199 FXUS65 KBOI 272024 AFDBOIArea Forecast Discussion National Weather Service Boise ID 224 PM MDT Sat Sep 27 2025
.SHORT TERM...Tonight through Monday night...Latest models continue warm, dry weather through Sunday, except for a 10-20 percent chance of thunderstorms Sunday afternoon and evening near the south-central ID/NV border due to a weak upper low in NV. The strong Pacific cold front and supporting deep upper trough in the Gulf of Alaska are now forecast to reach our CWA a few hours later than previous forecast, with eastern Oregon getting its first sprinkles before sunrise Monday, western Idaho getting its first rain Monday morning, and central Idaho Monday afternoon. The delay will also allow south-central Idaho to stay warmer and drier than before through the morning hours. Rainfall will maximize Monday night in Idaho while decreasing in eastern Oregon. Rain amounts look less than before, with Monday having generally less than 0.25 inch, and Monday night around .50 inch in the Idaho mountains and 0.25 inch in the Idaho valleys and eastern Oregon, with more to follow on Tuesday. Instability supports a chance of thunderstorms Monday afternoon and evening, more in Idaho than in Oregon. Winds will stay light through Sunday, except SW gusts will increase to 30 mph in southern Harney County Sunday afternoon. Winds will become west or northwest 10-20 mph behind the cold front Monday, with strongest gusts (near 40 mph) in southern Harney County Monday afternoon and evening.
.LONG TERM...Tuesday through Saturday...A strong upper low over the Western coast of British Columbia will continue to steer shortwave troughs across the Northwest region Tuesday through Saturday. Widespread precipitation and significant cooling are expected throughout the area from Tuesday to Friday. Peak valley temperatures are expected to trend down into the lower 70s Tuesday and into the upper 60s Wednesday to the end of the week. Tuesday afternoon will see favorable chances for thunderstorms, mainly for Southwest Idaho. The expected cooling trend and increasing cloud covers will mostly hinder convective potentials through the rest of the week except Thursday, as an embedded shortwave trough may develop thunderstorms over the central mountains. The highest elevations may see a rain-snow mix throughout the extended period. Long-term guidances generally favor the upper low steering into the area as a longwave trough Friday through Saturday. Saturday will mostly see precipitation concentrated along higher elevations.
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.AVIATION...VFR and clear skies. Surface winds: variable and E-SE 5-15 kt. Winds aloft at 10kft MSL: S-SW 10-20 kt.
KBOI...VFR with clear skies. Surface winds: SE 10-15 kt with brief gusts up to 20 kt through the afternoon, becoming variable under 7 kt after 00z.
Sunday Outlook...VFR. Slight chance of showers/thunderstorms in S-central Idaho Sunday afternoon and evening. Storms capable of localized outflows up to 30 kt. Increasing mid/high-level clouds Sunday. Surface winds: SE-SW 5-15 kt through Sunday. Winds aloft at 10kft MSL: S-SW 15-25 kt.
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.BOI WATCHES/WARNINGS/ADVISORIES... ID...None. OR...None.
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SHORT TERM...LC LONG TERM....JY AVIATION.....JY
NWS BOI Office Area Forecast Discussion