Area Forecast Discussion
Issued by NWS Spokane, WA
Issued by NWS Spokane, WA
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674 FXUS66 KOTX 151015 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 315 AM PDT Wed May 15 2024 .SYNOPSIS... An upper level ridge will rebound through Wednesday with temperatures above normal and breezy winds across central Washington. A cold front will move through the region on Thursday, bringing widespread breezy to gusty winds Thursday afternoon through Friday, mountain precipitation, and cooler temperatures. Unsettled weather looks to continue into the weekend && .DISCUSSION... Wednesday: An upper level ridge remains over the region today but will begin to flatten this evening as an upper level low moves southeastward across British Columbia. High clouds associated with this system are streaming across the Inland Northwest under a strong northwest flow aloft and will filter the sunshine through the day. A strong west- northwest oriented upper level jet on the south side of this low will be directed across southern British Columbia Wednesday afternoon through the evening. These strong upper level winds combined with continued onshore low level flow tightening the cross-Cascade pressure gradient will promote another afternoon of gusty winds through the Cascade gaps and central Washington. Sustained winds of 20 to 30 mph and wind gusts of 30 to 45 mph will be capable of blowing around any unsecured lightweight objects. ...Widespread breezy to gusty winds Thursday and Friday... Thursday: A cold front will push through the region Thursday evening. This will be late enough in the day where temperatures will be able to warm into the upper 70s and low 80s for one more day. The biggest concern with this front will be the winds. Winds will begin to pick up ahead of the front Thursday afternoon and peak with the cold front passage as strong winds aloft mix down to the surface. The strongest winds will be felt across the lee of the Cascades in the late afternoon into evening hours with sustained winds near 30 mph and gusts of 45 to 50 mph for the Wenatchee Area, Waterville Plateau, and Moses Lake Area. Areas across the Waterville Plateau and the northern Columbia Basin have a 50-60% chance for wind gusts over 50 mph on Thursday. These strong winds will increase the potential for strong cross winds on north-south facing highways and reduced visibility due to blowing dust near recently worked fields. Further east into the Spokane area sustained west winds of 20 to 30 mph with gusts up to 45 mph are expected. This front will be mostly dry as limited moisture and the strong zonal flow aloft keep the best chances for light precipitation across Cascade crest and the higher elevations of northeast Washington and north Idaho. Snow levels will drop to 4000-4500 feet with very light snow for the high mountains. /vmt Friday: Post frontal winds will continue through Friday afternoon as low pressure deepens over the Dakotas and the prairies of south central Canada. While Thursday`s winds look stronger during the frontal passage, Friday will continue to be quite windy. Sustained west winds of 20 to 25 mph are common within the ECMWF ensemble membership. Gusts of 30 to 40 mph are likely from late morning into the late afternoon from the East Slopes of the Cascades across the Columbia Basin onto the West Plains and Palouse. Friday`s high temperatures are trending cooler as the ensemble variability has decreased over the last 24 hours. Afternoon highs will be 10 to 15 degrees cooler than Thursday with readings mainly in the 60s. Rain shower chances have trended up too with a 50 to 60 percent chance of measurable precipitation for Kellogg, Sandpoint, Bonners Ferry and Metaline Falls. Vigorous west winds do not favor measurable rain in central Washington where there is a 10 percent or less chance for Wenatchee, Moses Lake, Ritzville, and Omak. Saturday and Sunday: The Polar Jet will continue to deliver active weather through the weekend. Temperatures will be seasonably cool with highs mainly in the 60s. West winds will continue to be breezy, but without big temperature swings our temperature and pressure gradients won`t be as strong as Thu/Fri. Sustained 10 to 15 mph winds with gust of 25 mph will be common with wind prone spots like the Cascade gaps and the Waterville Plateau reaching 30 mph or more. A broad trough and cool air aloft will generate afternoon and evening showers enhanced by the rising terrain of north Idaho and northeast Washington. The National Blend of Models (NBM) generates 20 to 40 percent chances of showers across the mountainous terrain around Sandpoint, Metaline, and Colville Saturday. Shower chances increase Sunday afternoon to 30 to 50 percent for north Idaho as well as the mountainous terrain of northeast and north central Washington. A few of the strongest cells will be capable of lightning and pea hail. Monday through Wednesday: Ensembles have trended cooler early next week. Compared to 24 hours ago, more of the ensembles are forecasting highs in the 60s early next week with fewer members in the 70s. Tuesday and Wednesday will be days to watch for the potential for widespread precipitation. The operational runs of the GFS, ECMWF, and Canadian models dig a low into Washington and north Idaho Tuesday or Wednesday. There are timing differences between the operational runs as well as their respective ensemble suites. While it is too early to count our chickens before they hatch, this trend is encouraging. Our region could use more spring rain. /GKoch && .AVIATION... 12Z TAFS: VFR conditions will continue through the upcoming period with bands mid to high level clouds streaming in from the northwest. Winds will pick up through the Cascade gaps again Wednesday afternoon and evening. FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence in VFR conditions. ----------------------- 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 77 52 77 45 64 41 / 0 0 10 10 20 0 Coeur d`Alene 76 50 75 44 60 40 / 0 0 10 10 40 10 Pullman 73 50 73 45 59 40 / 0 0 0 10 20 0 Lewiston 82 56 83 52 68 45 / 0 0 0 10 10 0 Colville 79 48 76 39 64 36 / 10 10 20 10 40 10 Sandpoint 74 50 72 43 58 39 / 10 10 30 30 60 20 Kellogg 71 53 70 45 55 42 / 10 0 10 30 50 10 Moses Lake 84 51 80 45 69 42 / 0 0 0 0 0 0 Wenatchee 81 55 75 47 65 45 / 0 0 0 10 0 0 Omak 84 53 78 43 69 42 / 0 0 0 10 10 0 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...None. && $$