Area Forecast Discussion
Issued by NWS Spokane, WA
Issued by NWS Spokane, WA
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584 FXUS66 KOTX 222100 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 200 PM PDT Sun Sep 22 2024 .SYNOPSIS... A weak weather system will deliver increasing clouds and warmer overnight low temperatures for tonight. A ridge of high pressure will deliver above normal temperatures Monday and Tuesday. A more active pattern is expected toward midweek and beyond, with the potential for breezy conditions and showers. Temperatures return to near normal by Thursday. && .DISCUSSION... Tonight through Tuesday Night: A warm front will spread increasing mid and high clouds over the region tonight into Monday morning. The bulk of the lift will pass north of the Canadian border with the chance of rain limited to mainly the Cascade crest. Cloud cover will help moderate lows tonight with lows mainly in the mid 40s to mid 50s. Upper level high pressure moves over the region on Tuesday with the ridge axis pushing into eastern Idaho and western Montana in the afternoon. This will result in warmer southwest flow with 850mb temps climbing to near 20C supporting high temperatures warming into the 80s for most towns. Wednesday and Wednesday Night: The ridge pushes east into the midwest while a closed low in the Gulf of Alaska sends a cold front across the Inland Northwest late Wednesday. The front reaches the Cascades late in the afternoon before swinging into Eastern WA/N Idaho Wednesday evening. This is a stronger front (typical for late September) with a 100 kt south to north upper jet paralleling the front. Yet the initially dry low levels and quick movement will result in the best chances for rain along the Cascade crest (70-80 percent), and the Idaho Panhandle (50-60 percent). The front also will bring a burst of cold advection supporting breezy to windy conditions, especially across the Wenatchee area, Columbia Basin, West Plains, and Palouse with 30-35 MPH gusts expected, locally to 40 MPH. Given the dry conditions and time of year these winds will likely pick up patchy blowing dust for the Columbia Basin. Elevated instability along and ahead of the front over the Blue Mountains into the Central Panhandle Mountains will lead to a 20% chance of thunderstorms Wednesday evening as well. Thursday through Sunday: After a quiet Thursday, ensembles show another system passing into British Columbia on Friday sending another cold front across the region. This time the jet is zonal (west to east), with a noteable dry slot moving across the region. Another round of breezy to locally windy conditions is expected. Ensembles show a larger spread in wind gusts for the region, but currently 80-90% of the solutions favor winds below wind advisory criteria. Drier air behind the front will lead to colder overnight lows next weekend, with the main frost potential for areas that just had a frost this past weekend. The winds Wednesday and Friday will lead to elevated fire weather conditions across the Columbia Basin, and the East Slope Cascade valleys. Relative humidity looks to stay above critical thresholds. JW && .AVIATION... 18Z TAFS: VFR conditions. Bands of mid and high clouds will move over the region, thickening this afternoon into tonight. Some showers possible in the Cascades late this afternoon into tonight. Gusty winds to 15kts or so near Cascade gaps into the Columbia Basin by late afternoon to early evening, including in vcnty of EAT, MWH and GEG. FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence for VFR conditions at all TAF sites. Low confidence sprinkles at TAF sites overnight. && .PRELIMINARY POINT TEMPS/POPS... Spokane 52 78 51 86 57 85 / 0 10 0 0 0 20 Coeur d`Alene 50 75 51 84 56 84 / 0 10 0 0 0 20 Pullman 49 72 49 82 55 83 / 0 0 0 0 0 20 Lewiston 56 80 56 89 61 89 / 0 0 0 0 0 10 Colville 46 78 43 83 45 83 / 0 10 0 0 0 10 Sandpoint 47 72 47 79 52 80 / 0 10 0 0 0 20 Kellogg 49 70 53 81 60 80 / 0 10 0 0 0 10 Moses Lake 55 82 53 86 55 84 / 0 10 0 0 0 10 Wenatchee 60 82 59 84 61 80 / 10 10 0 0 0 20 Omak 55 85 56 87 58 84 / 10 10 0 0 0 30 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...None. && $$