textproduct: Boise

KEY MESSAGES

- Fire weather risk continues due to thunderstorm activity into Saturday.

- Thunderstorms with heavy rain may also increase the risk for flash flooding, especially for recent burn scars today and Saturday.

- Temperatures near to slightly below normal through early next week.

SHORT TERM /Through Sunday Night/

Thunderstorm coverage will increase this afternoon becoming scattered across much of southeast Oregon and southwest Idaho. In particular, Baker County along with Owyhee and southern Twin Falls Counties have the high probability, 40% to 70%, of thunderstorms. The primary threats with this activity are strong outflow wind gusts up to 45 mph and heavy rainfall. The 18z BOI sounding sampled 1.06 inches of precipitable water, placing atmospheric moisture in the 95th percentile for this time of year. Given this abundant moisture, flash flooding is possible over recent burn scars. A Flash Flood Watch remains in effect this evening for the Fox, Powder, Tartar, and Wapiti burn scars. Additionally, Red Flag Warnings continue across portions of the Vale, Baker and Boise, districts as several new fires were initiated last night despite localized wetting rains. Activity looks to diminish overnight though a few storms could persist along the Nevada border and in the central Idaho Mountains.

Moving into Saturday, another wave of thunderstorm activity is expected to develop across much of Southwest Idaho. Afternoon instability combined with another shortwave passage should support more robust convection. Heavy rain cores will again be possible even for the Snake River Plain, prolonging the threat for flash flooding and debris flows across vulnerable terrain and burn scars, including the Wapiti and Big Grass fires.

By Sunday, a brief window of cooler and drier air will overspread the region as we sit between weather systems. A slight chance of showers and thunderstorms will linger primarily across the central Idaho mountains, while the rest of the forecast area remains dry. Overall temperatures throughout the short term period will hover near normal.

LONG TERM /Monday through Friday/

Another upper-level shortwave trough will swing through the Pacific Northwest on Monday, continuing the trend of suppressing the Four Corners ridge. Flow aloft will be shifting from the southwest to out of the west/northwest, keeping shower and thunderstorm chances to the higher terrain of Eastern Oregon and Southwest Idaho. PWATs will stay above 50th percentile through this shortwave moving through, leading to localized QPF bullseyes with these thunderstorms, but will diminish Tuesday under drier west/northwesterly flow. Slightly below normal / near-normal temperatures will continue Monday and Tuesday as the trough makes its way east through the Northern Rockies. Starting late Tuesday, a trend of the upper-level ridge amplifying over the Great Basin will begin, including the SW ID/SE OR region. The extent to which it intensifies is uncertain, however, temperatures will begin to warm Wednesday onwards. While this is happening Wednesday, the upper-level longwave trough that has been sitting offshore slinging shortwaves through the area looks to finally move onshore to end the work week. Again, timing is uncertain, however increased precipitation chances and wind gusts from southerly flow aloft are expected.

AVIATION /18Z Friday through Saturday/

Issued 1214 PM MDT FRI AUG 14 2026

Scattered showers and thunderstorms will re-develop this afternoon with outflows to 35-45 kt. The highest chances for thunderstorms will be around KBKE/KMYL and the KTWF/KJER area. Localized MVFR/IFR and mtn obscuration with rain shafts. New fires starts may stand to increase smoke density again, however confidence on that is low. Surface winds: variable 5-15 kt, with erratic gusts near storms. Winds aloft at 10kft MSL: W-SW 5-15 kt.

KBOI...VFR. Patchy wildfire smoke remains in the area. A 15% chance of showers and thunderstorms through this afternoon. Surface winds: SE or variable 5-10 kt through early afternoon. Transitioning to NW-N in the late afternoon.

Weekend Outlook...Isolated to scattered showers and thunderstorms continuing Saturday. Storms Saturday capable of heavy rain, strong gusty outflows, and MVFR/IFR conditions. Showers and thunderstorms largely taper off Sunday, with limited coverage near KBKE and the central ID mountains. Surface winds: SW- SE 5-15 kt Saturday, then SW-NW 5-10 kt Sunday. Light and variable during overnights.

BOI WATCHES/WARNINGS/ADVISORIES

ID...Flash Flood Watch until 8 PM MDT this evening for IDZ011. Red Flag Warning until 8 PM MDT this evening for IDZ423-424- 426. Flash Flood Watch through Saturday evening for IDZ013. OR...Flash Flood Watch until 7 PM PDT this evening for ORZ062. Red Flag Warning until 8 PM MDT this evening for ORZ673. Red Flag Warning until 7 PM PDT Saturday for ORZ674-675.