Marine Weather and Tide Forecast for Moscow, ID

SYNOPSIS
Mountain snow showers continue into Friday. This will bring winter travel conditions over Stevens Pass Thursday night into Friday. A vigorous cold front will bring gusty westerly winds on Sunday. Next week is being monitored for the return of moderate, perhaps heavy mountain snow and windy conditions.

DISCUSSION

...COLD FRONT ON SUNDAY TO BRING WINDY CONDITIONS AND WILL USHER IN COLDER TEMPERATURES WITH LOWERING SNOW LEVELS FOR NEXT WEEK...

Tonight through Sunday: A warm front will move into the Cascades bringing light snow to the Cascades tonight into Monday. Snow levels will start out between 2,000 and 3,000 feet with snowy travel expected over Stevens Pass. Moisture drops precipitously east of the Cascade crest with little to no precipitation expected in Wenatchee to the Okanogan Valley. This will mean that snow impacts will mainly just be confined to travel up and over Stevens Pass with snow accumulations of 2 to 4 inches and only a 5% chance for greater than 4 inches of snow falling at the pass. The warm front will shift across Eastern Washington into the Idaho Panhandle through the day on Friday and continuing on into Friday night and Saturday.
The atmosphere will moisten up through this period with light precipitation falling over the Idaho Panhandle into extreme Eastern Washington by Friday afternoon, but probabilities increasing into Friday night. There is a greater than 80% chance for measurable (> 0.01 inches) of precipitation over the Idaho Panhandle Friday night into Saturday morning. Snow levels will be increasing with the warm front on Friday with precipitation type transitioning from snow to rain in the mountains, which will limit accumulations over Lookout Pass.

Light precipitation will continue in the mountains into Saturday.
Then a vigorous cold front brings the potential for significant impacts due to wind and then moderate to heavy snow later on past this forecast period. Model ensembles are ramping up the wind potential for Sunday though. The ECMWF ensembles shows up to half of the forecast members with 50 mph wind gusts across much of the region. Best potential will be across the exposed areas of the Columbia Basin. Areas more sheltered in the mountains across northeast Washington and into the Northern Panhandle will be less likely see wind gusts up to 50 mph, but there are more trees for these winds to impacts and there is potential for tree damage and isolated power outages to occur.

Sunday night through Thursday: This will be the period where significant snow will be possible over the mountains. Colder temperatures with Sunday's cold front passage will usher in an extended period of colder than average temperatures and snow levels down to valley bottoms. The Inland Northwest will be on the northern, unstable side of jet stream. Model ensembles also indicate a healthy plume of moisture being directed across the Northwest through much of the work week. Precipitation that comes on Monday will be in the post front air mass and generally be confined over the Cascade crest and in the Idaho Panhandle.
Stevens Pass is expected to see moderate snow accumulations with periods of burst of heavy snow possible. There is an 80% chance for 8+ inches of snow for Monday through Monday night at Stevens Pass and a 25% chance for 18 inches. Snow of over a foot will likely be dependent on where a Puget Sound Convergence Zone (PSCZ) setting up. This mesoscale feature can result in very heavy snow with rates of 1-2 inches of snow falling per hour.

Multiple additional weather system will swing through in a moist zonal flow pattern Tuesday through Friday. Strong westerly flow will result in a precipitation shadow in the lee of the Cascades, but this will also result in strong upslope flow with periods of heavy snow across the Cascade crest. Colder temperatures on the unstable side of the jet will also result in higher snow ratios and very well may result in significant travel impacts over the Cascades. The other mountain pass that may see heavy snow is Lookout Pass with the period of Wednesday through Friday being the best potential for winter travel impacts. Valleys will see the potential for snow as well, but much more uncertainty and most likely would be for the overnight hours as snow has a hard time accumulating on roads in March with the higher sun angle. /SVH

AVIATION
18Z TAFS: The Inland Northwest will be under modestly unstable northwest flow today. Winds will pick up through the rest of this morning into the afternoon with gusts up to between 20-30 kts out of the west and southwest. Shallow instability near the surface will result in developing cumulus and stratocumulus clouds. Cloud bases will be between 2-4 kft agl. through 20-22Z with MVFR ceilings mainly for KPUW and KCOE and potentially as as far west as KGEG. Ceilings will lift with VFR conditions by 22Z today. Cumulus clouds will bring light showers to the region with a 30-50% chance of impacting KPUW and KCOE terminals. A warm front begins to move in Friday morning with increase and thickening mid level clouds cover. Low stratus is also expected to develop between 10-15Z at or near KPUW/KGEG/KSFF- KCOE with MVFR conditions expected.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: Moderate confidence of MVFR ceilings at KPUW and high confidence at KCOE for this morning before ceilings lift in the afternoon. Moderate to high confidence for a low stratus deck to form between KGEG/KSFF- KCOE/KPUW with MVFR conditions after 10Z Friday morning. There is a 50% chance that this stratus cover will bring a broken ceiling of between 1-3 kft agl. at KGEG and a greater than 50% chance for KSFF/KCOE/KPUW. /SVH

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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 32 46 40 56 43 56 / 0 20 30 10 10 20 Coeur d'Alene 32 44 39 52 43 54 / 10 30 60 40 20 50 Pullman 32 43 39 53 42 54 / 10 40 50 30 10 40 Lewiston 35 49 43 61 44 61 / 10 20 30 10 0 20 Colville 30 49 35 54 40 58 / 0 10 30 10 10 30 Sandpoint 32 42 37 47 41 51 / 10 30 70 60 40 80 Kellogg 31 40 38 48 43 49 / 40 70 80 80 40 70 Moses Lake 34 57 41 62 43 63 / 10 30 20 0 0 0 Wenatchee 37 56 44 61 44 59 / 10 20 20 0 10 30 Omak 34 51 39 58 41 59 / 10 10 20 0 10 20

OTX WATCHES/WARNINGS/ADVISORIES
WA...None.
ID...None.