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FXUS66 KOTX 280454 AFDOTX

Area Forecast Discussion National Weather Service Spokane WA 954 PM PDT Sat Apr 27 2024

SYNOPSIS
The remainder of the weekend and early next week will feature showery weather over the mountains with seasonal like temperatures. Sunday and Monday have the potential to be windy with the passage of a frontal system. This system will also bring snow to the Cascade mountain passes Sunday night and Monday morning. Temperatures begin to warm mid next week onward, but showers remain in the forecast as well.

DISCUSSION
Tonight through Monday Night: Trough moving through the region is producing scattered rain showers with a few lightning strikes this afternoon. The cores are very small, with brief heavy rain possible under the tiny cores and some graupel. The main area is northeast WA and the ID Panhandle. These showers will continue to move northeast through the afternoon and evening hours. Showers will diminish after sunset, however isolated showers will be possible through the night with the trough exiting.

Sunday a stronger trough approaches the area with showers again.
Instability isn't as good Sunday, and only have mention of a 15% chance of thunderstorms for northern Pend Oreille county and the north ID Panhandle Sandpoint area northward in the afternoon.

South to southwest winds will increase Sunday afternoon with over a 90% chance of sustained winds over 20 mph across areas south of Omak onto the Waterville Plateau and a 50% chance across portions of the Columbia Basin and onto the West Plains and western Palouse.
There is about a 10% chance of blowing dust in the Columbia Basin.
Confidence is low and therefore do not have it mentioned in the forecast at this time.

As the trough moves onshore Sunday night snow levels will begin to lower. There is a 90% chance of 3 inches of snow over Stevens Pass Sunday night and Monday morning and a 50% chance of 5 inches.
Have decided to issue a winter weather advisory above 3500 feet for Stevens Pass and the Holden Village area. Snow will start during the evening but begin to accumulate a couple hours after sunset. The HRRR only goes till 12Z Monday, but at 12Z Monday (5am) it is showing a 40% chance of an inch an hour over Stevens Pass. By mid to late morning, it will become more difficult for snow to accumulate on the roads given the sun angle and spring time temps. Snow will continue to fall through Monday night, though accumulations on roads will be minor.

Southwest to west winds pick up again on Monday. The same area mentioned above will see high probabilities of sustain wind speeds 20 mph or greater, and gusts to 30 mph. Given stronger gusts Monday compared to Sunday where dust tends to form, have kept the patchy blowing dust mentioned across portions of the Columbia Basin.

The trough moves into the region Monday afternoon which will bring more widespread showers. Colder 500 mb temps will create enough instability for a 20% chance of thunderstorms for most of eastern Washington and the ID Panhandle. Given the stronger westerly winds have shadowed out the Wenatchee and Moses Lake area in the afternoon. /Nisbet

Tuesday through Friday: Tuesday will be another day of unsettled conditions with showers and isolated thunderstorms over the Cascades, ID Panhandle, and far eastern WA. Winds will decrease through the day on Tuesday from what they were on Monday, but will still be a bit breezy with gusts of 20 to 25 mph.

Most of the region will see temperatures drop near freezing Tuesday night, and a few locations in the mountain valleys and the northern Basin may drop below freezing. Wednesday will be similar to Tuesday with showers and breezy afternoon winds, though the showers on Wednesday will be more limited to the Cascade Crest and mountains of Shoshone County.

Heading into the second half of the week, we start to see significant divergence in model solutions. Around 60 percent of models suggest a ridge will move in, taking the place of the trough that will be over us through the first half of the week, and warming our temperatures back into the 60s by next weekend. The other 40 percent of ensemble members want to keep us in a troughing pattern, which would result in temperatures staying in the 50s through the end of the week. /Fewkes

AVIATION
06Z TAFS: Showers have decreased this evening, with any remaining precip generally limited to far northern ID. Chances for showers increase again after 15Z Sunday. Winds pick up after sunrise Sunday morning and become gusty after 22Z for most TAF locations.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: There is a threat again for scattered to broken MVFR stratus developing Sunday morning 12-18Z between Pullman and Spokane. This comes with low confidence to impact the terminals but is certainly something to monitor.

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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 39 58 39 51 33 53 / 40 20 10 70 10 20 Coeur d'Alene 40 54 38 47 31 50 / 40 50 40 90 20 30 Pullman 39 55 37 48 31 50 / 10 20 30 80 30 50 Lewiston 44 64 44 55 37 57 / 10 10 30 70 20 30 Colville 33 58 34 51 26 52 / 70 30 30 80 20 30 Sandpoint 40 52 38 47 32 47 / 80 70 60 90 40 60 Kellogg 42 51 39 44 33 45 / 40 70 60 90 50 70 Moses Lake 39 63 39 59 34 60 / 0 10 0 20 0 10 Wenatchee 42 60 40 55 37 57 / 10 10 10 20 0 10 Omak 39 63 37 57 32 60 / 10 10 10 30 0 10

OTX WATCHES/WARNINGS/ADVISORIES
ID...None.
WA...Winter Weather Advisory from 11 PM Sunday to 11 AM PDT Monday for Western Chelan County.

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