Area Forecast Discussion
Issued by NWS Boise, ID
Issued by NWS Boise, ID
105 FXUS65 KBOI 131603 AFDBOI Area Forecast Discussion National Weather Service Boise ID 1003 AM MDT Sat Sep 13 2025 .DISCUSSION... Areas of fog are persisting in some mountain Valley areas this morning, including the McCall area. Expecting this to burn off by late morning. Otherwise, upper ridging overhead will lead to a quieter day weather-wise, despite anomalously high moisture levels observed, with only isolated thunderstorm activity confined to the central Idaho mountains. Clouds increase from the west later tonight ahead of an approaching offshore upper- level trough. && .AVIATION...Patchy fog mostly dissipated. Isolated showers and thunderstorms redeveloping over the central ID mountains this afternoon. Generally VFR through the TAF period though. Surface winds: variable less than 10 kt, becoming W-NW 5-15 kt this afternoon. Winds aloft at 10kft MSL: W 5-15 kt. KBOI...VFR. Light SE winds this morning, becoming NW 5-10 kt this afternoon. Sunday Outlook...A trough and cold front will bring scattered showers and thunderstorms to the area in the afternoon and evening. Storms may bring MVFR/IFR conditions, mountain obscuration, gusty outflow winds up to 45 kt, small hail, and heavy rain. Surface winds SE-SW 5-15 kt in the morning, becoming W-NW 10-20 kt in the afternoon and evening behind the cold front. && .PREV DISCUSSION... SHORT TERM...Today through Monday night...An upper-level ridge will briefly build over the area Saturday, bringing mostly sunny skies and allowing temperatures to rebound to near normal. The only exception will be a slight chance of showers and thunderstorms over the central Idaho mountains this afternoon. A potent, negatively tilted trough will move across the region Sunday from southwest to northeast, bringing a 30 to 60 percent chance of thunderstorms. Convective parameters support the potential for stronger storms, with bulk shear near 30 kts and MUCAPE values of 300 to 800 J/kg. This environment will be sufficient to produce gusty outflow winds up to 50 mph, along with small hail Sunday afternoon and evening as storms develop with the cold front. Heavy rainfall will also be a concern, with precipitable water values in the 80th to 85th percentile. Recent CAM guidance indicates that stronger storms could quickly produce 0.50 to 1.50 inches of rain, raising flash flood concerns near burn scars. The trough exits late Sunday night, with patchy fog possible in mountain valleys and areas that receive excessive rainfall. An upper-level ridge will rebuild on Monday, though temperatures will remain about 10 degrees below normal. LONG TERM...Tuesday through Saturday...A ridge will build over the area Tuesday, bringing mostly sunny skies and a return to near-normal temperatures. By Wednesday, highs are expected to rise to around 5 degrees above normal. Forecast confidence decreases beyond midweek, as ensemble guidance is split on the evolution of the next upper-level trough. The prevailing trend favors a shift toward more active northwesterly flow, which would support a transition to cooler temperatures late in the period. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...None. OR...None. && $$ www.weather.gov/Boise Interact with us via social media: www.facebook.com/NWSBoise www.x.com/NWSBoise DISCUSSION...JR AVIATION.....JM SHORT TERM...JDS LONG TERM....JDS