511 FXUS66 KSEW 181609 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 909 AM PDT Mon May 18 2026 .SYNOPSIS... High pressure will remain situated offshore through much of next week, maintaining near-normal temperatures across western Washington with cloudy mornings and sunshine in the afternoons. A few weak systems will move over the top of the ridge towards the middle of next week, bringing little more than a few periods of sprinkles. && .SHORT TERM /TODAY THROUGH WEDNESDAY/... Upper-troughing currently over the Great Basin while an upper- level ridge is just offshore the PNW. High clouds are currently streaming in under northwest flow aloft. Stratus has been confined to west central Washington between the Kitsap Peninsula and into the South Sound with the edges beginning to erode away. This will give way to mainly just high clouds and some fair weather cumulus across the area this afternoon. High temperatures are forecast in the 60s across the interior with 50s along the coast. Increasing onshore flow will lead to breezy winds through the Strait of Juan de Fuca this evening with gusts up to 30 mph on Whidbey Island before gradually decreasing later tonight. HREF suggests a 35% chance of gusts exceeding 35 mph. Overnight lows will fall into the 40s. Upper-ridging is likely to maintain through midweek as conditions remain rather benign. Weak disturbances will attempt to traverse along the periphery of the ridge - maintaining slight (15% or less) PoPs but mostly for the mountains. Temperatures are to remain near-seasonal throughout this period with highs in the 60s to near lower 70s and lows in the 40s. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... The upper level ridge offshore will begin to flatten on Thursday as a low pressure system slowly strengthens and lowers from the Gulf of Alaska. Conditions are favored to remain dry into the first half of the weekend as zonal flow sets up aloft, with continued mild temperatures. Ensembles are honing in on a potential pattern change by the end of next weekend, with increasing chances for widespread rainfall arriving Sunday evening. However, the details remain uncertain at this time. 41 && .AVIATION... North/northwesterly winds will persist aloft as an upper level ridge remains nudged over the region. Onshore flow will continue in the low levels, which allowed for some localized stratus to push inland this morning, mainly for areas along the coast, the Southwest Interior, and the south Sound where these terminals are seeing MVFR/IFR conditions likely through 18z (most likely for KHQM, KPWT, and KOLM). Expect cigs at the remainder of the terminals to remain VFR through the day. Winds remain light southerly at 6 kt or less across the majority of the interior terminals this morning, outside of KPAE, where winds continue out of the north. Winds along the coast are light northwesterly and KCLM remains westerly between 8-12 kt under increased onshore flow. Winds will increase to 7-10 kt this afternoon and look to switch to the north across the interior between 00-03Z tonight. A weak, splitting frontal system will move into the area tonight into Tuesday, with the main impact being more widespread stratus by Tuesday morning. KSEA...MVFR ceilings this morning with broken clouds at the terminal around 1500 to 2000 ft. Ceilings will rebound to VFR likely after 17z and will remain VFR throughout the day. A much greater probability (40-45 percent) exists of ceilings dropping to MVFR by Tuesday morning. Winds are southerly and will increase to 7-10 kt this afternoon, before switching to the north between 00-03Z. 14/Mazurkiewicz && .MARINE... High pressure will remain situated over the northeastern Pacific through much week, bringing a prolonged period of north/northwesterly winds to the coastal waters. A weak, splitting frontal system will move into the waters tonight into Tuesday and will bring an increase of onshore flow along the central and eastern Strait of Juan de Fuca, with another round of small craft westerlies expected this afternoon and evening. High pressure will build back into the coastal waters in the wake of the front. Onshore flow will persist throughout much of the week and will result in daily pushes of westerly winds along the Strait. The next weak frontal system looks to move into the area waters Thursday into Friday, followed by another late next weekend. Seas will generally hover between 6-8 ft through the first half of the week, before increasing towards 8-10 ft mid to late week. The latest GEFS probabilistic guidance is highlighting roughly a 20-40 percent chance of seas exceeding 9 ft by next weekend. 14 && .HYDROLOGY... The daily hydrology discussion has ended until the start of the next rainy season; it will only be updated during this time as needed. && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...Small Craft Advisory from 2 PM this afternoon to 5 AM PDT Tuesday for Central U.S. Waters Strait Of Juan De Fuca- East Entrance U.S. Waters Strait Of Juan De Fuca. && $$

332 FXUS66 KPQR 182030 AFDPQR Area Forecast Discussion National Weather Service Portland OR 130 PM PDT Mon May 18 2026 .SYNOPSIS...Dry and benign weather is expected across the region through much of the next week as high pressure builds over the Northeast Pacific, resulting in a warming trend. Weak systems aloft may bring enhanced cloud cover on some days, but rain chances are minimal. && .DISCUSSION...Now through Sunday night...Concerns for hazardous weather remain minimal through the upcoming week. There is high confidence that upper-level ridging and surface high pressure will build over the Northeast Pacific, although uncertainty in the amplitude and position of the upper ridge increases later in the forecast period. Through the end of the workweek, while the ridge axis remains well offshore, upper shortwaves within northwesterly flow aloft may produce increased cloud cover on certain days including Tuesday into Wednesday morning, but chances for rainfall remain 5-10% along the Clatsop and Pacific County coasts and in the Willapa Hills, and lower elsewhere. On clearer nights, areas of fog are most likely to develop within sheltered valleys. As the ridge axis shifts east, temperatures will trend upward through at least Thursday, reaching the 60s on the coast and upper 70s to low 80s along the I-5 corridor. At this time, there is Minor HeatRisk forecast across the region, meaning those who are most sensitive to heat may be affected, however there are 15-25% chances Moderate HeatRisk occurs in some urban areas along I-5 if daytime highs end up slightly hotter, including the Portland/Vancouver metro, Salem, and Albany/Corvallis areas. Later in the forecast period, from Friday through next weekend, uncertainty in the evolution and possible break-down of the upper-level ridge introduces similar uncertainty in forecast temperatures and precipitation. Forecast daytime highs currently trend downward through the holiday weekend as chances increase that ridging deamplifies or is replaced by an upper trough, but there is an increasingly wide range of possible outcomes. The 80%-confidence envelopes (the difference between the 10th and 90th percentiles) in temperature widen from 8-13 degrees on Friday and Saturday to 16-18 degrees on Sunday and Monday along the I-5 corridor. There is greater consensus that the ridge will break down late Sunday into Monday, yielding increasing chances of cooler temperatures as well as the highest chances of rainfall, 25-50%, in over a week. -36 && .AVIATION...High pressure will maintain fair conditions with high level clouds moving overhead through the day. Northwest flow of 5-10 kt through the day with wind gusts along the coast up to 20 kt possible. Winds relax this evening and overnight. Marine stratus pushed back toward the coast this evening, mainly along the northern Oregon and southern Washington coast. Probabilities increase to 60-90% for development between 02-06z Wednesday for KAST and much lower at 20-30% for KONP. Guidance suggests stratus developing along the Columbia River toward the Portland/Vancouver Metro between 10-1z Wednesday. KPDX AND APPROACHES...VFR conditions expected through at least 06z Tuesday. High clouds expected to clear out this afternoon. Light northwest winds expected to increase to 8-10 kt by 22z this afternoon. Stratus pushing inland along the Columbia River could reach the metro between 10-16z Tuesday with a 30-60% chance for sub-VFR CIGs, mainly for KTTD and KPDX. -19 && .MARINE...Northerlies are expected to persist through much of the week as the summer-like pattern settles in. Strongest winds are expected during the afternoon and evening periods as a surface thermal trough strengthens over the southern Oregon coast. A Small Craft Advisory is in effect for the inner coastal waters south of Cape Foulweather later this afternoon into this evening for gusts up to 25 kt. Similar conditions are expected on Tuesday. Seas around 6 to 8 feet are expected through the week as well. Chances increase on Wednesday and Thursday for more widespread wind gusts for all marine zones. Small Craft Advisories is in place for the Columbia River Bar for early Tuesday morning due to strong ebb currents which will produce conditions hazardous to small craft. Strong ebb currents are possible during the morning hours each day this week. -19/DH && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...Small Craft Advisory from 5 AM to 9 AM PDT Tuesday for PZZ210. Small Craft Advisory until 11 PM PDT this evening for PZZ253. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland x.com/NWSPortland

047 FXUS66 KMFR 182116 AFDMFR Area Forecast Discussion National Weather Service Medford OR 216 PM PDT Mon May 18 2026 .DISCUSSION (Today through Sunday)... Key Points: * Minor impacts continue the next several days - Return of well above normal temperatures tomorrow - These above normal temperatures continue through the weekend * Drying trend continues through the extended forecast - No signal for precipitation in the forecast at this time * Elevated fire weather concerns this week - Combination of dry, breezy, and warm temperatures - Fuels fortunately keeping the overall fire threat low/moderate Further Details: A ridge of high pressure will maintain its position over the Pacific Ocean through the extended forecast. While occasional troughs pass over the northern tier of this high pressure, these will mainly impact Washington and southwest Canada. As a result, a dry and stable airmass is likely to persist this week. The position of the high and an area of low pressure inland will result in a strong pressure gradient over the forecast area (thermal trough) through this stretch, so expecting diurnal breezy afternoons each day. That said, it doesn`t appear any hazards will result from these wind speeds. As we maintain the dry airmass and breezy afternoons, there will be at least an elevated threat for fire weather conditions each day. However, fuel conditions per fire agencies reveal the overall fire weather threat will remain low to moderate. Given the low RH values and breezy winds each afternoon, people should exercise caution with any outdoor activities that could cause sparks or flames. Bottom line is that fire season was declared early this year, so these precautionary actions should already be in place, but its especially important when we have these elevated fire weather days. Looking ahead, there is a chance for a change in the airmass around Memorial Day that could bring precipitation chances across the forecast area. This is technically outside of this forecast package, but something we will keep an eye on given the lack of precipitation lately. However, models are split on these chances so this is nothing of a "slam dunk" scenario. && .AVIATION (18Z TAFs)... VFR conditions are expected at all terminals throughout the valid TAF cycle. Northwesterly flow aloft is anticipated through this cycle as high pressure maintains over the Pacific. Main thing this cycle will be the breezy wind speeds this afternoon, but not expecting these speeds to continue after sunset with speeds decreasing overnight in a typical diurnal fashion. && .MARINE...Updated 200 PM PDT Monday, May 18, 2026...A thermal trough will bring gusty north winds and steep to very steep seas over the coastal waters much of this week. Winds will be strongest and seas will be highest during the afternoons/evenings. Through this stretch, very steep seas of 10-12 ft are most likely south of Cape Blanco with steep seas (6-9 ft) north of Cape Blanco. Ensembles indicate winds will strengthen Wednesday through Friday with a potential (35-55% chance) for gales (gusts) across portions of the southern waters, especially from around Gold Beach south. && .MFR WATCHES/WARNINGS/ADVISORIES... OR...CA...None. PACIFIC COASTAL WATERS...Hazardous Seas Warning until 11 PM PDT Wednesday for PZZ356-376. Small Craft Advisory until 11 PM PDT Wednesday for PZZ350-370. && $$

903 FXUS66 KEKA 180741 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 1241 AM PDT Mon May 18 2026 .SYNOPSIS...Gusty north winds continue to ease today. Clear and dry conditions will remain through the week with a warming trend through Thursday. && .KEY MESSAGES... -Strong north winds will weaken today and through the week with only moderate north winds close to shore. -Generally clear skies and dry conditions, even along shore, through the week. -Conditions will warm through Thursday with highs in the interior peaking near 90. .DISCUSSION...Strong north winds continue to subside for Northwest California, especially near shore when compared to yesterday, but will persist through early today around the rim of the Sacramento Valley, especially Lake County. Strong mixing will continue to keep skies clear as temperatures begin to warm, especially across the interior. Wind overnight will continue to preclude any frost formation. High pressure will already begin to weaken but move more onshore today and through the week. This will lead to much weaker north winds with some moderate gusts to 20 mph still pushing in right along shore in the afternoon. Interior winds will transition to a more terrain controlled regime. Conditions will remain very dry with warming temperatures through the week. Highs will most likely top out around 90 for the interior on Thursday. This will constitute only a minor HeatRisk for this time of year. Hotter temperatures will help reform a marine inversion. Any stratus and fog; however, will most likely be very shallow and mix out quickly during the day. Compared to previous runs, most ensemble members continue to show a weak trough in the far extended forecast, but have it delayed until after next week. Rather most models show high pressure slowly weakening, allow temperature to drop, through next weekend. A trough early next week could bring some light showers or thunderstorms, but the vast majority of models currently remain dry. /JHW && .AVIATION...VFR conditions are expected for terminals in Northwest California as gusty north winds remain elevated, but quickly diminish early this morning. Winds will remain elevated for higher elevation areas of the Yolla Bollys and Lake County. Winds have diminished for more protected areas; however, winds remain elevated aloft, bringing LLWS concerns mostly for Mendocino County. && .MARINE...The pressure gradient relaxes slightly and the strongest winds move farther off the coast as the high pressure builds in. However, a large area of gale force gusts around 34-45 kts expected across all zones, with the strongest winds downwind of Cape Mendocino. Steep to very steep, hazardous seas will continue with the elevated winds. Conditions will remain hazardous across the waters for much of the workweek with strong to gale force gusts north winds and steep to very steep seas. Gale force winds and very steep seas are forecast to persists across the outer waters through Friday. /ZVS && .FIRE WEATHER...Strong north winds will continue, but diminish into the early morning. Winds will especially remain elevated around the rim of the Sacramento Valley and in Lake County today. Winds will weaken by this evening and transition to more gentle terrain wind through the week. Conditions will remain very dry with high temperatures increasing to near 90 for the interior by Thursday. && .EKA WATCHES/WARNINGS/ADVISORIES... CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Gale Warning until 3 AM PDT early this morning for PZZ450- 455. Gale Warning until 3 AM PDT Wednesday for PZZ470-475. && $$ 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

195 FXUS66 KMTR 181958 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 1258 PM PDT Mon May 18 2026 ...New SHORT TERM, LONG TERM, FIRE WEATHER... .KEY MESSAGES... Updated at 1251 PM PDT Mon May 18 2026 - Breezy to windy conditions, especially across the North, East, and South Bay Mountains and the Santa Cruz Mountains continue through tonight - Elevated fire weather concerns continue through today across the interior due to very dry conditions and breezy winds - Above normal temperatures continue through midweek with seasonal temperatures returning late week && .SHORT TERM... Issued at 1251 PM PDT Mon May 18 2026 (This evening through Tuesday) Gusty offshore winds have started to come down across the region and will continue to ease through the remainder of the day. Current gusts across the lower elevations are peaking around 25-30 mph with gusts across the higher elevations peaking between 35-45 mph. The strongest gust observed during this wind event was 86 mph right around midnight at Mt. Umunhum where the station is at an elevation of 3319 feet. This tracks pretty well with when the SFO-WMC pressure gradient peaked (-7.60 mb) around 1AM and again around 5AM. The SFO- WMC gradient is currently around -4.3 mb and is expected to continue easing through the remainder of the day. Winds remain lightly offshore across the interior through the remainder of today into tomorrow but winds will be weaker. We will see a return to our normal breezy afternoon/evening winds that ease overnight starting Tuesday. Upper level ridging continues to dominate the Pacific Ocean while broad upper level troughing prevails over the Western United States. At the surface, high pressure prevails over the Pacific while a coastal trough develops along the California coast. Warmer temperatures are expected to continue Tuesday through Thursday. This is thanks both to ridging offshore suppressing the marine layer and a warmer, drier airmass moving in in the wake of this weekend`s strong offshore winds. Interior high temperatures will generally be in the 80s with the hottest portions of the North and East Bays in the low 90s. Coastal areas will be slightly cooler in the 60s to mid 70s. Dry conditions are expected to prevail through much of the upcoming week with daytime relative humidity values dropping into the 10`s to 20`s. While fire weather concerns are lower now that the winds are easing, fine fuels (grass, shrubs) are dried out and are ready to burn. If you are engaging in any outdoor activities involving flames or are towing something, keep a close eye on it and prevent sparks from spreading. && .LONG TERM... Issued at 1251 PM PDT Mon May 18 2026 (Tuesday night through next Sunday) The overall pattern remains the same for much of the upcoming week. High temperatures will stay above seasonal normals through Thursday with highs in the 80s to low 90s across the interior and 60s to 70s along the coast. Patchy moderate heatrisk is forecast across urban areas but it is note widespread enough to necessitate a Heat Advisory. If you are spending time outdoors this week make sure to drink plenty of water and take breaks in the shade as needed. Winds generally remain offshore with diurnally breezy conditions expected. Friday into the weekend a pattern change looks likely. Long range guidance suggests upper level ridging will weaken and shift westward over the Pacific while broad upper level troughing dominates the West Coast. With high pressure shifting away, onshore winds return and the marine layer will be able to redevelop by late week. A shallow (~500 ft) marine layer will redevelop mid to late week but will deepen to ~1000 ft by Friday. This, and receding high pressure, will kick off a cooling trend with interior temperatures returning to the 70s to low 80s and coastal areas to the 60s. The return of the marine layer will help to alleviate dry daytime conditions, further reducing fire risk late next week. && .AVIATION... (18Z TAFS) Issued at 1021 AM PDT Mon May 18 2026 VFR conditions prevail through the TAF period. Breezy and gusty northeast winds will gradually diminish through the next couple of hours as an onshore push returns to the coastal regions this afternoon, with the coastal breeze continuing through the evening. Breezy winds will continue across the interior mountains of the Bay Area through the night, with northeast winds spreading across the interior valleys Tuesday morning towards the end of the 24-hour TAF period. Beyond that, Tuesday`s coastal breezes look to be stronger than today`s. Vicinity of SFO... VFR conditions through the TAF period. Breezy and gusty northeast winds will turn more northwesterly through the afternoon, before diminishing through the evening and remaining light overnight through Tuesday morning. West-northwest winds will resume on Tuesday afternoon. SFO Bridge Approach... Similar to SFO. Monterey Bay Terminals... VFR conditions through the TAF period. Breezy northwest winds will develop imminently and continue into the evening. Winds remain light overnight before resuming Tuesday afternoon after the end of the TAF period. && .MARINE... (Today through Saturday) Issued at 1021 AM PDT Mon May 18 2026 Winds continue to diminish throughout the marine environment, but moderate to rough seas and moderate to fresh northwest breezes will still offer hazardous conditions for small craft into the mid weak before easing for most zones. Fresh to strong northwest breezes will remain hazardous for small craft into the late week for the northern outer zone. && .FIRE WEATHER... Issued at 1251 PM PDT Mon May 18 2026 Gusty north to northeast winds will continue through this afternoon before easing tonight into tomorrow. Peak gusts between 35 to 45 mph are still possible across the higher elevations into this evening. Daytime humidity retention remains poor with most sites staying around 10-25% across the interior and higher peaks with limited overnight recoveries. Winds ease by Tuesday but fire weather concerns will linger through late week as light offshore flow continues and daytime humidities remain poor. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...Coastal Flood Advisory until 3 AM PDT Tuesday for CAZ506. PZ...Small Craft Advisory until 3 PM PDT this afternoon for SF Bay N of Bay Bridge. Small Craft Advisory until 9 PM PDT this evening for Mry Bay- Pigeon Pt to Pt Pinos 0-10 nm. Small Craft Advisory until 3 AM PDT Tuesday for Pt Arena to Pt Reyes 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm. Small Craft Advisory until 9 PM PDT Wednesday for Pt Arena to Pt Reyes 10-60 NM. Small Craft Advisory until 9 AM PDT Tuesday for Pigeon Pt to Pt Pinos 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

846 FXUS66 KOTX 182041 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 141 PM PDT Mon May 18 2026 .KEY MESSAGES... - Pop up showers and isolated thunderstorms primarily Northeastern WA and North Idaho Tuesday afternoon. - Chilly overnight temperatures will bring an isolated threat of morning frost Tuesday. This could impact sensitive plants or crops. - Conditions trend drier and warmer through the workweek regionwide, with periodic breezy winds for the Cascades and central WA. && .SYNOPSIS... Showers with isolated afternoon thunderstorms will continue Tuesday. Precipitation chances decrease and afternoon highs trend warmer through the workweek, climbing back into the 70s and 80s by Thursday and continuing through next weekend. Breezy winds are expected at times through the Cascade gaps and across the western Columbia Basin. && .DISCUSSION... Tonight - Wednesday: The combination of afternoon heating and residual moisture will keep a threat for showers and thunderstorms this evening across Northeastern WA and North. Storm motion to the south and southeast does bring a small threat for a few cells to drift off the higher terrain and into the Upper Columbia Basin and Spokane-Cd`A area. The depth of the convection is slowly shrinking at temperatures warm 2-3 Celsius at 500 mb so updrafts are largely growing to -25C versus -35C on Sunday. Ideally, this will result in less lighting strikes across the area. The strongest cells will be capable of brief downpours of rain/small hail and wind gusts around 30 mph. Overnight lows will be a few degrees warmer Tuesday morning but still cooling into the 30s to 40s. The threat for frost will be more localized. If you experienced temperatures in the low 30s and frost Monday morning, may want to consider taking actions to protect sensitive plants again. Given the complex terrain of our region, many observation platforms are not dipping to freezing given the placement of the sensor above ground but frost has been reported nearby, especially where there are low spots. The current frost forecast has a 20-25% chance for frost in the valleys of NE WA and N ID (down from 40-50% Monday). One change for tonight will be the potential for midlevel clouds moving through NE WA and N ID overnight which would support the idea of warmer temperatures. On Tuesday, temperatures continue to warm aloft for most areas away from far NE WA and N ID. This will equate to less shower activity region-wide and mainly fair cumulus build ups. Upper levels will be slower to warm over far NE WA and N ID. Locations like Ione, Porthill, and Bonners Ferry will maintain a 15-25% chance for showers and t-storms. High pressure begins to amplify along the coast Wednesday. Midlevel flow buckles from northwest to north over the INW. A cooler shortwave will drop down the eastern flank of the ridge and along the Northern Rockies. This will bring a threat of showers and thunderstorms back to the ID/MT border Wednesday afternoon. If the wave is a bit deeper and further west, the threat for convection may need to be expanded as far west as the ID/WA border. Breezy northerly winds will develop Wednesday night with this system with gusts of 20-30 mph for locations like Omak, Ephrata, and Wilbur. Thursday-Monday: There is moderate confidence for the upper-level ridge to build into the region Thursday and linger into Friday delivering a warming and drying trend. Details become a bit more uncertain over the weekend and early next week when additional shortwaves begin swinging into the region from the Gulf of AK. There are many variations with timing and strength of these systems. Any systems will need to be monitored closely for potential showers and thunderstorms along with gusty winds, especially if there is a quick exchange of air masses. Ensemble means are hinting wind gusts around 30 mph right now across the Basin and Spokane Area with a handful of members in the 40-45 mph range. Monday is the windiest day at this time. /sb && .AVIATION... 18Z TAFs: Antecedent boundary layer moisture and surface heating will result in developing cumulus fields 18-20Z. There is 40% chance for cells to develop showers and 10-25% for convection to grow deep enough for lightning. Greatest risk will be over the mountains of northern WA and the Idaho Panhandle though cells drifting south will pose a small risk into the upper Columbia Basin and Spokane-Cd`A area. Given the latest output from the cam models, did introduce prob30 for KGEG-KSFF-KCOE for -shra with a 10-15% chance for -tsra. Any thunderstorms will bring a threat for brief downpours of rain/small hail, lightning, and erratic outflow winds to 30 mph. Pending where rain falls, areas of valley fog will be possible overnight. FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: There is a small risk for MVFR cigs mainly around KGEG-KSFF- KCOE-KPUW this morning as cumulus clouds are developing and cloud bases are slowly lifting. Main uncertainty this afternoon will be if thunderstorms survive off the higher terrain into KGEG-KSFF-KCOE as we have seen the last two afternoons. /sb ----------------------- 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 41 68 44 71 43 72 / 20 0 0 0 0 0 Coeur d`Alene 41 66 44 68 43 70 / 20 10 0 0 0 0 Pullman 39 64 42 66 41 69 / 0 0 0 0 0 0 Lewiston 43 70 46 72 46 75 / 0 0 0 0 0 0 Colville 36 70 40 74 38 75 / 20 20 10 0 0 0 Sandpoint 40 65 43 67 41 70 / 20 10 10 10 0 0 Kellogg 39 65 43 67 42 70 / 20 10 0 10 30 0 Moses Lake 41 74 45 78 48 79 / 0 0 0 0 0 0 Wenatchee 48 73 50 77 53 78 / 0 0 0 0 0 0 Omak 43 74 47 77 48 78 / 0 10 0 0 0 0 && .OTX WATCHES/WARNINGS/ADVISORIES... WA...None. ID...None. && $$

562 FXUS66 KPDT 182011 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 111 PM PDT Mon May 18 2026 .KEY MESSAGES... - Scattered showers and isolated thunderstorms over Wallowa County today - Breezy to locally windy westerly winds through the Cascade gaps today and Tuesday - Warming and mostly dry Tuesday through the week && .DISCUSSION... Daytime heating has led to modest instability (surface-based CAPE of a couple hundred J/kg or less per SPC`s RAP-based mesoanalysis and forecast soundings from the 12Z HREF/REFS) this afternoon across the Blues and Washington Cascades. While activity has been isolated elsewhere, scattered rain showers have developed across Wallowa County. Through evening, there is a slight chance (15 percent) of thunder across Wallowa County, with lower (5-10 percent) chances of rain showers and thunder for other parts of the Blues as well as the Washington Cascades. Tuesday through Saturday, warming temperatures and mostly dry conditions are forecast region-wide as an upper-level ridge of high pressure will likely (90-95 percent chance) build into the region from the Pacific and dominate the weather. A couple weak shortwaves passing through northwesterly flow aloft coupled with modest diurnally induced instability (surface-based CAPE of a up to a couple hundred J/kg from forecast soundings) may facilitate some isolated showers for the mountains through Thursday, but PoPs are low (10 percent or less). Breezy to locally windy westerly winds are forecast through the Cascade gaps today and Tuesday, but not anticipating a need for any wind headlines. In yesterday`s discussion, mentioned the potential for westerly winds to meet advisory criteria on Thursday. Ensemble guidance has since trended towards a solution that would lead to a wind reversal to mostly light northeasterly (offshore) winds late Wednesday and Thursday as a shortwave digs south across the northern Plains and Rockies, just clipping the edge of our forecast area. Considering there is still some ensemble spread, will place confidence in this solution at medium (60 percent). Considerable uncertainty in the 500-hPa pattern is present in ensemble solutions by the weekend, with roughly 45-50 percent of the variance in solutions explained by timing differences among solutions regarding the arrival of a trough or closed low from the Pacific. The NBM has westerly winds returning to the region by late Friday, persisting through the weekend. Highest chances (10-40 percent) of reaching advisory-level winds have now been pushed back to Saturday and Sunday through wind-prone areas of the lower elevations, primarily the eastern Columbia River Gorge, north-central Oregon, the foothills of the Blue Mountains, and the Kittitas Valley. Of course, the magnitude of winds will be tied to the synoptic pattern, and given the uncertainty (see paragraph above), can`t really talk about much confidence in forecast details yet. && .AVIATION /18Z TAFS THROUGH 18Z TUESDAY/... VFR conditions are forecast for the next 24 hours at all sites. Winds will be diurnally and terrain-driven, breezy from late morning through evening. There is a very low (10 percent) chance of rain showers this afternoon at YKM with even lower chances (5 percent or less) elsewhere. && .Preliminary Point Temps/PoPs... PDT 42 72 46 73 / 0 0 0 0 ALW 46 72 49 73 / 0 0 0 0 PSC 44 77 48 79 / 0 0 0 0 YKM 44 76 47 79 / 0 0 0 0 HRI 44 75 48 77 / 0 0 0 0 ELN 41 68 43 73 / 0 0 0 0 RDM 30 72 37 74 / 0 0 0 0 LGD 36 68 40 70 / 0 0 0 0 GCD 34 71 38 74 / 0 0 0 0 DLS 45 74 49 78 / 0 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... WA...None. OR...None. && $$ DISCUSSION...86 AVIATION...86

552 FXUS65 KREV 182025 AFDREV Area Forecast Discussion National Weather Service Reno NV 125 PM PDT Mon May 18 2026 .KEY MESSAGES... * Expect widespread freezing to near freezing temperatures on Tuesday morning. * A ridge builds back into the region by mid-week, allowing for warmer and drier conditions into the weekend. && .DISCUSSION... * Today is on the chilly side across the region with below average temperatures and brisk north-northeast winds. Low temperatures tonight will fall between 30-40 degrees in western NV, and 20-30 degrees for the eastern Sierra communities. These readings are a few degrees warmer compared to Monday morning, but still around 5-10 degrees below average. Winds will remain east to northeast into the Tuesday, but will subside in strength by tonight. * A gradual warming trend will resume on Tuesday and continue into the weekend. High pressure in the east Pacific will slowly expand east over the region, which will increase atmospheric thicknesses and 500mb heights. This will allow for temperatures to trend up into the low to mid-80s in western NV and eastern Lassen County, and the mid to upper 70s for the eastern Sierra communities. This will be accompanied by much lighter winds, and dry weather. * For the upcoming Memorial Day weekend, the ensembles show anything from ridging with dry conditions and above average temperatures, to a trough pattern that is wetter and cooler. So, keep informed of the changes to the forecast this week as we approach the holiday weekend. -McKellar && .AVIATION... VFR conditions expected for all terminals today with breezy east/northeasterly afternoon winds (gusts up to 20 kts), albeit not nearly as strong as the winds yesterday. -Giralte/McKellar && .REV Watches/Warnings/Advisories... NV...None. CA...None. && $$

632 FXUS66 KSTO 181830 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 1130 AM PDT Mon May 18 2026 .KEY MESSAGES... - Red Flag warning expires this evening. - Less wind rest of the week but above normal temperatures returning with widespread moderate heat risk Thursday. && .DISCUSSION... ...Tonight and Tuesday... The upper trough/inside slider that brought us widespread gusty winds is quickly moving off to the east and causing severe weather in the central U.S. This will shift upper winds from the north to a more zonal westerly directions. In other words, less wind for the rest of the week. Relative humidities will remain low this week but not as dry as today. Once the pattern settles in on Tuesday/Wednesday it looks to stay pretty consistent. Warmest day looks to be on Thursday with very little spread in maximum temperature in the NBM percentiles. Currently looks like widespread moderate heat risk with temperatures in the 90s to approaching 100 in the north. Confidence pretty high that temperature forecast shouldn`t change too much. HeatRisk probabilities very low to reach above moderate risk but will keep an eye on this. Things look to cool down enough Friday into the weekend but still very warm. No rain in site right now in the 7 day forecast. && .AVIATION... VFR conditions are expected over the next 24 hours. Northerly winds 15-20 kts with gusts 20-30 kts for the Valley and Delta until around 00z-03z Tuesday. Northeast to east wind gusts up to 20-35 kts through mid-day today. && .STO WATCHES/WARNINGS/ADVISORIES... Red Flag Warning until 8 PM PDT this evening for Butte County Below 1000 ft-C. San Joaquin County including Stockton-C. Solano County including Fairfield-C. Stanislaus County including Modesto-C. Yolo/NE Solano including Woodland-Central Colusa County Incl. I-5-Central Glenn Co & Interstate 5-Eastern Colusa County-Eastern Glenn County-N. Sac Valley in Tehama County-NE San Joaquin Valley Below 1000 ft-SW Solano County including Vallejo-Sac Metro/W. El Dorado/Amador County-Sacramento County Delta-San Joaquin County Delta-Shasta Metro-Sutter/Yuba counties below 1000 ft-Tracy Triangle Below 1000 ft-W. Stanislaus County Above 1000 ft & I-5-W. Yolo County including Capay/I-505. && $$

459 FXUS65 KMSO 181936 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 136 PM MDT Mon May 18 2026 .DISCUSSION... KEY MESSAGES: - Showers with a few thunderstorms(20-50% chance) today through Wednesday, especially across northwest Montana and over the Continental Divide. - Frost/freeze concerns remain for Tuesday morning. - Mountain snow above 6000 feet with raw/cold backcountry conditions later Wednesday into Thursday morning over the Divide, Glacier National Park, extending west towards the Idaho border. - Return to summer-like conditions as moderating temperatures are expected late week into next weekend. Temperatures this morning were quite cold across the region. Whenever you get such a cold trough originating from the northern latitudes like Alaska, you almost have to expect possible frosty mornings. The Ravalli County Airport located northeast of Hamilton saw a low of 21 degrees! Looking back at climatology, its really not that uncommon to get these types of systems in May where highs struggle to get out of the 30s and 40s. Looking at the climatology for the Hamilton area for the second half of May the coldest low temperature recorded was 24 degrees set on May 22, 2010. The Stevensville COOP recorded a 15 degrees on May 30, 2001. Even other locations, like the higher 3000 feet valleys in Idaho were in the upper 20s this morning. With the chance for frost continuing into Tuesday morning, we issued more frost advisories. We listed the percentile ranges of low temperatures for select locations in the "additional details" section to help people make decisions on if they need to cover things or not. For those who are unaware, we typically will not issue frost/freeze advisories for the high valleys(i.e. southwest Montana/Divide) that will continue to have sub- freezing nights for the remainder of May until the climatological last frost/freeze day. If we get a cold system thereafter, we may choose to issues advisories then. For the next two days, we`ll be under cyclonic flow with disturbances dropping out of southern British Columbia. There is generally a 20 to 50 percent chance for lightning over the mountains of northwest Montana this afternoon and evening. Other impacts from the showers will be gusty winds to 35 mph in the stronger cells. Then shortwave energy from the Gulf of Alaska will carve a larger upper level trough which digs over Montana later Wednesday into Thursday. With the colder temperatures aloft, this will drive the snow levels down to around 6000 feet. This could bring additional snowfall to the mountains over the Divide, including Glacier National Park. Also the associated cold front will shift south and west with time just after peak heating which will allow for possible showers and thunderstorms. The latest probabilities show the best instability present across northwest Montana. This system will basically move off into the Northern Plains by Thursday into Friday while we will have rising heights (moderating temperatures). A general ridge will build by next weekend and temperatures will rise back into the 70s and 80s across the region. There is a hint that a trough may either bring mild and windy conditions on Sunday, or dig across the region by early next week. && .AVIATION...Scattered showers and thunderstorms will be possible today across the region. The more intense cells will be found across northwest Montana, especially initiated over the mountains. They will have a general storm motion from northwest to southeast around 23 knots. Main impacts will be isolated lightning, brief visibility reduction and gusty winds to 30 knots. A few lingering showers are possible tonight across northwest Montana thanks to a shortwave dropping out of British Columbia. There could be patchy fog along river bottoms elsewhere Tuesday morning. Another round of showers with a few thunderstorms are expected Tuesday afternoon and evening with the focus over the Divide and points west. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...Frost Advisory from midnight tonight to 9 AM MDT Tuesday for Bitterroot/Sapphire Mountains...Flathead/Mission Valleys... Lower Clark Fork Region...Missoula/Bitterroot Valleys. ID...Frost Advisory from midnight MDT /11 PM PDT/ tonight to 9 AM MDT /8 AM PDT/ Tuesday for Eastern Lemhi County...Northern Clearwater Mountains...Southern Clearwater Mountains. Frost Advisory from 11 PM this evening to 9 AM PDT Tuesday for Orofino/Grangeville Region. && $$

208 FXUS65 KBOI 182042 AFDBOI Area Forecast Discussion National Weather Service Boise ID 242 PM MDT Mon May 18 2026 .KEY MESSAGES... - Frost Advisory for the western Magic Valley Tuesday morning. - Lighter winds and drier with a gradual warming trend through Wednesday. - Generally dry with above normal temperatures through the weekend. Potential pattern change early next week. && .SHORT TERM /Through Wednesday Night/... The afternoon/evening showers and isolated thunderstorms will diminish with sunset, as will the gusty winds. Lighter winds and clear skies overnight allow for possible frost in the western Magic Valley Tuesday morning. There is a spread in forecast low temperatures with a range of 33 to 38 in the Gooding/Jerome/Twin area so coverage could be patchy. Have opted with a Frost Advisory to highlight the potential. Building heights behind the exiting trough will bring a gradual warming trend with high temperatures close to normal by Wednesday. Mountains will see an afternoon cumulus field from daytime instability. Can`t rule out a mtn top shower over w-central Idaho mtns (east of McCall- Lowman-Atlanta line) each afternoon, but it would be light with heavier development further north and east. An approaching trough will increase precipitation chances across these areas Wednesday night. Winds settle down Tue/Wed staying below 15 mph for most sites. && .LONG TERM /Thursday through Monday/... Come Thursday, a shortwave embedded in the northwesterly flow aloft will begin to dig into southeastern Idaho. While the better forcing associated with this shortwave will be east of our area, height falls aloft will support isolated showers developing over higher terrain in the West Central and Boise Mountain zones. Following this trough, dry northwest flow will return with higher pressure building in aloft over the Pacific; as a result, a warming trend will set in through the weekend, with temperatures 5-10 degrees above normal. Come Sunday, flow aloft will become more zonal as a Gulf of Alaska low deepens. The exact track of this low is a bit uncertain this far out; however, the grand ensemble shows the indication of troughing moving across our area come early next week (deterministic guidance varies on strength and track). Despite the uncertainty, the signal is there for a pattern change early next week, this will lead to increasing precipitation chances and cooler temperatures (although still leaning above normal) come Monday. With the main jet stream above our area throughout the long-term period, breezy conditions will stick around each afternoon. The windiest conditions of the period will likely come early next week as the low makes it`s way into our area. && .AVIATION /18Z Monday through Tuesday/... Issued 1155 AM MDT MON MAY 18 2026 VFR. Scattered showers this afternoon, mainly across higher terrain. Brief MVFR/IFR conditions and mtn obscuration in showers. Snow levels: 5.5-6.5 kft MSL. Surface winds: W-N 5-15 kt with gusts to 20-25 kt this afternoon. Becoming variable 5-10 kt overnight. Winds aloft at 10kft MSL: N 10-20 kt. KBOI...VFR. Showers over the foothills this afternoon. Surface winds: NW 10-20 kt with gusts up 28 kt this afternoon, becoming SW-NW up to 8 kt overnight. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...Frost Advisory from 4 AM to 8 AM MDT Tuesday for IDZ016. OR...None. && $$ www.weather.gov/Boise Interact with us via social media: www.facebook.com/NWSBoise www.x.com/NWSBoise SHORT TERM...DG LONG TERM....NF AVIATION.....NF

175 FXUS65 KLKN 181957 AFDLKN Area Forecast Discussion National Weather Service Elko NV 1257 PM PDT Mon May 18 2026 .KEY MESSAGES... * Temperatures will be cold with below normal readings at all locations today * A slow warmup will start today and persist through the rest of the week * Storm system will clip NV Thursday and Friday may bring a few isolated showers. * Memorial Day Holiday Weekend looking Quiet with light winds and highs in the upper 70s to upper 80s. && .DISCUSSION... (This evening through next Sunday) Quiet weather returns this week as NW flow aloft looks to keep NV dry, allowing for temperatures to warm back into the 80s by the Weekend. Overall weak troughing pattern over the interior Mountain west will keep northwesterly flow aloft over the great basin through next weekend. Monday through Wednesday look to be dry with light to breezy NW winds. Thursday a quick moving upper trough will ride the NW flow, bringing a wind shift line through Nevada, but models keep this system far enough to the NE that only the far NE Elko county could see a 10% chance for a light shower Thursday afternoon, this front will stall across central NV and this may be enough to generate a isolated shower for the mountains of N Nye county Friday. After Friday dry conditions return for the weekend lasting through Memorial Day. The main story this week will be the temperatures as the cold air mass left in the wake of Sundays storm system begins to modify and warm. Highs will start cool in the upper 50s to upper 60s Monday afternoon and warm through the week back into the mid 70s to mid 80s by Friday afternoon. Lows will gradually warm as well starting in the low 20s to low 30s Tuesday morning the rising back into the mid 40s to mid 50s by the Saturday morning. FORECAST CONFIDENCE & DEVIATIONS: There is high confidence for quiet, dry weather conditions with warming temperatures lasting through the Holiday weekend. There is low confidence for isolated showers across far NE NV Thursday afternoon, and for N Nye county Friday afternoon as a weak upper trough pushes a wind shift line through NV. && .AVIATION... VFR conditions are forecast through Tuesday evening with light to breezy afternoon northerly winds. KEKO remains AMD NOT SKED due to communication disruption. && .FIRE WEATHER... Low fire weather concerns over the next few days as northwesterly flow aloft keeps quiet dry conditions with warming temperatures for most of the week. A weak storm system will try and clip NV Thursday afternoon and Friday, however models want to keep this system well to our north, but there could be a low 10% chance for an isolated shower. Saturday through the Memorial Day holiday look to be quiet with highs in the upper 70 to low 80s. Winds will feature light to breezy afternoon winds, generally out of the WNW at 5 to 15 MPH with a few gusts up to 25 MPH possible. && .LKN Watches/Warnings/Advisories... None. && $$ DISCUSSION...98 AVIATION...98 FIRE WEATHER...98