267 FXUS65 KBOI 141608 AFDBOIArea Forecast Discussion National Weather Service Boise ID 1008 AM MDT Sun Sep 14 2025
.DISCUSSION...Showers and thunderstorms are ongoing over Eastern Oregon and the OR/ID border this morning, with spatial coverage expected to increase over the next few hours. Storm motion will continue to be NE around 30 kts, as is already seen with current thunderstorms. The well-defined negatively tilted trough will continue through the region, with an associated cold front already moving through Eastern Oregon. Recent CAMs (HRRR, FV3, NAMNST) have some more isolated to scattered thunderstorms impacting the upper Treasure Valley area this afternoon and early evening. Convective parameters still appear favorable for gusty outflow winds up to 50 mph, small hail, and heavy rainfall. Storm tracks and intensity will need to be heavily monitored near burn scars. No changes to the forecast at this time.
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.AVIATION...Scattered showers and thunderstorms moving W to E through this evening. Storms capable of MVFR/IFR conditions, mountain obscuration, gusty outflow winds up to 45 kt, small hail, and heavy rain. Highest storm chances along/N of I-84. Otherwise, VFR. Smoke layers aloft, improving later today. Surface winds SE-SW 5-15 kt in the morning, becoming W-NW 10-20 kt in the afternoon and evening. Winds aloft at 10kft MSL: SW 10-25 kt.
KBOI...Mainly VFR with smoke layers aloft. 50% chance of a thunderstorm impacting the terminal between 20-01 UTC. Brief gusty winds over 40 kt, blowing dust, heavy rain and small hail possible. Surface winds: SE 5-15 kt overnight, becoming NW 10-15 kt gusts to 20-25 kt after Sun/17Z with cold front. Higher thunderstorm gusts.
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.PREV DISCUSSION... SHORT TERM...Today through Tuesday night...Clouds have increased this morning ahead of a negatively tilted trough moving across the region from southwest to northeast. Showers and thunderstorms along the cold front will reach southeast Oregon just before sunrise around 6 AM MDT, then progress east- northeast through the dayarriving at the IdahoOregon border around 1 PM MDT, the Treasure Valley around 2 PM MDT, and McCall/Banner Summit near 3 PM MDT. Additional showers and thunderstorms are expected behind the front across Baker County and the west-central Idaho mountains as the low center tracks just north of the area. Recent CAM guidance has shifted the best thunderstorm potential farther north, generally along and north of a RomeBoiseBanner Summit line.
Convective parameters remain favorable for a few stronger storms, with bulk shear near 30 kts and MUCAPE values around 500 J/kg. Hazards include gusty outflow winds up to 50 mph, small hail, and heavy rainfall. Precipitable water values are near the 85th percentile, and hourly rainfall rates could reach 0.5 inches with the strongest storms, posing a localized flash flood risk near burn scars.
An upper-level ridge builds into the region Monday, though temperatures will remain about 10 degrees below normal. Temperatures moderate back to near normal Tuesday as the ridge axis shifts east.
LONG TERM...Wednesday through Sunday...The upper-level ridge will hold over the area through at least Thursday, keeping mostly sunny skies and near-normal temperatures in place. Highs will warm to around 5 degrees above normal by Thursday. By Friday, a more complex synoptic pattern develops with a trough axis setting up along the West Coast and possibly two closed lows on either side of our area. Model solutions vary on their exact placement, but the general outcome points to cooler conditions with more cloud cover and a slight chance of showers Friday into Saturday. Temperatures will trend back toward normal by late week and into the weekend.
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.BOI WATCHES/WARNINGS/ADVISORIES... ID...None. OR...None.
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DISCUSSION...CH AVIATION.....JR SHORT TERM...JDS LONG TERM....JDS
NWS BOI Office Area Forecast Discussion