Area Forecast Discussion
Issued by NWS Spokane, WA
Issued by NWS Spokane, WA
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741 FXUS66 KOTX 161759 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 1059 AM PDT Fri Aug 16 2024 .SYNOPSIS... Thunderstorms will return today across the northern mountains with concerns for flash flooding over burn scars. More showers and thunderstorms are possible Saturday evening and night for central WA. Temperatures will be warmer on Saturday with dry and breezy northeast winds across the Columbia Basin, West Plains, and southeast Washington. && .DISCUSSION... Today through Saturday Night: Trough is swinging through the region providing isolated to scattered showers across the US/Canadian border, eastern WA and north ID. There have been a few lightning strikes through the night, but they have been very isolated in nature. The trough will continue to move north through the day. Surface instability will increase through the afternoon and bring a chance of additional showers and thunderstorms through the evening. Precipitable water values increase to about 150% of normal this afternoon across the north. In addition, there is good deep instability and very light winds throughout the vertical profile, looking at several soundings. Any storms that develop will be slow moving. This raises concern for flash flooding and debris flows from heavy rain from slow or stationary storms, especially over current and recent burn scars. Will continue the flash flood watch for Chelan and Okanogan counties for this afternoon and evening. Showers and thunderstorms will move out of the region this evening with a quiet period through Saturday afternoon. Mostly sunny skies Saturday with a shortwave ridge pumping up into the region briefly will allow temperatures to warm into the mid 80s to mid 90s, which is 4 to 8 degrees above average. The low that is sitting off the coast will push a wave up into Oregon Saturday afternoon. We will be keeping a close eye on this. Models are suggesting clouds will increase in the late afternoon across central WA. Good forcing with this wave and elevated instability will move in during the evening and bring a threat of showers and thunderstorms to mainly central WA through the night. Have mention of showers further east into eastern WA and north ID through the overnight hours, but wasn`t confident enough at this time to add thunderstorms. Higher confidence is across central WA. The concern with the thunderstorms will be gusty outflow winds and lightning through the night. /Nisbet Sunday through Friday: Unsettled conditions remain as the upper level low meanders off the Washington coast. Chances for showers/thunderstorms will linger into Sunday across the Cascades and northern mountains (10-20%). By next Friday, ensembles have the trough axis in nearly the same place! What is particularly remarkable about this stretch of weather is the strength of the desert southwest ridge. It is one of the strongest ridges in the last 20 years for August for the southwestern United States. Despite the Inland Northwest being influenced by the trough offshore, the strong high pressure in the southwest will help us sustain above average temperatures for much of next week. Models do suggest a small break from the warmth Thursday as a negative tilt shortwave comes ashore, which also signals greater thunderstorm potential by Wednesday. /Butler && .AVIATION... 18Z TAFS: Rain showers will continue across portions of northern WA, extreme eastern WA and the ID Panhandle, with isolated embedded thunderstorms possible through this afternoon and evening. Thunderstorms are not expected to impact TAF sites, but could go over smaller fields like Winthrop, Omak, Republic and Colville. Clouds will clear south to north through the late afternoon and evening hours. FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence for VFR conditions for the TAF period. /KD ----------------------- 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 80 55 90 59 86 57 / 30 0 0 20 0 0 Coeur d`Alene 76 54 87 58 84 56 / 50 10 0 20 0 0 Pullman 78 52 90 53 84 53 / 20 0 0 20 0 0 Lewiston 86 62 98 65 92 63 / 10 0 0 10 0 0 Colville 78 44 87 48 85 47 / 50 20 0 40 0 0 Sandpoint 72 50 84 55 83 53 / 80 10 0 20 10 10 Kellogg 74 57 86 60 83 60 / 60 10 0 20 10 0 Moses Lake 84 54 94 59 86 55 / 10 0 0 50 0 0 Wenatchee 84 62 90 63 84 62 / 10 0 0 60 10 0 Omak 86 58 94 63 90 58 / 40 10 0 60 10 0 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...Flash Flood Watch from 11 AM PDT this morning through this evening for Central Chelan County-Okanogan Highlands- Okanogan Valley-Upper Columbia Basin-Wenatchee Area-Western Chelan County-Western Okanogan County. && $$