FXUS66 KOTX 111137 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 337 AM PST Mon Dec 11 2023 .SYNOPSIS... A couple weak systems pass this week, today and Thursday, with opportunities for light precipitation. Otherwise a ridge of high pressure settles in, leading to several days of low clouds and areas of fog. && .DISCUSSION... Today through Tuesday night: Areas of fog and low clouds, as well as limited precipitation chances, linger. This morning a moist boundary layer and weak warm advection in advance of the next shortwave disturbance is helping to provide low clouds and fog across large portion of eastern WA and ID. Some of the more notable fog, per observations, is found across the Upper Columbia Basin into the West Plains, as well as the higher hills around the Spokane Metro and in some of the mountain valleys north of toward the Canadian border. Ensembles keep the low clouds and fog in place this morning, then at least start to lift the base of the stratus between midday to mid-afternoon. Some even break up the stratus enough to allow partly cloudy to partly sunny conditions near the Cascades through north-central WA. That seems a reasonable possibility as drier air comes in on the backside of the mid-level shortwave dropping in from the west-northwest. Yet throughout the upper Columbia Basin eastward the stratus holds on. The shortwave will provide light rain and snow chances to southeast WA and the ID Panhandle. The best chances for measurable precipitation will be over the central Panhandle through the southern Palouse, Blues and Camas Prairie. Elsewhere, the precipitation is expected to be lighter and may just be found in the form of drizzle. As we go into the afternoon the precipitation potential starts to wane from the northwest and by this evening only the Blues, Camas Prairie and eastern Shoshone county sees lingering light rain and snow chances. Overall snow amounts, if any, are expected to be less than 1 inch, though with some weak instability there could be a localized heavier burst of snow around the central Panhandle mountains. Going into overnight and Tuesday the area generally looks drier. However the stratus deck is expected to expand and lower again, with fog increasing in coverage again. There may be some drizzle and patches of freezing drizzle with the stratus. As Tuesday progresses and the next system approaches the flow turns more easterly, shifting the deeper stratus/low clouds toward the Cascades and north-central WA. Some light snow or rain may be squeezed out in the upslope flow, with the potential near the Cascades, but this too could also be in the form of drizzle or freezing drizzle. At this time impacts are expected to be minor, if any with precipitation amounts not expected to be more than trace amounts of for most. However this will be monitored, especially if the potential for any freezing drizzle looks more likely. /Solveig Wednesday through Thursday night: A couple shortwaves will pass over the region on Wednesday night and Thursday night, bringing a chance of light snowfall over the higher elevations and a mix to the lowlands. Impacts will be minimal with these systems as little snow is expected. Temperatures will remain consistent, with highs in the upper 30s to low 40s, and lows in the mid to upper 20s. With the recent moisture along with the potential for additional moisture, low stratus and fog could hang around in the overnight to morning hours for much of the lower elevations. With overnight lows expected to fall below freezing, freezing fog is also a concern. Friday through Sunday: High pressure will build into the PacNW for the weekend, bringing dry conditions. With the high pressure, fog and freezing fog will continue to be a nuisance in the overnight to morning hours. /KM && .AVIATION... 12Z TAFS: TAF sites are expected to remain impacted by MVFR/IFR conditions over the next 24 hours, with areas of LIFR conditions in the morning and overnight hours. A weak system dropping in from the north today will bring a risk for -ra/-sn or just some drizzle around GEG/SFF/COE/PUW/LWS today, with the potential waning into this afternoon. Drier air coming on the backside of the system will allow for some improvement toward the Okanogan Valley, but elsewhere the main impact will be some slight lift in the stratus through the day before it descends again later this evening into Tuesday morning. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS: There is high confidence of continued restrictions over the region with widespread stratus. Given multiple stratus layers confidence in precise ceilings and visibility is low. There is moderate to high confidence TAF sites will stay in IFR/MVFR conditions through the period. There is low confidence that some VFR conditions could develop near EAT late this afternoon and early evening. ------------------ 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 38 31 38 25 36 28 / 30 10 10 10 0 10 Coeur d'Alene 40 31 39 24 36 27 / 30 10 10 10 0 10 Pullman 40 33 40 26 38 29 / 30 10 10 10 0 10 Lewiston 45 38 45 31 43 32 / 20 10 10 10 0 0 Colville 39 23 36 23 37 25 / 10 0 10 10 0 30 Sandpoint 38 27 37 24 38 26 / 30 0 0 10 0 20 Kellogg 40 33 39 24 41 30 / 50 10 10 0 0 10 Moses Lake 41 32 41 29 39 29 / 10 10 10 10 0 10 Wenatchee 39 31 37 34 37 32 / 10 0 10 10 0 20 Omak 39 29 38 29 38 29 / 10 0 10 10 0 20 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...None. && $$