FXUS66 KOTX 182253 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 253 PM PST Wed Dec 18 2024 .SYNOPSIS... A ridge of high pressure will result in a drying trend and calmer winds through Friday. Unsettled weather will return this weekend and continue into next week. Mild temperatures will result in precipitation falling primarily as valley rain and mountain snow. && .DISCUSSION... KEY POINTS: * Winds will decrease through this evening and become light overnight. * Mild temperatures and dry over much of the Inland Northwest through Friday. * Unsettled weather this weekend into next week with valley rain and mountain snow returning. Tonight through Friday night: High pressure will begin to build in over the region tonight. The pressure gradient producing the gusty winds across the region will relax and will see winds calming down overnight. A warm front will approach off of the eastern Pacific and this will form thin high clouds over eastern Washington. What we see in the way of low level clouds is more uncertain as our winds today has mixed a significant amount of drier air down into the boundary layer. This should limit the stratus cover that develops, and the 12Z NAM guidance in particular looks to be a bit overdone. The approaching warm front will increase the easterly flow in the boundary layer though for Thursday, and will likely start to see low clouds forming near the Cascades as that moisture pools up against the east slopes. Moisture with this front will be limited. There is a 70 percent chance for precipitation at the Cascade crest Thursday night. Snow levels will be above pass level though with Stevens Pass expected to see rain. Those probabilities drop significantly away from the Cascades with a 30 percent chance for precipitation over the northern mountains. Precipitation type looks to be a rain/snow mix in the valleys and light snow in the mountains. Any snow that falls though will be very light and isn't expected to result in impacts. Another weak shortwave disturbance will push across the Cascades and brush the northern mountain zones Friday into Friday night. This one will look very similar to the one Thursday night. Little in the way of moisture with it, and the building ridge over the region will direct the bulk of it and associated dynamics north into BC. Temperatures will be mild and above normal for mid December. Expect high temperatures in the upper 30s and 40s and overnight lows dropping into the mid 20s to lower 30s. These temperatures will generally be 8-12 degrees above normal. /SVH Saturday through Wednesday: Several disturbances will push through the Inland Northwest and lead to chances for precip through much of the period. However, enough warm air remains that rain will be the primary precip type below 3500 feet, with snow generally confined to the mountains. Not looking like a good recipe for a white Christmas for most communities, but certainly something we'll be watching over the coming days. Above normal highs for the period typically in the upper 30s to low 40s, with lows in the 20s to low 30s. /KD && .AVIATION... 00Z TAFS: Gusty westerly winds will gradually decrease through this evening as a cold front continues to rapidly push away across Montana. Moisture at upper levels will result in an expanding cirrus stratus cloud deck east of the Cascades. The combination of high clouds and wind into at least the early part of the overnight hours should limit the amount of low level clouds that we see tonight. Patchy fog is expected in the northern mountain valleys, otherwise conditions are expected to remain VFR. An easterly gradient will develop on Thursday and pool boundary layer moisture up against the east slopes of the Cascades where low stratus is expected to develop at some point either by the afternoon on evening on Thursday. FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence in VFR this evening into the overnight hours. Confidence is moderate for stratus to develop over the northern to western basin and into the Cascades by mid morning into the afternoon Thursday. /SVH ----------------------- 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 30 39 33 43 32 42 / 0 0 10 0 10 30 Coeur d'Alene 29 39 32 44 32 42 / 0 0 10 0 10 30 Pullman 31 40 34 46 34 44 / 0 0 0 0 0 40 Lewiston 33 46 37 50 36 47 / 0 0 0 0 0 30 Colville 24 36 30 39 29 39 / 0 10 30 0 20 30 Sandpoint 28 36 32 41 31 39 / 0 10 20 10 20 20 Kellogg 31 41 33 46 34 44 / 0 0 10 0 10 30 Moses Lake 30 42 33 44 33 42 / 0 10 10 0 0 50 Wenatchee 31 37 32 40 33 39 / 0 10 10 0 0 40 Omak 27 37 32 40 32 39 / 0 10 20 0 10 30 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...None. && $$