Area Forecast Discussion
Issued by NWS Boise, ID
Issued by NWS Boise, ID
192 FXUS65 KBOI 180222 AFDBOI Area Forecast Discussion National Weather Service Boise ID 822 PM MDT Mon Jun 17 2024 .DISCUSSION...Cold upper low passed directly over northern CWA zones today with rain and snow showers and local small hail, and was entering southwestern Montana this evening. Radar showed only scattered light showers this evening whereas yesterday`s models predicted a more organized band of pcpn wrapping around the departing low. Therefore low PoPs for tonight look good. Winds have also decreased below advisory levels. Tuesday will begin a strong warming and drying trend as heights steadily build, leading to hot weather this weekend. Saturday should be the hottest day before an upper trough comes into northern areas from the Gulf of Alaska. 850-700 mb thickness suggests 100-103 degrees in lower southwest Idaho valleys on Saturday but NBM MOS continues to forecast upper 90s. We don`t see enough moisture/clouds to limit the heat so 100+ degrees looks more correct. Either way, Saturday will be hot. No updates. && .AVIATION...Isolated showers will continue overnight, mainly in the mountains, while tapering off in the valleys around 06Z. Generally VFR, except MVFR/IFR conditions in rain and snow showers. Mountains obscured. Snow levels 4500-6000 ft MSL. Surface winds: W-NW 10-20 kt with gusts 20-30 kt, except gusts 30-40 kt near the Magic Valley terminals, becoming variable 12 kt or less by 06Z/Tue. Winds aloft at 10kft MSL: W-NW 20-35 kt. KBOI...Isolated showers with MVFR possible through 06Z, then VFR. Tuesday will be VFR. Surface winds: NW 5-15 kt with gusts 10-20 kt, becoming variable 6 kt or less around 05Z/Tue. && .PREV DISCUSSION... SHORT TERM...Tonight through Wednesday night...The core of the upper low was supporting scattered showers and isolated thunderstorms this afternoon, mainly over SW Idaho. The thunderstorms will be accompanied by gusty winds to 40 mph and small hail or graupel. Snow showers at higher elevations could result in localized light snow amounts, mainly above 6000 feet. The convection decreases in coverage and intensity later this evening as the low moves east. Windy conditions this afternoon (gusting to near 45 mph in s-central Idaho) gradually subside this evening. A Wind Advisory remains in effect for the Western Magic Valley until 7 PM MDT this evening. A weak upper trough on Tuesday could result in another round of showers in Baker County and central Idaho Tuesday afternoon. Instability is marginal once again, but enough to warrant a slight chance (less than 20 percent) of thunderstorms in central Idaho. The trough moves northeast Tuesday evening, ending the convection. A dry and stable southwest flow aloft develops on Wednesday. Temperatures trend 10-15 degrees warmer on Tuesday and an additional 5-10 degrees warmer on Wednesday. LONG TERM...Thursday through Monday...Dry conditions and a warming trend are favored by all the model guidance into the weekend due to a general southwest flow aloft. There is high confidence that valley highs will in the 90s by the weekend. Some of the ensemble members show slightly cooler temperature on Monday as an upper trough moves through the Pacific Northwest, although confidence is low. && .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...LC AVIATION.....SP SHORT TERM...BW LONG TERM....BW