Area Forecast Discussion
Issued by NWS Boise, ID
Issued by NWS Boise, ID
730 FXUS65 KBOI 212134 AFDBOI Area Forecast Discussion National Weather Service Boise ID 234 PM MST Thu Nov 21 2024 .SHORT TERM...Tonight through Saturday night...A slow moving deep trough off the Pac NW coast will continue to funnel moisture into the region on a southwest flow. The focus of precipitation will stay across SE Oregon and portions of SW Idaho through tonight while remaining north of the western Magic Valley. This will continue to be a mostly orographic event with the bulk of precipitation falling across higher terrain while lower elevations see periods of light rain. As warmer air builds, snow levels will push above 7000 across the east-central Oregon and w-central Idaho mtns, and to above 8000 feet along the NV border. A ripple in the flow on Friday will bring warmer southerly winds into the region. Most areas will see a break in the precipitation with possibly some breaks in the clouds across lower elevations. Temperatures will warm to 10-15 degrees above normal. The western Magic Valley will be the warmest spot, seeing a 40% chance of reaching 60 or warmer. The trough moves onto the coast Friday night, bringing a return of rain and high mountain snow. A frontal passage early Saturday will bring a wind shift and initiate a drop in snow levels while also cutting off the main moisture tap. So while mtn valleys will likely see a changeover to snow, accumulations will be light as precipitation intensity decreases. Instability Saturday afternoon will support showers and possibly a thunderstorm mostly across the central and northern portions. Temperatures are 5-10 degrees cooler on Saturday, though still slightly above normal. Snow accumulation will be heaviest at 7kft MSL and above, where 1-2` of additional snow is expected through Saturday. This will translate to 1-2" of rain or liquid equivalent in the mountains while lower elevations could see up to 0.75". .LONG TERM...Sunday through Thursday...After a weak ridge briefly passes over the region Sunday, SW flow aloft will redevelop ahead of an upper level low off the coast. The low is forecast to open up and move east, moving over our CWA Tue or Tue night. Relatively dry NW flow will then dominate our weather Wed and Thanksgiving Day. Overall, this keeps a mention of precipitation in the forecast through most of the long term, with snow levels 3500-4500 ft AGL Sunday through Tuesday, falling to 2500-3500 Wed and Thanksgiving Day. Although it will be cold enough for snow on most valley floors Wed and Thu, very little if any precipitation is forecast in the valleys. Precipitation will even be light in the mountains, especially compared to what they are experiencing with the current atmospheric river event. Only 1 to 3 inches of new snow are forecast for the mountains in the long term period, with only a trace currently forecast for lower elevations. && .AVIATION...Mostly VFR. Widespread rain/snow creating MVFR/IFR at times, especially in the mountains. Mountain obscuration. Snow levels initially 5500-7500 ft MSL, rising to 7500-8500 ft AGL tonight. Surface winds: SW to SE 10-20 kt, gusts 25-35 kt, decreasing overnight but continuing still stronger than normal. Winds aloft at 10kft MSL: SW 35-50 kt, decreasing to 25 to 40 overnight. .KBOI...Mainly VFR, with frequent periods of rain. MVFR ceilings possible in heavier rain. Surface winds: S to E 7-17 kt with gusts up to 20-30 kt, continuing through the night. WEEKEND OUTLOOK...Periods of MVFR/IFR in precipitation Friday, with best chance from KBNO-KBOI-KSUN and north. Mountains obscured. Snow levels around 7000ft MSL. Surface winds SE-SW 10-20 kt, with gusts 25-40 kt. Cold front Fri night thru Sat, bringing widespread rain/snow and MVFR to LIFR conditions at times. Lowering snow levels to 4500-5500ft MSL Saturday. Surface winds becoming SW-NW 5-15 kt, gusts to 20-30 kt. Drier and VFR Sunday, except in patchy fog. && .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 SHORT TERM...DG LONG TERM....SP AVIATION.....SP