Peck, ID 83545 Weather

Key messages

- Valley rain and mountain snow at times through the week.

- Winter travel conditions in the Cascades through Wednesday, especially over Stevens and Washington Passes.

Synopsis

Valley rain and mountain snow is forecast at times through the week with the highest snow amounts in the Cascades through Wednesday.

Discussion

Wednesday through Thursday: A deep closed low dropping out of southern British Columbia will bring cooler temperatures to the region, along with increasing showers on Wednesday. This is due to increased lift, as well as unstable conditions as 500mb temperatures plunge -30C over the northern half of Washington into the North Idaho Panhandle. This combined with lower level upslope flow from west- southwest winds at 850mb into the Cascade crest, and mountains of Northeast Washington and the North ID Panhandle will produce several inches of snow. Bands of convergence into the Cascades also has the potential to produce brief periods of heavier snow with HREF showing around a 30-40 percent chance of 1 inch per hour snow rates. A Winter Weather Advisory remains in place for elevations above 3000 feet in the Cascades through 5 PM Wednesday with the highest amounts expected over Stevens and Washington Passes. Wednesday Night into Thursday as the closed low drops south to off the WA coast the flow turns southwest. Drier air coming into the region in the mid levels will result in a decrease in the intensity and coverage of showers, but enough moisture lingers over the northern mountains and Cascades for additional light rain and mountain snow amounts. Below are the NBM chances for various snow thresholds being reached for the mountain passes from 5 PM Tuesday to 5 PM Thursday:

Mountain Pass 2+ inches 4+ inches 6+ inches 8+ inches Stevens Pass 100% 95% 70% 50% Washington Pass 100% 75% 30% 5% Sherman Pass 50% 10% 0% 0% Lookout Pass 90% 50% 10% 5%

Friday through Tuesday: The influence of the upper low continues Friday and Saturday as another wave associated with the low passes through for more cool and showery conditions with mountain snow showers, and a rain/snow mix in the valleys. On Sunday the low starts to push out and is replaced by an upper ridge on Monday and Tuesday bringing dry weather and slightly warmer temperatures.

Aviation

12Z TAFS: Rain and mountain snow showers will continue today as a low pressure system wobbles over the area. Mid-level westerly flow will focus the highest activity in the Cascades, eastern third of WA, and the ID Panhandle. MVFR ceilings can be seen on satellite expanding over Northeast WA and North ID including at KGEG/KSFF/KCOE. Expect MVFR conditions to persist over these terminals through the morning and early afternoon before improving through the evening. Southwest winds with gusts of 15-25 kts will continue across the region through this morning.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence that downslope flow off area terrain keeps conditions VFR at KEAT/KMWH/KLWS. Moderate to high confidence in MVFR conditions continuing through early afternoon for KGEG/KSFF/KCOE.

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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 48 34 50 36 50 34 / 90 50 0 0 10 0 Coeur d'Alene 44 34 49 34 50 33 / 100 70 20 0 10 10 Pullman 46 35 49 35 48 34 / 100 40 0 0 10 20 Lewiston 53 38 53 39 53 37 / 50 40 10 0 0 20 Colville 46 34 47 33 48 30 / 90 40 20 10 20 0 Sandpoint 41 34 46 34 46 32 / 100 90 20 0 10 0 Kellogg 41 33 47 33 48 35 / 100 80 20 0 10 10 Moses Lake 54 34 52 35 51 32 / 20 10 0 0 10 0 Wenatchee 51 35 47 37 49 35 / 10 0 0 40 50 0 Omak 49 34 48 35 47 33 / 70 10 10 10 50 10

Watches, warnings and advisories

WA: Winter Weather Advisory until 5 PM PDT this afternoon for Western Chelan County-Western Okanogan County. ID: None.