633 FXUS65 KBOI 200857 AFDBOIArea Forecast Discussion National Weather Service Boise ID 254 AM MDT Sat Sep 20 2025
.SHORT TERM...Today through Monday night...Mid-level moisture in northern NV and CA will shift northward into our CWA today for a 15 to 30 percent chance of thunderstorms south of the Snake Basin, i.e., or more than yesterday. A cold front from the Gulf of Alaska will come in Sunday and develop more showers and thunderstorms from moisture in place over our CWA. Greatest chance of pcpn (60 to 80 percent) will occur in the Boise Mountains and eastern half of Valley County, ID. Showers and storms will also develop in the southern Sawtooths, and those storms may have stronger outflow winds (up to 50 mph) than the northern storms. The front will also bring 10 to 15 degrees cooling and shift winds to west/northwest 15 to 20 mph with gusts to 30 mph. Clearing west to east Sunday night, then mostly sunny, breezy, and cool Monday. Clear and calming Monday night with lows Tuesday morning in the upper 20s through 30s in the mountains and generally 40s in the valleys.
.LONG TERM...Tuesday through Saturday...High pressure is expected to return to the region Tuesday through Thursday, with a gradual warming trend each day. Temperatures will hover around 5 degrees above normal. Uncertainty enters the forecast Friday into Saturday, with around 60% of ensemble guidance suggesting a breakdown of the ridge and Pacific trough impacting the area. Blended model guidance suggests a slow drop in temperatures during this timeframe, with continued dry conditions. Close to 40% of ensemble guidance suggest eastern Oregon and southwest Idaho will see shower activity Friday into Saturday, so anyone with outdoor plans should monitor the situation closely. The most aggressive guidance suggests a 20-30% chance of precipitation Friday Night into Saturday.
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.AVIATION...VFR and scattered clouds. Isolated showers and storms along and south of the NV border this afternoon with potential impacts to KTWF/KJER. Main impact would be brief rainfall and gusty winds to 30 kt with the strongest storms. Surface winds: variable up to 10 kt. Winds aloft at 10kft MSL: S-E 5-10 kt.
KBOI...VFR with increasing high clouds. Surface winds SE around 5 kt becoming NW 5-10 kt with some variability, becoming SSE after sunset.
Sunday Outlook...Generally VFR, with a cold frontal passage expected Sunday afternoon. Showers and thunderstorms are expected along the front, with the highest chances for precipitation north of the Snake Plain in the higher terrain of NE Oregon and central Idaho. MVFR will be possible in the strongest storms along with gusty frontal winds. Surface winds less than 10 kt on Saturday increasing to WNW 10-20 kt.
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.BOI WATCHES/WARNINGS/ADVISORIES... ID...None. OR...None.
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SHORT TERM...LC LONG TERM....MC AVIATION.....MC
NWS BOI Office Area Forecast Discussion