Area Forecast Discussion
Issued by NWS Spokane, WA
Issued by NWS Spokane, WA
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182 FXUS66 KOTX 272150 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 250 PM PDT Mon May 27 2024 .SYNOPSIS... Tuesday will see a return of showers and thunderstorms to Eastern Washington and Idaho Panhandle. A few storms could be strong with gusty outflow winds in southeastern Washington and the Idaho Panhandle. Cool and showery conditions continue through the end of the week with drier and warmer conditions at the start of the upcoming weekend. && .DISCUSSION... Today and tomorrow: Today is shaping up to be a very nice day in the Inland Northwest. Temperatures are 8 to 19 degrees warmer than yesterday in the 70s and low 80s. Cirrus clouds are thickening over deep southwest flow ahead of a shortwave trough off the coast of British Columbia. The main focus tomorrow will be widespread thunderstorms that may be strong in the afternoon. Storms will be capable of frequent lightning, large hail, and gusty winds. The main window for strong storms will be around noon to 10 PM tomorrow with an early focus on the northern mountains and a later focus on southeast Washington and the southern ID Panhandle. A complicating factor for tomorrow is that models show elevated showers come through overnight tonight in Eastern Washington and North Idaho. The main question is how will this limit day time heating for stronger storms tomorrow afternoon via cloud cover. Models suggest it will inhibit activity a little later than usual but I have witnessed them firing thunderstorms 1 to 3 hours too late around here. Cells will be moving fast but new storms being initiated on the same mountain peaks may lead to a flash flood threat as well given a fairly moist atmosphere. Wednesday through Friday: A trough oflow pressure will be established over the region on Wednesday delivering cooler than normal temperatures and widely scattered showers around the outer rims of the Columbia Basin and across the mountain zones. A few weak thunderstorms will also be possible. Initially, these will be more of the hit or miss variety forming with the assistance of afternoon heating however by the late afternoon and evening, several models continue to forecast a shortwave rounding the base of the trough. This could create more organized bands of showers and embedded thunderstorms. Any storms will be capable of lightning, brief downpours of small hail/rain, and wind gusts up to 30 mph as the main threats. The air mass will be cool with snow levels near 4000 feet. The heaviest cells will be capable of a quick 0.25" of rainfall. Blustery west to southwest winds will be in place Wednesday. Sustained winds across the Columbia Basin and through the Cascade Gaps will remain in the 15-20 mph range with gusts up to 35 mph. Most other areas will be closer to 10-15 mph with gusts around 25 mph. The trough begins to drift eastward on Thursday with shortwave ridging moving toward the WA Coast. Pops have decreased on Thursday with the system departing sooner compared to 24 hours ago. The air mass is also becoming quite dry with PWATS close to 0.35" or 50% of normal. The combination of the dry air, clearing skies, and light winds will lead to cool morning lows each Thursday and Friday. Thursday looks to be the coolest. Here are the latest probabilities for Thursday morning lows of 34F or colder at communities most vulnerable: Winthrop - 10% Republic - 60% Colville - 70% Priest Lake area - 60% Davenport - 20% Deer Park = 25% Friday will feature mostly dry conditions under shortwave ridging. By the weekend and early next week, there remains moderate uncertainty with the forecast with the latest trends toward a flatter ridge over the weekend and increasing threat for showers with an axis of deeper moisture becoming directed inland and weak shortwaves skirting through. Details are far from certain but blending the medium range models has led to increasing PoPs in the mountains. The west to east orientation of the flow pattern suggest little to no precipitation in the lee of the Cascades which is observing one of the largest deficits over the last 60 days. Winds will likely be breezy at times with temperatures running near to warmer than normal. /sb && .AVIATION... 18Z TAFS: Mid to high clouds will continue to filter through the region as the ridge begins to slowly be replaced with the next trough system. VFR conditions will occur through 18z Tuesday. Weather changes arrive late tonight into Tuesday for an increasing chance of showers and thunderstorms over eastern Washington and north Idaho along with breezy winds. FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: There is high confidence for VFR conditions to continue across the TAF sites. Low confidence on showers impacting TAF sites before 18z. ----------------------- 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 52 74 45 62 39 65 / 10 30 10 20 10 0 Coeur d`Alene 51 73 45 59 38 62 / 20 40 30 30 20 0 Pullman 52 71 44 58 37 61 / 20 40 40 10 20 0 Lewiston 57 80 52 66 45 70 / 10 40 60 10 20 0 Colville 45 73 38 61 31 66 / 0 70 40 60 20 10 Sandpoint 48 71 45 56 38 61 / 0 60 60 60 40 10 Kellogg 53 74 48 55 39 59 / 10 40 70 50 40 10 Moses Lake 53 78 43 67 39 72 / 10 20 0 10 0 0 Wenatchee 56 73 45 63 43 69 / 0 10 0 10 0 0 Omak 51 76 42 66 39 71 / 0 20 10 10 0 0 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...None. && $$