FXUS66 KOTX 190439 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 939 PM PDT Wed Sep 18 2024 .SYNOPSIS... Weather will trend drier toward the end of the work week, then light rain chances mainly for the mountains Sunday into Monday. A ridge of high pressure will deliver above normal temperatures early next week. && .DISCUSSION... Wednesday night through Friday: The Inland Northwest is currently sitting under a broad north to northwest flow aloft as an upper level low moves south across California and another one moves northeast across eastern Montana and western North Dakota. Weak ridging over the Inland Northwest tonight into early Thursday will allow temperatures into the 70s across much of the region and low 80s along the lower valleys in central Washington, the Columbia Basin, and the L-C Valley. A system moving across British Columbia Thursday afternoon into Friday will bring a dry and weak cold front across the Inland Northwest Thursday night. Increased onshore flow ahead of the front will bring breezy winds through the Cascade gaps Thursday evening. The NBM is indicating the Inland Northwest to remain dry with this, with only a 20 percent chance for 0.01 inches of precipitation at the Cascade crest and far northeast Idaho Panhandle. Behind the front, temperatures will cool by a couple degrees and winds will become breezy from the north through the Okanogan Valley, upper Columbia Basin, and the lee of the Blue mountains Friday morning and afternoon. Saturday through Wednesday: Drier air moving into the region within a northwest flow aloft into the Inland Northwest as the upper level trough moves eastward across Canada will keep skies clear overnight. A handful of models are suggesting temperatures dropping into the low 30s across the northeast Washington valleys Saturday morning.The National Blend of Models is giving Colville a 40 percent chance, Chewelah a 30 percent chance, and Deer Park a 20 percent chance for temperatures of 32 or below Saturday morning. Those still tending to a garden across northeast Washington may want to take precaution. Models have significantly backed off on the idea of precipitation on Sunday with an upper level ridge building from the south deflecting most of the precipitation chances west of the Cascades and north into Canada. The NBM continues to carry a 15 to 20 percent chance for precipitation across the Cascades, the northern mountains, and the northern Idaho Panhandle, but I would not be surprised if this continues to trend lower. A modest plume of moisture with PWATs increasing to over 150 percent of normal accompanying this system will bring an increase in clouds for Sunday and Monday across eastern Washington and north Idaho. As the ridge builds from the south, temperatures across the Inland Northwest will warm into the 70s and low 80s for Tuesday and Wednesday. Whether this ridge stays parked over the region into the latter half of the week is uncertain as about 40 to 50 percent of ensembles between Wednesday and Thursday show a cold front moving through the Pacific Northwest. This would bring cooler, possibly wetter, and breezier conditions. There is disagreement within this subset of ensemble members on the strength and speed of this system. The other 50 to 60 percent of ensembles keep in place with warm and dry weather continuing. /vmt && .AVIATION... 06Z TAFS: VFR conditions are forecast for the TAF sites through 06z Friday. Patchy valley fog may form between 12-16z near water sources in NE WA/N Idaho but confidence of this impacting any of the TAF sites is low given still large temperature/dew point spreads this evening. A weather system passing into British Columbia will enhance the winds Thursday afternoon across the Wenatchee area, Columbia Basin, into the Spokane area and Palouse with breezy west to southwest winds. Wind gusts to near 20 kts are forecast but could be locally stronger especially around KEAT. FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence for VFR conditions to continue for the TAF sites. JW && .PRELIMINARY POINT TEMPS/POPS... Spokane 49 75 47 72 43 71 / 0 0 0 0 0 0 Coeur d'Alene 48 74 47 69 43 70 / 0 0 0 0 0 0 Pullman 44 72 45 65 39 67 / 0 0 0 0 0 0 Lewiston 54 81 53 74 50 75 / 0 0 0 0 0 0 Colville 39 75 36 71 32 70 / 0 0 0 0 0 0 Sandpoint 45 71 43 68 36 68 / 0 0 0 10 0 0 Kellogg 50 72 48 65 45 66 / 0 0 0 0 0 0 Moses Lake 46 79 46 74 42 73 / 0 0 0 0 0 0 Wenatchee 54 79 54 72 48 74 / 0 0 0 0 0 0 Omak 51 81 47 74 46 75 / 0 0 0 0 0 0 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...None. && $$