079 FXUS65 KBOI 180819 AFDBOIArea Forecast Discussion National Weather Service Boise ID 219 AM MDT Thu Sep 18 2025
.SHORT TERM...Today through Saturday night...Sunny and warm again today under persistent upper level high pressure. Moisture in southern California, with remnants of former tropical storm Mario, will surge northward today with a weak upper low, and rapidly increase middle and high clouds in our CWA tonight. Low levels will stay dry and no rain is expected in our CWA through Friday night, but the clouds will limit nighttime cooling and daytime warming from previous forecasts. On Saturday the dissipating upper low will generate a 10-20 percent chance of showers and thunderstorms near the NV border, drying Saturday night. Smoke from wildfires will stay mainly aloft with little if any smoke near the surface.
.LONG TERM...Sunday through Thursday...Saturday night`s clouds will be swept east on Sunday by a stronger Gulf of Alaska upper trough coming inland across the nw states. This trough will push a surface cold front across our CWA, with a 20-30 percent chance of showers and thunderstorms in our northern CWA mountains, and gusty west/northwest winds over southern parts of our CWA. Then clearing and cooling Sunday night through Monday as the cold front and upper trough move rapidly east. Sunny and warmer Tuesday under a new upper ridge behind the departing trough. Another upper low is forecast in from southern California Wednesday but models differ widely on the track of that low. For now we`re forecasting a 10-20 percent chance of showers and thunderstorms in all areas Wednesday, with temperatures as warm as Tuesday.
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.AVIATION...VFR. Smoke layers aloft producing some reduction in visibility. Surface winds: E-S 5-15kt. Winds aloft at 10kft MSL: SW 5-10 kt.
KBOI...VFR with light winds. Smoke layers aloft.
Weekend Outlook...VFR. Broken to overcast middle and high clouds through the weekend. Slight chance of showers and thunderstorms near the NV border Saturday afternoon. North Pacific cold front will bring a chance of showers and thunderstorms to northern areas Sunday, and gusty west/northwest winds to southern areas. Clearing west to east late Sunday.
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.BOI WATCHES/WARNINGS/ADVISORIES... ID...None. OR...None.
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SHORT TERM...LC LONG TERM....LC AVIATION.....LC
NWS BOI Office Area Forecast Discussion