Area Forecast Discussion
Issued by NWS Boise, ID
Issued by NWS Boise, ID
059 FXUS65 KBOI 161609 AFDBOI Area Forecast Discussion National Weather Service Boise ID 1009 AM MDT Mon Sep 16 2024 .DISCUSSION...A trough of low pressure will influence the region today through Tuesday with below normal temperatures and the threat of precipitation. There will be a brief period this evening where storms could generate wind gusts of 30-50 mph across both SE Oregon and southwest Idaho. Current projections indicate a 20-40% of wind gusts of 30 mph or greater. The current forecast looks like it handles the scenario well and no updates are planned this morning. && .AVIATION...Generally VFR, with MVFR possible in/around showers later this afternoon and evening. Gusts to 40kt with the strongest storms, with the best chance near KJER/KTWF after 22Z. Surface winds: N to NW 5-15 with gusts to 25 kt in SE Oregon, and generally variable 5-10 kt in SW Idaho. Winds at 10kft: NE- SE 10-20 kt. KBOI...VFR. A 30-50 percent chance of showers, after 21Z. A 30 percent chance of thunderstorms after 21Z, with wind gusts up to 35 kt possible. Surface winds: variable mainly NW to 10 kt. && .PREV DISCUSSION... SHORT TERM...Today through Wednesday night... KEY POINTS *Isolated to scattered thunderstorms this afternoon will bring the risk for wind gusts in excess of 40-50 mph with locally heavy rain. *Temperatures will cool through Wednesday, with daytime highs about 10-20 degrees below normal. *Unsettled conditions with rain and cool temperatures will continue through the middle of the week with a slight warming and drying trend beginning early next week. The upper level low will continue to dive down over central California this morning, with a few showers and thunderstorms over the region as of 2 am MDT. Most of the thunder has been centralized over the Magic Valley and eastern Idaho. Showers will continue through the day, with an uptick in stronger thunderstorms across the region around 2 pm MDT this afternoon. Current high resolution guidance shows the storms moving from south to north near the Nevada border and east to west over the Central ID Mountains with outflow winds in the 40-50 mph range. Current QPF totals range from 0.4-0.7 inches of rain across much of the forecast area valleys for today through Tuesday night. Ridgetops could see anywhere from 0.8-1.0 inches of rain. Current hi- res probability guidance indicates a low chance (<10%) of reaching flash flood precipitation amount thresholds (0.50" in one hour), with the best chance over steep ridges in the Central ID Mountains and higher elevations in southeast Oregon. This low risk of reaching higher QPF lands us again in a marginal risk in the excessive rainfall outlook from the Weather Prediction Center. Weak showers and thunderstorms will continue through the overnight hours on Tuesday, tapering off as the low continues to move to the northeast early Wednesday. An extremely brief ridge will build in on Wednesday, ahead of another trough moving in late Wednesday in this double barrel low evolution. This low will eventually dry up quite a bit later this week, with below normal temperatures continuing through the short term period. LONG TERM...Thursday through Monday...Models generally agree on the initial position of an upper low in Nevada on Thursday, but differ with the timing of its eastward progression. Some of the ensembles favor a slower solution, while the bulk of the members are faster and show it moving into Utah on Friday. Forecast for our area will indicate a 15-30 percent chance of showers in SW Idaho and along the OR/NV border on Thursday, along with a slight chance (less than 20 percent) of thunderstorms near the ID/NV border. Mostly dry conditions follow on Friday, except for a slight chance (less than 20 percent) of showers near the ID/NV border south of Twin Falls. The weather for next weekend is uncertain, although the guidance has trended drier in the latest run. Previously, the models were depicting an upper low moving southeast into the northern Rockies and eastern Idaho, but the newer ones have favored a flatter and drier northwest flow aloft. Forecast remains generally unchanged until the models show consistency, so there is a 15-30 percent chance of showers Saturday through Saturday night, trending drier Sunday and Monday. Temperatures will depict little day-to-day trends, averaging 5 degrees below normal. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...None. OR...None. && $$ www.weather.gov/Boise Interact with us via social media: www.facebook.com/NWSBoise www.twitter.com/NWSBoise DISCUSSION...MC AVIATION.....MC SHORT TERM...SA LONG TERM....BW