Area Forecast Discussion
Issued by NWS Boise, ID
Issued by NWS Boise, ID
410 FXUS65 KBOI 071547 AFDBOI Area Forecast Discussion National Weather Service Boise ID 947 AM MDT Tue May 7 2024 .DISCUSSION... Northwesterly flow prevails across the region today on the western edge of a stalled upper low over the Northern Plains. The 12Z BOI sounding reflects steep tropospheric lapse rates, which will be enough to support marginal destabilization this afternoon amidst daytime heating for isolated showers. Any thunderstorm threat is expected to remain well east of the area. Generally northwesterly winds will prevail today - strongest across the Magic Valley where a Wind Advisory is in effect. Expecting a relatively quiet period overnight before a northeasterly push of moisture associated with a weak backdoor front from the Northern Rockies occurs early tomorrow morning. This will bring a 20-40% chance of precipitation to the central Idaho mountains (light snow above 4500 feet) later tomorrow morning. Otherwise, impacts will be minimal elsewhere. && .AVIATION...Scattered rain and snow showers with associated MVFR conditions and mountain obscurations will continue over higher terrain of southwestern Idaho and southeastern Oregon today..diminishing after sunset. Snow levels will be around 5000 feet msl. Sfc winds: W-NW 10-20 kt, increasing to W-NW 15-25 kt with gusts near TWF/JER to 35-45 kt after 15z. Winds aloft: W-NW 35-40 kt. KBOI...VFR. Sfc winds: NW 10-15 kt with gusts to 25 kt. Scattered rain showers over the mountains north and east of KBOI will have about a 20 percent chance of coming within the vicinity of the terminal. && .PREV DISCUSSION... SHORT TERM...Today through Thursday night...A cold front has moved through the area as a deep upper level trough remains over the WY/MT/SD. The instability from the cold air aloft (500mb temps around -27C) will keep a threat of showers over the area today, mainly focused over the mountains through this afternoon and evening. Temperatures will be around 15 degrees below normal today with the cool airmass. Windy conditions expected, with the strongest winds in the Magic Valley and southern Twin Falls County this afternoon, where a wind advisory remains in effect. Upper level ridging over the Pacific NW and southwest Canada will cut off the cold air source from the Gulf of Alaska, and the trough will weaken and remain stationary over the WY/MT/SD area through the short term. Wrap around moisture will keep a threat of showers over the ID mountains on Wednesday, but the rest of the area will remain dry, with about 10 degrees of warming on Wednesday. Breezy west to northwest winds continue on Wednesday, but the upper level winds shift to the north/northeast, which keeps the winds below advisory levels. The upper level ridge expands over the Pacific NW on Thursday, with northeast flow aloft keeping temperatures from realizing the full potential of the ridge. Record breaking temperatures possible over portions of the Pacific NW and British Columbia, but the center of the ridge will be north and west of our area, where the warmer temperatures are. Temperatures warm another 10 degrees on Thursday with dry conditions. LONG TERM...Friday through Tuesday...An east-west oriented ridge will be in place to start Friday, and will dominate our weather at least into Sunday. This will continue both the dry conditions and the warming trend. Temps will be 5-10 degrees above normal Friday, rising to 10 degrees above normal Saturday, and 10-15 degrees above normal Sunday. There`s now a >90% chance of exceeding 80 degrees Sunday for most of the Treasure Valley. Slight cooling is expected Mon-Tue, but temps should remain above normal. The vast majority of ensemble members keep the area dry through Tuesday, but the deterministic GFS brings a weak shortwave trough to the region. If this low-probability solution ends up verifying, we will have a chance for showers. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...Wind Advisory until 9 PM MDT this evening IDZ016-030. 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...KA LONG TERM....SP