showers/sprinkles (especially at higher elevations), but measurable rainfall has been hard to come by. The probability of lightning is not zero, but odds stand at around 5-10%. On Tuesday, there is still an overall lack of instability and forcing, so the chances for showers and thunderstorms remain low. The best chance will be late in the day/evening near the Cascades north of Crater Lake and southeastward along Winter Rim over to the Warner Mtns. This activity looks isolated at best and don`t think any headlines are necessary. By Wednesday, there is a greater concern for increased afternoon and evening thunderstorm coverage. This is due to better instability expected in advance of moisture arriving in southerly flow aloft at peak heating along with the potential for better forcing as the remnants of Tropical Storm Elida push northward offshore. We think the greatest activity in terms of coverage will occur from the Siskiyous and western slopes of the Cascades (FWZ 621, and eastern 622/617) east across the Cascades (FWZ623), and then also east of the Cascades in the typical arc (FWZs 624/625). Isolated storms are also possible elsewhere across the area, including in northern California and across the valleys west of the Cascades. With lightning potential appearing much more abundant Wednesday, a fire weather watch has been issued for the main areas of concern. We should mention that since we`re expecting this air mass to be modified tropical, these storms should become wetter over time, and may even produce periods of heavy rain within their cores. Late in the week (Thursday/Friday), eastward movement in the upper level pattern is likely, which is likely to shift the region of instability east of our area. But, a plausible, slower solution would keep instability and some slight thunderstorm risk over the east side on Thursday. The bigger impact late in the week into next weekend would be the risk of enhanced westerly winds occurring during the afternoons and evenings east of the Cascades along with low humidity. -Spilde/BPN && .MFR WATCHES/WARNINGS/ADVISORIES... OR...Fire Weather Watch from Wednesday morning through Wednesday evening for ORZ617-621>625. CA...PACIFIC COASTAL WATERS...Small Craft Advisory until 8 PM PDT this evening for PZZ356-376. && $$

034 FXUS66 KEKA 202225 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 325 PM PDT Mon Jul 20 2026 .KEY MESSAGES... * Warmer temperatures are bringing minor to moderate HeatRisk through Tuesday. * Slight chance of showers and thunderstorms across the interior through Wednesday with the biggest threat Wednesday afternoon. * Near or slightly below normal temperatures late in the week. .SYNOPSIS...Monsoon moisture is bringing widespread high clouds this afternoon and this is expected to continue through Wednesday. Slightly above normal temperatures continue Tuesday. There is a slight chance for afternoon thunderstorms in the interior Tuesday and Wednesday. Drier weather is expected late in the week with temperatures near or slightly below seasonal normals. && .DISCUSSION...An area of low pressure, the the remnants from Hurricane Elida, is moving up off the California coast. This is bringing moisture with it. Today this is bringing mainly high clouds and a few light showers or sprinkles. There is only minimal, if any instability with this moisture which is limiting the thunder potential. The better dynamics remain off the coast. So don`t really expected any thunderstorms this afternoon, but hard to rule one out. Warmer temperatures are expected again Tuesday with highs in the warmer valleys in the mid to upper 90s. Tuesday late in the afternoon and evening some of the models are showing a small amount of instability, but there really isn`t any forcing to set off a thunderstorm. Still one or two are possible in northern Trinity county in the evening. Wednesday the area of low pressure starts to move past the area and this is expected to bring a little bit of forcing and some instability in the afternoon and evening. This looks like the most likely time for thunderstorms to develop this week. However, if any storms do form they will be moving north and may move into Siskiyou county fairly quickly. Thursday the upper level trough is expected to get closer to the area and this is expected to start bringing cooler temperatures, back to near or slightly below normal with highs in the upper 80s. This is expected to bring some stronger wind west to southwest winds in the afternoon. Similar temperatures and winds are expected to continue on Friday. For details see the fire weather section. High pressure is expected to bring warmer temperatures to the area for the weekend with dry weather. && .AVIATION...Skies have cleared out this afternoon, but stratus remains 5 to 10 miles off the coast. This is expected to move back in this evening, but confidence is low on how quickly it will return. It will likely return around sunset. When clouds do return, models are indicating conditions will quickly drop to LIFR and possibly less than a quarter mile. VFR conditions are expected to return fairly quickly on Tuesday. && .MARINE...Light northerly winds continue on the offshore waters, but closer to the coast winds are light and south to southwest. The steeper are diminishing this afternoon as well. A 3 to 4 foot southerly swell at 12 seconds is moving through the waters along with a 2 foot northwest swell. These conditions are generally expected to continue through much of the week. The swells will fluctuate slightly, but generally remain small. Winds are expected to increase slightly to 10 to 15 kt Tuesday night and early Wednesday before diminishing again to less than 10 kt. Thursday afternoon northwest winds start to pick up once again in the southern waters to around 10 to 15 kt. Winds continue to increase over the weekend. MKK && .FIRE WEATHER...Monsoonal moisture has brought widespread high clouds to the area this afternoon. There is still the potential for a few dry thunderstorms this evening, but the chances are diminishing due to very limited instability. Tuesday There is another chance for thunderstorms, but this looks like a low probability. Some weak ridging pushes over the area keeping the strong inversion at higher levels. Did add a slight chance for northern Trinity county late in the afternoon and evening. Wednesday the upper level low related to the departing tropical system moves closer to the area and increase the potential for some thunder in the afternoon. Confidence remains low on this, but have added thunderstorms to the forecast Wednesday afternoon and evening. Thursday and Friday the threat for thunderstorms diminishes, however some stronger west to southwest winds are expected. At this point it looks like the RH will be too high to warrant a fire weather watch. Will likely add a headline to the forecast once it gets within range of the higher resolution models if the winds remain in the forecast. MKK Afternoon RH continues to be low with most interior areas seeing teens and 20s. High temperates return closer to average early week as high pressure weakens. Winds generally remain light and terrain driven. Monsoonal moisture has arrived and will continue to influence the area through Wednesday. There will be multiple low chances (15% or less) of thunderstorms for the interior areas tonight through Wednesday. Dry low levels will limit precipitation from reaching the ground. && .EKA WATCHES/WARNINGS/ADVISORIES... CA... Red Flag Warning until 6 PM PDT this evening for CAZ403-406- 409>412. NORTHWEST CALIFORNIA COASTAL WATERS... None. && $$ 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

586 FXUS66 KMTR 210446 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 946 PM PDT Mon Jul 20 2026 ...New AVIATION... .KEY MESSAGES... Updated at 154 PM PDT Sun Jul 19 2026 - Approximately 15% chance of high based showers through Tuesday. - Breezy onshore winds return for the second half of the week. - Temperatures will hover around normal through the week. && .SHORT TERM... Issued at 154 PM PDT Mon Jul 20 2026 (This evening through Tuesday night) Afternoon satellite and radar show clouds and showers streaming over the area from post tropical storm Elida. The showers are high based, meaning the bottoms of the the showers are around 5-8000 feet. At this elevation in summer months, the rain coming out of the showers typically evaporated before hitting the ground. Even so, with the forecast cycle, showers were added into much of the area with QPF limited to 0.01", which is generous. Really showers will be lucky to reach a trace. The overall pattern is fairly interesting with a broad ridge over the western US, trying to flex into the west coast, but challenged by trough over the eastern Pacific. This trough is the exit route for post tropical storm Elida, riding up and over the edge of the ridge. This is where the complexities creep in. The strength of the ridge and trough are not static and models are trying to project them, but only offer about a 80% vision rate. Meaning, there is still error in the forecast. The error is showing up in the POP and QPF fields and trying to play with temps as well. As stated, the POP forecast has from NBM and other model guidance for the next 36 hours as Elida passes by. QPF will remain low, unless there is a wobble eastward of the remnant system. Models are showing nice vorticity bands (at 500, 700, and 850 mb) spinning off the remnant low, heading our way on Wednesday. This comes into play as it could provide a focus point for more intense showers, if there remains enough moisture in the area at that time, and right now that does not look probable. This will be something to watch as this system can still make a wobble. At this time there is no expectation of dry thunderstorms or even lightning. The depth of any convection just doesn`t look deep enough to reach the hail growth zone needed to exchange charges and generate lightning. There would need to be a substantial shift in the pattern to find better areas of instability and even then, the system would need to intensify as undergoes extratropical transition, which it is showing no signs of. No mention of dry thunderstorms in the forecast. Models continue to show Tuesday as the warmest day of the week with temps running about 5ish degrees above normal. However, the remnant low may provide more clouds than expected and cap temperatures to around normal. Confidence is high that in the wake of the remnant low temps will cool slightly, around 5ish degrees below normal. By the weekend the four corners high will try to press into the area again causing more warming. Summary: Post tropical storm or remnant low Elida will continue to make the forecast challenging with respect to nearly all sensible weather elements. Keep an eye on an ever changing forecast. && .LONG TERM... Issued at 154 PM PDT Mon Jul 20 2026 (Wednesday through next Sunday) In the wake of the remnant low confidence is high that temps will cool slightly, around 5ish degrees below normal, as troughing prevails. By the weekend the four corners high will try to press into the area again causing more warming. This will take us from a deeper marine layer for the second half of the workweek to a more compressed one for the weekend. The one thing to watch for as the trough makes it self known is onshore winds. Winds from the ocean on to land will increase each afternoon. Some key locations like Petaluma gap, Altamont, and through the Golden Gate will gust each afternoon. Strength will depend on where you are at. && .AVIATION... (06Z TAFS) Issued at 923 PM PDT Mon Jul 20 2026 Mid to high level clouds are interrupting normal radiative process for wides spread stratus. Low confidence that stratus may develop during the overnight through sunrise Tuesday morning. Expecting mainly VFR through the TAF period for majority of the terminals with the exception of KHAF which is on the coastline. Be aware of the potential for elevated showers to produce locally gusty and erratic winds in their vicinity through the forecast period. Vicinity of SFO...VFR expected to prevail through the TAF period with a slight chance of IFR ceilings developing late in the overnight through sunrise Tuesday. Be aware of the potential for elevated showers to produce locally gusty and erratic winds in their vicinity through the forecast period. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...VFR is expected to prevail with a slight chance of IFR ceilings developing overnight before sunrise or shortly after. If ceilings don`t develop, expect VFR through the remainder of the forecast period. Be aware of the potential for elevated showers to produce locally gusty and erratic winds in their vicinity through the forecast period. && .MARINE... (Today through Saturday) Issued at 1049 AM PDT Mon Jul 20 2026 Light to locally moderate northwesterly winds will prevail through midweek, becoming moderate Thursday into Friday. Slight to moderate seas will prevail. Tropical cyclone activity in the Eastern Pacific Ocean will spur several rounds of moderate period southerly swells; hazardous conditions from mixed seas may result. Instability from the remnants of the tropical cyclone will also bring a slight chance of convection that may bring showers as well as gusty and erratic outflow winds that would be result in hazardous conditions to small craft. && .FIRE WEATHER... Issued at 154 PM PDT Mon Jul 19 2026 No significant impacts expected as sub-tropical moisture moves over the Bay Area and Central Coast. There has been some discussion of dry thunderstorms, but as of this afternoon models are not indicating an environment that would support their development. At this point I would give dry thunderstorms a probability of less than 1% this week. What should be expected is an isolated shower here or there with little to no accumulation. The marine layer will remain fairly well mixed out through Tuesday afternoon, but should start to build back in late Tuesday and Tuesday night. Expect it to reach around 1000 feet by midweek. Strong onshore winds will develop each afternoon for the second half of the week. They typical places will gusts like they do every summer afternoon. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...None. && $$ SHORT TERM...BFG LONG TERM....BFG AVIATION...JM MARINE...JM 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

457 FXUS66 KOTX 210509 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 1009 PM PDT Mon Jul 20 2026 .KEY MESSAGES... - Warming trend through midweek with temperatures pushing upper 90s to near 100 by Tuesday. Widespread moderate and major HeatRisk. - Critical fire weather conditions likely Thursday through Saturday isolated to scattered thunderstorms followed by dry and breezy winds && .SYNOPSIS... Dry weather with occasionally breezy winds will prevail through at least midweek. Temperatures will trend warmer in this timeframe with high confidence for widespread moderate and major HeatRisk Tuesday through Thursday. Increasing moisture in the mid to late week timeframe may bring an elevated threat of thunderstorms. Dry and breezy winds Friday and Saturday will result in elevated to critical fire weather conditions. && .DISCUSSION... Today through Wednesday: Primary focus through Wednesday continues to be on the expected heat, as well as potential impacts from regional wildfire smoke. The Inland Northwest will remain under the influence of a strong high pressure ridge extending across the Intermountain West from the south-central Plains. A weakening shortwave will track from east-central British Columbia this afternoon to central Alberta by Tuesday morning. This trough will induce a light northerly flow under 15kts across southwestern BC/Alberta and into northern Washington. BUFKIT profiles over eastern WA indicate light, variable flow through about 600-500mb until later Wednesday. This will allow the overhead smoke and haze mainly from the Kaiser Canyon and Modrite fires to linger over the region today through at least Tuesday. During periods of deeper mixing in the afternoon this may bring an increase to surface-level smoke in the Spokane area, though the highest smoke concentrations will likely be closer to the wildfires themselves. Wildfire smoke monitoring via satellite will be challenging to impossible with the abundant mid/high cloud cover overhead as upper level monsoonal moisture advects into the region. Not out of the question that a few light showers/sprinkles occur in the vicinity of the WA/ID Palouse or to the south across the Blues. The aforementioned ridge will also bring an increasingly hot airmass to the Inland Northwest through midweek, with 850mb temperatures peaking around +28C to +29C by Wednesday afternoon. This will translate to daytime high temperatures in the mid 90s to low triple digits Tuesday through Thursday, with Wednesday likely being the hottest day of the week. There remains uncertainty in max temperatures in this timeframe due to potential cloud cover and wildfire smoke. NBM 25th percentile advertises highs well into the mid 90s Tuesday and near 100 Wednesday, though if wildfire smoke is thicker than anticipated in any one location it could prevent the higher end temps from being realized. Have issued Heat Advisories with this update for both Tuesday and Wednesday, though Tuesday`s temperatures will be marginal across much of eastern WA and north ID compared to Wednesday. Ensemble spread in temperatures notably increases by Thursday likely due to the higher potential for cloud cover. Thursday through Sunday: Confidence continues to increase in fire weather conditions deteriorating moving later into the week as the strong monsoonal ridge to the east begins to break down. A deep longwave trough pivoting southeast from Alaska will phase with a stationary secondary trough off the Pacific coast. This aggregate trough then weaken as it gradually slides into the Inland Northwest over the weekend. Synoptic moisture will remain elevated Thursday into early Friday with the EC ensemble indicating PWAT anomalies of 125% to 180% in this timeframe, highest across the ridges of the Cascades and Blue Mountains. A strengthening 80-90kt 250mb jet rounding the base of the offshore trough will place portions of the Inland Northwest into the favorable zone for added lift under the left exit region. This may set the stage for one or multiple rounds of scattered convection centered on Thursday, potentially as early as Wednesday night and lingering into Friday morning. The finer details remain a bit murky at this range though cannot rule out a combination of wet and dry thunderstorms, with highest chances across the mountains where greater upslope lift will be present. This is particularly concerning not only due to already higher than average wildfire activity in the region, but because the trough sliding through will likely push a dry cold front into the region between Friday and Saturday. Long range ensembles are in fairly good agreement in this resulting in at least a couple of days of dry and breezy conditions, with the NBM forecasting sustained winds over 20 mph and gusts to 30-35 mph east of the Cascades. In all this is shaping up to be a situation where Red Flag Warnings may be initially needed to cover the lightning threat Thursday, with windy/low RH RFWs for Friday/Saturday. Will need to continue monitoring this setup and consider Fire Weather Watches with future updates. On the plus side, the front should also bring some relief from the hot temperatures seen earlier in the week, though remaining seasonably warm/hot with daytime temps in the upper 80s and low 90s. /PMP/SGK && .AVIATION... 06Z TAFS: Primarily VFR conditions will prevail over the next 24 hours. Light winds will allow for smoke from local wildfires to accumulate near the surface, resulting in periods of MVFR visibilities around KGEG/KSFF, and maybe MVFR/IFR at KMWH. Additionally, mid and high cloud cover will continue to stream overhead into Tuesday as monsoonal moisture aloft increases. FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: Low confidence in exact reduction in visibilities from wildfire smoke at the TAF sites. ----------------------- Confidence descriptors: Low - Less than a 30 percent chance Moderate - 30 to 70 percent chance High - Greater than a 70 percent chance For additional probabilistic information for NWS Spokane airports, please refer to the Aviation Dashboard on our webpage: https:/www.weather.gov/otx/avndashboard && .Preliminary Point Temps/PoPs... Spokane 90 64 95 64 99 66 / 0 0 0 0 0 0 Coeur d`Alene 91 66 95 66 98 67 / 0 0 0 0 0 0 Pullman 88 57 92 59 94 60 / 0 0 0 0 0 0 Lewiston 94 67 100 69 102 70 / 0 0 0 0 0 10 Colville 92 59 96 59 99 62 / 0 0 0 0 0 0 Sandpoint 88 61 92 61 96 64 / 0 0 0 0 0 0 Kellogg 88 62 92 62 94 63 / 0 0 0 0 0 0 Moses Lake 94 64 99 66 101 68 / 0 0 0 0 0 0 Wenatchee 92 71 99 74 102 76 / 0 0 0 0 0 0 Omak 94 68 99 70 102 72 / 0 0 0 0 0 0 && .OTX WATCHES/WARNINGS/ADVISORIES... WA...Air Quality Alert until 9 AM PDT Tuesday for Northeast Mountains-Spokane Area-Washington Palouse. ID...Air Quality Alert until noon PDT today for Central Panhandle Mountains-Coeur d`Alene Area-Idaho Palouse-Lewis and Southern Nez Perce Counties-Lewiston Area-Northern Panhandle. && $$

317 FXUS66 KPDT 210525 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 1025 PM PDT Mon Jul 20 2026 .KEY MESSAGES... 1. Continued dry and warm conditions through the week *Excessive Heat Watch in Effect* 2. Isolated to scattered thunderstorms Wednesday and Thursday 3. Hot, dry and windy conditions return Friday && .DISCUSSION... Current radar is showing a few echos across the central portion of the region. Ground observations show mostly a trace with a few isolated locations in central OR showing 0.02-0.03 inches of rain. Satellite shows clouds over much of the region with heavy smoke near the surface. The smoke has kept the temperatures across the region 5- 7 degrees below the original forecast. Temperatures are sitting in the upper 70s instead of the mid 80s. Models show the upper level ridge to remain overhead through Thursday keeping the region under dry and warm conditions. Temperatures will steadily increase and there is 70-80% chance of seeing major HeatRisk Tuesday through Thursday with highest probabilities being Wednesday. If the smoke lifts, NBM shows temperatures to reach between 100-105 in the Columbia Basin ands the Gorge with isolated areas along the foothills seeing upper 90s to 100 degrees. That coupled with the high overnight temperatures in the upper 60s to low 70s will cause heat related impacts to occur. Confidence in the HeatRisk is high (70-90%). By Wednesday, models are in decent agreement and show a slight pattern shift with the upper level ridge shifting towards the Four Corners and advecting some monsoonal moisture up into the region. Clusters show the main difference to be mainly with the amplitude of the ridge. NBM raw ensembles show Wednesday to have 40% chance of thunderstorms through Deschutes and Grant counties after 2 PM. Looking at soundings show CAPE values over 400-500 J/kg, lapse rates 9-10 C/km, effective bulk shear of 25-30 kts and LIs of -4 and PWATs of 0.05-1.0 inches. NBM QPF continues to show these storms to be more on the drier side with less than 10% chance of a wetting rain. Cannot rule out isolated dry thunderstorms mixed with wet thunderstorms and with the fuels as ready as they are, not a lot is needed to ignite a fire. This pattern is similar to the pattern from last week and therefore a Red Flag Warning has been issued for abundant lightning over central OR and the eastern mountains 11 AM Wednesday to 11 PM Wednesday. Thursday models show a dry upper level low beginning to push into the region shifting the upper level high of to the east. In house calculations show the pressure gradients along the Cascades tightening which will bring elevated winds to the Cascade Gaps as well as portions of the southern Blues and central OR. NBM raw ensembles shows the region with the highest probabilities for 20 mph sustained winds is through the Gorge and foothills of the southern Blues at 70-90%. 15 mph sustained winds expected through the Kittitas Valley and through portions of central OR with 60-80% probabilities. With the continued dry and warm conditions, relative humidities will remain low and coupled with the winds elevated fire weather concerns for Friday and Saturday. && .AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/... VFR conditions generally expected through Tuesday, with winds 10 kts or less. However, smoke from area wildfires could cause MVFR or even lower conditions at almost any site through the period. && .FIRE WEATHER... There are two periods of concern for fire weather. The first is with the potential for thunderstorms on Wednesday through central OR and the eastern mountains. There is a 10-30% chance of isolated to scattered thunderstorms through the aforementioned portion of the CWA. These thunderstorms are expected to bring gusty outflow winds of 25-35 mph as well as abundant lightning. With that, a Red Flag Warning has been issued for OR zones 698, 700 and 705. && .Preliminary Point Temps/PoPs... PDT 62 96 66 99 / 0 0 0 0 ALW 67 98 71 101 / 10 0 0 0 PSC 65 100 68 103 / 0 0 0 0 YKM 68 99 70 103 / 0 0 0 0 HRI 66 99 70 103 / 0 0 0 0 ELN 65 97 68 101 / 0 0 0 0 RDM 58 94 62 96 / 0 0 10 20 LGD 62 97 67 99 / 0 0 0 0 GCD 59 96 64 96 / 0 0 10 10 DLS 69 101 73 104 / 0 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... WA...Heat Advisory from 11 AM Tuesday to 9 PM PDT Thursday for WAZ024-027>029. Air Quality Alert until 9 AM PDT Wednesday for WAZ028>030. OR...Heat Advisory from 11 AM Tuesday to 9 PM PDT Thursday for ORZ041-044-507. Air Quality Alert until 4 PM PDT Wednesday for ORZ044-049-050- 502-503-505>509-511. Red Flag Warning from 11 AM to 11 PM PDT Wednesday for ORZ698- 700-705. && $$ DISCUSSION...90 AVIATION...77 FIRE WEATHER...82

961 FXUS65 KREV 202117 AFDREV Area Forecast Discussion National Weather Service Reno NV 217 PM PDT Mon Jul 20 2026 .KEY MESSAGES... * Afternoon shower and thunderstorm chances each day through midweek, with a drier pattern more likely returning by late week. * Abundant moisture and slower storm motions will introduce flash flooding potential from heavy rainfall as the main concern today and Tuesday. * Typical July warmth, breezy afternoons and drier conditions may produce elevated fire weather conditions at times later this week and into the weekend. && .DISCUSSION... Today: * Convection is developing near Lee Vining and Bridgeport within today`s favored corridor from Mono County north through the Walker, Smith, and Mason Valleys into Mineral and southern Lyon Counties. Showers and thunderstorms have a 30-50% chance south of I-80 and east of US-395, with peak coverage from noon-7 PM and activity possibly lasting through 11 PM. NBM 12-hour thunder probabilities range from 30-35% across Mono and Mineral Counties and 20-25% across southern Lyon County, decreasing to 10-20% around Tahoe, Carson City, and Reno. PWATs of 0.9-1.3 inches are around 160-200% of normal. Forecast soundings show midlevel RH of 85-95%, locally 1000-1200 J/kg of MUCAPE, freezing levels near 15-17 kft MSL, and warm-cloud depths around 1.5-2.5 km in the more humid profiles. This supports efficient warm-rain processes and locally intense rain rates. NBM areal-average QPF through Tuesday morning is generally only a few hundredths to a few tenths, but embedded convective maxima approach one inch. HREF/REFS members produce localized multi-inch totals, highlighting the difference between areal-average QPF and rainfall beneath an individual storm. Corfidi vectors of 15-20 kt indicate greater storm translation than expected Tuesday, although terrain anchoring and redevelopment along intersecting outflows could still produce repeated heavy rain. Isolated outflow gusts of 50+ mph and small hail are secondary concerns. Showers may linger overnight, with around a 5-10% chance of lightning. Tuesday & Wednesday: * Moisture peaks Tuesday, with PWATs of 0.9-1.3 inches, or roughly 200-250% of normal. The favored heavy rain corridor expands from Mono, Mineral, and southern Lyon counties northwest through the Carson Valley and eastern Tahoe slopes into the Virginia Range and Truckee Meadows. NBM 12-hour thunder probabilities increase to 40-50% across Mono, Mineral, and southern Lyon Counties, 35-45% around Carson Valley, and 30-40% across Tahoe and Reno- Sparks. Breaks in the cloud cover and western NV valley highs well into the 90s should support roughly 500-1500 J/kg of MUCAPE. Forecast soundings also maintain deep midlevel moisture and freezing levels near 16 kft MSL. Corfidi propagation vectors weaken to 7-10 kt, increasing the potential for slow-moving clusters and repeated development over similar areas. Given the broader coverage, anomalous moisture, and slower propagation, a second Flood Watch has been issued from noon-11 PM Tuesday. This includes today`s watch area and expands north into the Tahoe Basin and Reno-Carson City-Minden corridor. * Thunderstorms remain possible Wednesday, primarily south of I-80. NBM 12-hour thunder probabilities are around 20-25% near Reno, Carson City, and Tahoe and 30-35% near Bridgeport, Hawthorne, and Mammoth Lakes. Coverage will be lower than Tuesday, while faster storm motions should reduce the duration of heavy rainfall over any one location. Localized flooding remains possible where repeated rainfall occurs during the preceding two days. Convection diminishes Wednesday evening, with most areas dry by 12Z Thursday. Thursday through Monday: * Monsoonal moisture begins shifting east Thursday, with 12-hour thunder probabilities decreasing to around 5-15% across western Nevada and the eastern Sierra. Similar probabilities continue Friday through Monday, generally remaining below 10% north of I-80 and locally reaching 15-20% near southern Mono County over the weekend. Thus, an isolated storm cannot be ruled out near Mono County or the Nevada Basin and Range, but widespread convection is unlikely. Increasing afternoon west winds are possible Thursday and Friday as drier air arrives. Otherwise, warm and mainly dry conditions are favored through Monday, with western Nevada valley highs in the 90s and locally near 100 degrees. -Johnston && .AVIATION... * VFR will prevail outside convection through 22/18Z. Thunder probabilities today are around 30-35% near KMMH and 10-20% near the Tahoe and western Nevada terminals. Tuesday probabilities increase to 40-50% near KMMH and 30-40% near KTVL, KTRK, KCXP, and KRNO. Direct impacts could produce brief MVFR/IFR visibility, mountain obscuration, small hail, and erratic outflow gusts approaching 40 kt. Activity should diminish after 06Z Wednesday. * KRNO: West winds increase gusting to 25 kt from 23-04Z, then decrease from the northwest overnight. There is a 30% chance of -SHRA from 00-10Z, with VCSH from 04-10Z. Ceilings near 9 kft and VFR visibility are expected. The 12-hour probability of thunder increases to around 35% Tuesday afternoon and evening, with abrupt wind shifts and brief visibility reductions possible near storms. -Johnston && .HYDROLOGY... * A Flood Watch remains in effect from 2-11 PM today for Mono County and Mineral/southern Lyon Counties. A second Flood Watch has been issued from noon-11 PM Tuesday for those areas plus the Tahoe Basin and Reno-Carson City-Minden corridor. WPC maintains a Marginal Risk (at least 5%) for excessive rainfall across southern portions of the region today, expanding north across western Nevada and the Tahoe Basin Tuesday. Today`s primary flash flood corridor extends from Mono County through the Walker, Smith, and Mason Valleys into Mineral and southern Lyon Counties. Tuesday`s corridor expands north into the Carson Valley, eastern Tahoe slopes, Virginia Range, and Reno-Sparks area. Individual storm tracks remain uncertain, but repeated development could produce flash flooding near steep terrain, burn scars, normally dry channels, and urban areas. Clear drains where possible to limit urban ponding. Area rivers and streams could see rapid rises and increased sediment loads with localized heavy rain, but no river flooding is expected. -Bardsley/Johnston && .REV Watches/Warnings/Advisories... NV...Flood Watch from Tuesday afternoon through Tuesday evening NVZ001>003. Flood Watch until 11 PM PDT this evening NVZ001. CA...Flood Watch from Tuesday afternoon through Tuesday evening CAZ072-073. Flood Watch until 11 PM PDT this evening CAZ073. && $$

294 FXUS66 KSTO 201930 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 1230 PM PDT Mon Jul 20 2026 For additional details on weather and expected impacts over the next 7 days, please visit weather.gov/sto/briefing. .KEY MESSAGES... - Monsoonal and subtropical moisture pushing through the area next few days, mainly bringing sprinkles or a stray shower to Valley; slight chances for higher elevation thunderstorms. - Seasonable high temperatures continue, Minor HeatRisk with areas of Moderate HeatRisk through Wednesday, then widespread Minor HeatRisk into the weekend. - Elevated fire weather conditions due to dry/wet thunderstorms chances in the higher elevations today through Wednesday. && .DISCUSSION... Mid-level to high clouds passing through the area this afternoon, as subtropical moisture is pushing towards California from Post-Tropical Cyclone Elida. A few sprinkles/light showers have been observed at lower elevations through the morning, however nothing significant has reached the ground. We will continue to have scattered cloud coverage in the Valley throughout the rest of the day, while in the Sierra monsoonal moisture associated with a high pressure in the Rockies moves in. While the NBM has roughly 10-20% chances for an afternoon shower or dry/wet thunderstorm this afternoon, primary limiting factor will once again be the lack of instability. Forecast soundings in higher elevations do not reveal much in the form of MUCAPE or elevated instability in our CWA. Better instability and vorticity/forcing will reside along and east of the Sierra crest. Similar conditions expected tomorrow however better thunderstorm chances in the Sierra are expected. Slightly stronger push of monsoonal moisture coupled with ridge-riding shortwaves may help provide additional instability to produce thunderstorms in the afternoon and evening hours. As such, with the threat of lightning from any storm that develops, elevated fire weather conditions will continue through Wednesday mainly from the risk of new fire starts from lightning outside of rain cores. Our precipitation chances will begin to back off Thursday as off shore troughing takes over the synoptic setup and the ridge in the rockies begins to dig further south into the Four Corners region with drier air embedded limiting convection potential for our CWA. Temperature wise, we continue to be mostly seasonable for the next few days, with mostly Minor HeatRisk and areas of Moderate HeatRisk in the Valley. Warmest day in the short-term forecast is Wednesday, where triple-digit heat is expected in the northern Sacramento Valley and mid to upper 90s for the rest of the Valley. "Cooler" temperatures Thursday and Friday, then a return to mid 90s and triple-digits expected. && .AVIATION... VFR conditions next 24 hours across interior NorCal TAF sites. SCT to BKN clouds across the Delta and Sacramento areas. Surface winds below 12 knots except in Delta vicinity where gusts of 25 to 30 knots possible through around 06z Tuesday. Slight thunderstorm chances in higher elevations from 20z through 07z. && .STO WATCHES/WARNINGS/ADVISORIES... None. && $$

562 FXUS65 KMSO 201844 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 1244 PM MDT Mon Jul 20 2026 .DISCUSSION... KEY MESSAGES: - Periods of haze and smoke persist across the region into tonight. Low rain shower and storm chances. - Monsoon moisture surge returns Tuesday through Thursday. Localized flash flooding and a few severe thunderstorms possible. - Hot temperatures are expected this week, with highs reaching the 90s up to 106 degrees in the lower elevations of Idaho. This afternoon through Wednesday...Upper level monsoonal moisture will continue to stream across the Northern Rockies into Tuesday morning, bringing persistent high and mid-level cloud cover and isolated light showers. Smoke and haze from wildfires in Oregon and Washington will intermittently degrade air quality, though a developing easterly pressure gradient tonight may offer some localized clearing. Atmospheric moisture deepens significantly on Tuesday, with precipitable water (PWAT) values climbing to 200-250% of normal for the region. However, abundant morning cloud cover will likely limit surface instability and overall thunderstorm potential. By Tuesday afternoon, high-resolution guidance indicates scattered thunderstorm development from Lemhi County into Southwest Montana, where brief heavy rainfall and erratic wind gusts exceeding 40 mph will be the primary threats. By Wednesday afternoon, the threat shifts slightly northward. Areas south of U.S. Highway 12 will see an increased risk of locally heavy rainfall capable of triggering debris flows or flash flooding. The overall magnitude of this threat remains highly conditional on morning clearing and the resulting realized instability. It will also be quite warm to hot. NBM temperatures are on the warmer side compared to most guidance and would bring temperatures near heat advisory levels to the lower elevations of north-central Idaho. However, there is considerable uncertainty regarding how much clouds and smoke may impact the high temperature forecast. Still advisories may be needed for the Wednesday/Thursday time period if confidence increases. Thursday through the Weekend...Thursday presents a more dynamic setup as the region transitions from deep monsoonal moisture to a drier, more sheared southwesterly flow. This combination of enhanced vertical wind shear and increased instability could support strong to severe thunderstorms, making Thursday a key period to monitor. By Friday and into the weekend, the synoptic pattern shifts toward near-critical fire weather conditions. Increasing westerly winds, a drying air mass, and a sharp decline in shower activity will combine to elevate fire danger across the region. && .AVIATION...VFR conditions will prevail through Tuesday morning. Monsoonal moisture overspreading the region will maintain widespread high and mid- level cloud cover and isolated light showers. By Tuesday afternoon, scattered thunderstorms are possible across Lemhi County and Southwest Montana; however, convective development remains highly conditional on the clearing of morning cloud cover. If these storms materialize, brief MVFR ceilings and visibilities may impact KSMN and KBTM after 21/2200Z. Winds will remain relatively light and diurnally driven through this afternoon. An easterly pressure gradient will develop across western Montana tonight into Tuesday morning, but peak gusts are expected to remain under 20 knots. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...None. ID...None. && $$

301 FXUS65 KBOI 210550 AFDBOI Area Forecast Discussion National Weather Service Boise ID 1150 PM MDT Mon Jul 20 2026 .UPDATE...Updated aviation discussion. && .KEY MESSAGES... - Hot temperatures this week, hottest today with a Heat Advisory in the Snake Plain and high desert. - Isolated to scattered showers and thunderstorms near the Idaho/Nevada border today. - Showers/thunderstorms increase through midweek with heavy rainfall possible especially on Wednesday. - Areas of smoke through the week. && .SHORT TERM /Through Wednesday Night/... Issued 225 PM MDT MON JUL 20 2026 The central U.S. upper-level ridge will continue to build northwest across the Great Basin today, causing the hottest temperatures across the region through the short term period. Highs will reach the upper 90s to 105 degrees in the lower valleys, and a Heat Advisory remains in effect for much of the lower elevations across the Snake Plain and high desert until 9 pm MDT tonight. Southerly flow aloft will continue to transport monsoonal moisture into the region, with widespread PWAT values above the 95th percentile (over 1.00") today. Isolated to scattered showers and thunderstorms will develop near the Idaho/Nevada border this afternoon and evening, with outflow wind gusts to 40 mph possible. Outside of storms, breezy conditions will develop late today with gusts 15-30 mph, locally up to 40 mph in eastern Oregon this evening. Overnight, remnants from these thunderstorms are expected to move north across SW Idaho as weak showers that are mostly virga. There is a 10-15% chance that these intensify to thunderstorms as they move over the lower Snake Plain overnight around 2 a.m. MDT and further into the Boise Mountains. On Tuesday, shower and thunderstorm potential will expand across higher elevations, especially the west-central Idaho mountains and ID/NV border. PWATs increasing further Tuesday as well, with widespread values near the 97th percentile (near 1.15"). Continued monsoonal moisture streaming in will also create light rain / virga showers over SE Oregon, with minimal QPF. Temperatures will be a few degrees cooler than Monday. By Wednesday, precipitable water values will rise to around 1.25 inches, near the 99th percentile. An embedded shortwave trough will interact with this moisture, increasing shower and thunderstorm coverage, especially across eastern areas where precipitation chances will reach 30-70%. The higher terrain across southeast Oregon and far southwest Idaho will see a 20-40% chance of precipitation with a less than 20% chance in the lower valleys. With deep moisture in place and slow expected storm motion, thunderstorms will be capable of heavy rain and flash flooding, especially over burn scars and steep terrain. Current long-range forecast models have QPF bullseyes of near 0.5" in a 3 hour period, which is quite intense. With convective allowing models coming into range tomorrow, the threat timing and intensity will become clearer, however the concern level is already high. Temperatures will be similar to that on Tuesday. With southerly flow aloft, smoke should improve each afternoon, but northwest surface winds are expected to continually transport the smoke back into SE Oregon and SW Idaho. && .LONG TERM /Thursday through Monday/... Issued 225 PM MDT MON JUL 20 2026 Drier Thursday as upper flow changes from SSW to WSW and shifts the monsoon flow eastward and out of our CWA. The main upper high over the interior western US will also expand westward out into the Pacific effectively preventing more monsoon moisture from reaching our area. On Monday an upper trough off the northwest coast will come inland across WA and northern OR beginning a breezy and cooler period in our CWA. && .AVIATION /06Z Tuesday through Wednesday/... Issued 1146 PM MDT MON JUL 20 2026 Generally VFR. Areas of MVFR-IFR visibility due to wildfire smoke. Isolated/scattered showers will spread north through morning and afternoon. Thunderstorms re-develop near NV-ID border in the afternoon, with brief heavy rain and outflows to 40 kt. High density altitude during afternoon heat. Surface winds: generally SW-NW 5-15 kt with localized gusts around 25 kt. Winds aloft at 10kft MSL: variable 5-10 kt. KBOI...Generally VFR. Potential for MVFR visibility in the early morning hours due to wildfire smoke. A 15% chance of light rain after Tue/09Z. High density altitude during afternoon heat. Surface winds: variable around 6 kt through morning, then NW 10-15 kt with gusts 20-25 kt in the afternoon. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...Air Quality Alert until 3 PM MDT Wednesday for IDZ011-012-014- 033. OR...Air Quality Alert until 1 PM MDT /noon PDT/ Wednesday for ORZ061>064. && $$ www.weather.gov/Boise Interact with us via social media: www.facebook.com/NWSBoise www.x.com/NWSBoise AVIATION.....SH SHORT TERM...CH LONG TERM....LC

385 FXUS65 KLKN 210314 AFDLKN Area Forecast Discussion National Weather Service Elko NV 814 PM PDT Mon Jul 20 2026 .KEY MESSAGES... * Historically high atmospheric moisture content Tuesday * Flash Flood Watch Tuesday for most of Northern and Central Nevada * A few strong thunderstorms possible in most of Northern and Central Nevada each afternoon and evening today through at least Wednesday && .DISCUSSION... (Tonight through next Monday) 8:00 PM Update. The Heat Advisory which was in effect for portions of Northern Nevada has expired. Temperatures have cooled significantly across most of the region this evening, largely due to thunderstorm activity. Storms did not reach Humboldt County this evening (where current temperatures remain in the upper 80s to low 90s as of 8PM), however temperatures there and across the region will continue to cool the rest of this evening and overnight. High temperatures Tuesday will be 3 to 5 degrees cooler than the highs reached Monday. No changes to the forecast at this time. && .AVIATION... VFR conditions will prevail at all terminals through at least the next 24 hours. Showers/thunderstorms are expected in the vicinity of KEKO, KELY, KTPH, KBAM, and KWMC this afternoon into this evening. Direct terminal impact cannot be ruled out. The strongest thunderstorms could produce erratic wind gusts near 45 knots and reduced visibility in heavy rainfall. && .FIRE WEATHER... A few strong thunderstorms are possible each afternoon and evening for the next few days. The primary hazards will be small hail, wind gusts near 55 mph, and cloud to ground lightning strikes. Enhanced runoff and localized flooding is possible in storms that form over areas with antecedent rainfall from earlier this week (especially portions of 470 and 425). && .LKN Watches/Warnings/Advisories... Flood Watch from Tuesday morning through Tuesday evening NVZ031-033>041. && $$ DISCUSSION...96 AVIATION...84 FIRE WEATHER...84