Area Forecast Discussion
Issued by NWS Spokane, WA
Issued by NWS Spokane, WA
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146 FXUS66 KOTX 171754 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 1054 AM PDT Tue Sep 17 2024 .SYNOPSIS... Periods of rain will persist over north Idaho and the eastern third of Washington through early Wednesday. Conditions will trend drier toward the end of the work week, then precipitation chances return for the weekend. && .DISCUSSION... Today through Thursday night: Showers will increase along the WA/ID border this morning as the wrap around moisture sets up behind the low that has moved over Nevada. Another low is tracking down along the coast, but most of the moisture will remain on the west side of the Cascades. Rain totals will be less than a quarter inch in the heaviest showers, with, most of the area seeing a tenth or less. Temperatures will cool towards seasonal normals today, with the exception of the Okanogan Valley warming to temperatures similar to yesterday. Winds will remain generally in the 10 to 15 mph range, with occasional gusts to 20 in the Columbia Basin. The chance of showers will continue into the overnight hours, with the low shifting eastward in the early morning hours. A slight chance of showers continues in the Idaho Panhandle, but by early afternoon, the region is anticipated to dry out. Temperatures will continue to be near seasonal normals for Wednesday and Thursday, with dry conditions persisting through the day Thursday as weak ridging builds over the region. /KM Friday to Monday: The Inland NW will be in a progressive west- northwest flow, with a series of weak waves crossing the region starting this weekend. Friday looks mostly dry except for slight showers in the onshore flow near the Cascade crest and over the far northern Panhandle. Some breezy conditions are also in the forecast Friday, with gusts of 15-20 mph. Then shower chance expand some Saturday to Monday. The best chances remain around the mountains Saturday, then increase over a larger portion of the area heading into Saturday night, Sunday and Monday. The deeper Columbia Basin will have the smallest risk and the higher risk will remain in the mountains. Right now these weak systems are not expected to be big precipitation producers, if anything falls. There is still some disagreement in the details of the timing and track of the individual features, but overall models have trended showing most models showing lighter precipitation. Temperatures will be near the slightly below normal. Some patchy frost is possible in some of the sheltered valleys around north- central to northeast WA and the ID Panhandle Saturday morning and even more isolated fashion Sunday morning. There could also be some patchy morning fog in the sheltered valleys and around the bodies of water. /Solveig && .AVIATION... 12Z TAFS: Scattered showers will continue to rotate north up into SE Washington, the Idaho Panhandle, and far eastern reaches of NE Washington through tonight. Showers that form over TAF sites may result in brief visibility reductions to MVFR. With a moist boundary layer and middle to high level clouds thinning overnight, a handful of model soundings are showing a marginal VFR developing around KGEG, KSFF, KCOE, KDEW around 12Z Wednesday morning. FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: Moderate confidence of increasing showers for southeast Washington and north Idaho through tonight. Some models show some localized heavier showers, but confidence of these impacting the TAF sites carries lower confidence. There is low confidence for stratus development around KGEG, KSFF, KCOE, KDEW early Wednesday morning. Despite several model soundings showing this development along with a 40 to 60 percent chance in the High Resolution Ensemble Forecast (HREF) system, the National Blend of Models is giving these areas a zero percent chance. Included a FEW015 at KGEG/KSFF and SCT015 at KCOE to message this potential, but was not confident enough to reduce conditions to MVFR. && .PRELIMINARY POINT TEMPS/POPS... Spokane 73 49 76 49 76 47 / 40 20 10 0 0 0 Coeur d`Alene 71 48 72 48 75 48 / 60 40 20 0 0 0 Pullman 65 45 69 43 73 45 / 60 30 20 0 0 0 Lewiston 74 54 76 53 79 53 / 60 20 10 0 0 0 Colville 77 38 78 39 76 38 / 20 20 10 0 0 0 Sandpoint 70 46 72 45 73 44 / 50 50 20 0 0 0 Kellogg 66 49 67 50 72 49 / 70 60 30 10 0 0 Moses Lake 79 48 79 46 78 46 / 0 10 0 0 0 0 Wenatchee 78 55 80 53 79 53 / 0 0 0 0 0 0 Omak 83 51 82 51 81 48 / 10 10 0 0 0 0 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...None. && $$