Area Forecast Discussion
Issued by NWS Spokane, WA

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000 FXUS66 KOTX 251122 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 422 AM PDT Wed May 25 2022 .SYNOPSIS... Outside a few sprinkles today, look for warming temperatures and dry conditions into Thursday afternoon. Afternoon highs by Thursday will reach the 70s and lower 80s. The threat for showers and thunderstorms returns Thursday afternoon and evening. A few storms in the lower Idaho Panhandle could be strong. Cool and unsettled conditions return for Memorial Day weekend. && .DISCUSSION... Today and tonight: A flat ridge of high pressure has found its way into the Northwest and will deliver a relatively dry and mild weather pattern over the next 36 hours. An axis of subtropical moisture remains draped over the ridge and we are getting reports of light rain at times but this activity has been very light with amounts generally between a trace and 0.01". There is not much forcing to squeeze out this moisture other than a 700mb warm front which looks to fall apart as the day wears on. Consequently, any chance for light rain will migrate into the mountains where terrain will intercept the moisture at times. Majority of the Basin and lee of the Cascades will experience high overcast. The air mass will warm an additional 2 Celsius around 850mb which will equate to 4 to 6 degrees of warming at the surface pushing afternoon highs into the upper 60s to lower 70s. There is about a 50% chance Spokane International reaches 70F. We will continue to experiencing moistening and warming of the air mass overnight which will result in mild temperatures compared to what we have become accustomed to over the last month. Overnight lows will remain in the 40s for most locations with our warmer communities in the lower Basin and Hwy 97 corridor lingering in the lower 50s. ...STRONG TO SEVERE THUNDERSTORMS POSSIBLE ON THE CAMAS PRAIRIE THURSDAY AFTERNOON AND EARLY EVENING... Thursday and Thursday night: A trough of low pressure approaches the coast Thursday and swings inland Thursday night. Midlevel flow will buckle to the southwest further warming and moistening the air mass over the Inland Northwest. It may even feel muggy to some folks across the eastern third of Washington and North Idaho as dewpoints climb into the 50s. Much of the day will be quiet with dry conditions. Temperatures will continue to warm with nearly all valleys reaching the 70s and a 50-60% chance for Moses Lake and Lewiston to hit the lower 80s. NBM has nearly a 100% chance that Spokane International will finally hit 70F on Thursday. Our concerns for impactful weather will come late Thursday afternoon into Thursday night. The combination of strong heating and increasing moisture over the lower Idaho Panhandle and extreme southeastern WA will result in exceptionally high CAPE values near 1000 J/kg or higher Meanwhile, a strengthening 500mb jet will lead to effective shear around 45kts. So the thermodynamic ingredients will be in place for strong to severe storms but as with most of these cases, there will be cin (convective inhibition) to overcome or we will need a kicker to get storms going. Now that we have access to CAM (convective allowing models) we are getting a sneak peak at what these models are showing and seeing a lot of support from these hi-res models that the high terrain over Northeastern Oregon will be that factor with cells developing during peak heating and tracking northeast toward the Camas Prairie and extreme southeastern WA Thursday starting roughly 5PM-8PM. At this time, a majority of models keep the beefiest cells over Lewis County and points south but a few, such as the 3KM NAM suggest some of these stronger cells expand further north toward Lewiston and northeaster Nez Perce County. I would say this carries low confidence at this time but something we will need to monitor. Higher confidence would be for impactful storms around Kamiah and Winchester. There will be very high moisture content in this air mass but storms should also be tracking swiftly to the northeast. As such torrential rains will be a concern with any storms along with large hail and damaging wind gusts. There is also instability noted further north into Spokane and the Northern Idaho Panhandle as the afternoon heats up but this area will most likely experience a lot of CIN and lack a "kicker" during peak heating. The kicker that we will be waiting for is the 850-700mb cold front. This front will cross into Central WA Thursday afternoon (mainly just bringing showers to Central WA) then slowly work its way toward the Washington-Idaho closer to 8PM or around sunset. There will be some lingering instability at this time but not as juicy as if it were to arrive earlier. The air mass will contain very high moisture content so I do anticipate bands of heavy showers and some thunderstorms but the main concerns will be heavy downpours, gusty winds, and lightning strikes. There are some differences with the speed of the front tracking through Idaho. Given the slowest solutions, some areas could pick up well over a half an inch of rainfall. A quicker frontal passage would result in amounts closer to a quarter of an inch or lower. Right now, looks like the Central Panhandle Mountains in Idaho southward toward the Camas Prairie stand the best shot of rainfall amounts over half an inch and locally near an inch. This will need to be monitored for localized flooding issues. /sb Friday to Tuesday: The Inland Northwest moves into a cooler, wetter pattern as a trough settles into the region. A cold front pushes east early Friday, while an upper shortwave comes on its heels. This feature coupled with 200-500 J/kg of CAPE will bring a chance of showers and thunderstorms to much of the region. The best chances will be over the east third of WA and ID. Ensembles are showing about a 70-90% chance of wetting rains (>=0.10) in these latter areas. The system will also be accompanied by breezy to windy conditions. Ensembles here show a high chance of wind gusts over 25 mph at near 80-99% and around a 10-30% chance of wind gusts near 40 mph or higher from the Upper Columbia Basin to the Palouse/Spokane area. Areas across the Columbia Basin to the West Plains could see some patchy blowing dust but confidence remains low. Going into Saturday the area looks somewhat drier, with the primary shower chances around the mountains and far southeast WA and the lower ID Panhandle. The next wave moves in between Saturday night and Sunday, revitalizing precipitation chances across the region. Compared to this time yesterday models track the core of this system a bit further south. So there remains some run-to-run inconsistency. Ensembles show about 40-70% chance of wetting rains across southeast WA and the southern ID Panhandle, with about 10-50% elsewhere (highest around the mountains). This coincides with the shift of the core of the system farther southeast. Monday and Tuesday the upper trough axis starts to shift east, putting our region in a north to northwest flow. There is enough instability to keep showers in the forecast, particularly over the mountains and southeast CWA. /Cote` && .AVIATION...
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12Z TAFS: A warm front continues to slowly lift through the region this morning resulting in ceilings down to between 6-10 kft and spotty sprinkles. As the warm front lifts northward...afternoon heating will bring a resurgence of flat cumulus and potential for ceilings around 6kft. Fair cumulus will dissipate after 00z leaving mainly high clouds at or above 15kft. Local wind gusts 20-25 mph expected across the Basin, Palouse and West Plains today, otherwise mainly light winds. /sb
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&& .PRELIMINARY POINT TEMPS/POPS... Spokane 69 49 76 53 66 43 / 10 10 0 50 50 10 Coeur d`Alene 66 48 76 52 64 43 / 20 10 0 70 70 20 Pullman 69 50 76 52 62 45 / 0 0 0 70 60 20 Lewiston 78 55 82 58 69 51 / 0 0 10 80 70 30 Colville 71 47 76 50 68 40 / 10 10 10 30 60 10 Sandpoint 62 47 72 51 61 42 / 20 10 10 70 80 30 Kellogg 61 50 74 53 60 45 / 40 10 0 80 80 30 Moses Lake 77 49 80 53 72 43 / 0 0 0 10 10 0 Wenatchee 74 53 76 54 68 46 / 0 0 10 30 30 10 Omak 75 51 76 52 72 43 / 10 0 10 30 30 0 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...None. && $$

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