Area Forecast Discussion
Issued by NWS Spokane, WA
Issued by NWS Spokane, WA
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786 FXUS66 KOTX 061807 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 1107 AM PDT Mon May 6 2024 .SYNOPSIS... Expect cool, windy, and showery conditions for the start of the work week as a trough of low pressure remains over the Inland NW. Then a ridge of high pressure builds into the region, giving way to warmer and drier weather by midweek that continues into the weekend. Next weekend has the potential to deliver our warmest temperatures of the spring so far. && .DISCUSSION... Today and Tonight: In the wake of the departing area of low pressure, the band of rain shifts slowly east and exits eastern WA early this morning and most of north ID by late morning. Gusty drier westerly winds in central WA are expected to expand east and become widespread across the Columbia Basin, Palouse, and West Plains by afternoon. Anticipate wind gusts of 30 to 40 mph. The Inland NW will be under the influence of a broad upper level trough today. With cooling aloft, instability increases with surface based capes from 100 to 300 J/kg from southeast WA into north ID. This would support a 10-15% chance of thunderstorms embedded in the showers. With the windy synoptic winds, any thunderstorm downdrafts could have locally higher gusts. Small hail and occasional lightning would be additional concerns along with brief downpours. The Storm Prediction Center highlights the best chances for convection across the Palouse, LC Valley and Camas Prairie this afternoon and evening. Snow levels near 4K ft would support snow showers in the higher mountains passes, especially Stevens and Lookout Passes although the metro model suggests that road temperatures may limit snow accumulations on the road surfaces. It will be a cool day with daytime highs topping out in the 50s to lower 60s. The showers decrease in the evening, although gusty winds continue in the lee of the Cascades and Palouse. Overnight lows dip into the mid 30s to lower 40s. Pockets of frost will be limited and mainly in sheltered northern valleys where the growing season is slower to start. Tuesday and Tuesday night: Anticipate subtle changes. The upper level trough shifts east as a ridge of high pressure builds in the eastern Pacific. This sets up a drier northerly flow across central WA. The cooler temperatures aloft support diurnal convection and lingering moisture nudged eastward into north Idaho with the threat of rain and mountain snow showers. Thunderstorm chances will be minimal (less than 5%) with merely a stray lightning strike possible. It will be another windy day, although the direction shifts to northwest to north which enhances stronger gusts down the Okanogan Valley, across the Waterville Plateau and Columbia Basin with gusts of 30 to 40 mph. It will be drier as well with a decrease of cloud cover. Daytime temperatures look to be a couple degrees higher than Monday, although still cool for early May. /rfox. Wednesday through Sunday: Ensembles remain in agreement as far as advertising a dry ridging pattern with a warming trend through this period. An exception will be over portions of North Idaho where some minor chances of precipitation linger Wednesday, otherwise positively tilted flopover ridging shows amplification and orientation to favor surface winds from the north and northeast starting Wednesday night and continuing on into about Friday. After Friday the ridge looks like it flattens out some as disturbances overtop it, however their only impacts will be limited to allowing the surface winds to fluctuate a bit more in direction and intensity over the weekend. /Pelatti && .AVIATION... 18Z TAFS: Our band of rain over north Idaho tied to a weakening cold front has largely dissipated this morning. By 19-21z daytime warming will lead to scattered convective showers across eastern Washington. Showers will move east around 30kts into the Spokane, Coeur d`Alene, Pullman, and Lewiston air spaces between 21-02z. Smaller airports like Colville, Sandpoint, Bonners Ferry, and Kellogg as well. A few of the stronger cells this afternoon will be capable of lightning and pea hail. It will be a typical windy day for April with westerly wind gusts in the range of 20-30 kts. /GKoch FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: Amendments may be necessary to improve the timing of showers this afternoon. Overall the thunderstorm threat is low. The probability for lightning at GEG, SFF, COE, PUW, and LWS is less than 20 percent. Lightning headed in the direction of these airports will be handled through short-term amendments. /GKoch ----------------------- 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 57 35 59 37 64 39 / 40 10 10 0 0 0 Coeur d`Alene 53 35 56 37 59 39 / 60 30 20 10 10 0 Pullman 52 34 52 35 56 37 / 40 20 10 0 10 0 Lewiston 60 40 60 41 62 42 / 40 20 10 0 10 0 Colville 59 34 60 36 68 37 / 30 20 10 0 0 0 Sandpoint 52 36 53 38 58 40 / 50 30 30 20 20 0 Kellogg 49 35 49 37 55 40 / 70 50 50 20 20 0 Moses Lake 62 38 64 37 70 41 / 10 10 0 0 0 0 Wenatchee 59 40 59 40 69 46 / 10 0 0 0 0 0 Omak 64 36 66 38 72 44 / 10 10 0 0 0 0 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...None. && $$