textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Widespread precipitation continuing through the morning. A 10-20% chance of thunderstorms in SW-Idaho early this morning.

- Windy today behind a cold front. Gusts to 30-40 mph this morning then 20-35 mph this afternoon.

- Cool and dry this weekend, frost possible Saturday and Sunday mornings.

- Unsettled pattern setting in again late Monday.

SHORT TERM /Through Sunday Night/

Issued 250 AM MDT FRI OCT 23 2026 Rain showers will continue overnight into Friday morning as the upper low moves northeast over our area. Model soundings hold on to elevated instability prior to a cold frontal passage. This elevated instability will give way to a 10-20% chance of thunderstorms across southwest Idaho early this morning. With earlier activity saturating the low levels, and the nocturnal stable layer in place, the wind threat has diminished greatly, with brief heavy rain the primary hazard with thunderstorms. The Flash Flood Watch will continue this morning for recent burn scars in the Boise Mountains. The threat of thunderstorms will diminish behind a cold front by the afternoon, with precipitation tapering off from W-E through the afternoon.

The aforementioned cold front is currently making it's way into eastern Oregon, pushing through SW Idaho through the morning. This front will bring W-NW winds with widespread gusts to 30-40 mph. Locally higher gusts to 45-55 mph will be seen in windier portions of Baker and Malhuer counties (including portions of I-84 where wind will be channeled through Baker Valley), through sunrise. Winds will taper off slightly as the front moves out this afternoon, but gusts to 20-35 mph will persist for much of the area. Snow levels behind the cold front will lower to 4.5-6 kft MSL in E-Oregon and 6-8 kft in SW-Idaho. The lowering snow- levels coincide with the precipitation tapering off, with just minor accumulations expected over higher peaks. Temperatures this afternoon will be quite a bit cooler than yesterday, with high temps generally in the 50s across lower elevations. Dry air and a shortwave ridge moving in behind this front will result in skies clearing from W-E across the area this afternoon into the overnight hours.

After the last of the precipitation moves out of the area Friday night, the aforementioned ridge will bring dry conditions for the rest of the weekend. Frost will be possible Saturday morning in lower elevations. However, breezy winds will persist which may hinder frost development outside of some localized areas. While Sunday morning will generally be slightly warmer, calmer winds will likely increase the frost risk in lower elevations. With clear skies and low level moisture supplemented by the rain showers, areas of fog may also develop in lower elevations.

LONG TERM /Monday through Friday/

Issued 250 AM MDT FRI OCT 23 2026 The short-wave ridge that kept the weekend dry will begin to break down Monday, as another low digs down the coast of British Columbia and into the northwest CONUS. Uncertainty remains on the exact timing of when this low will impact our area. Ensemble mean 500mb heights have it passing our area late Monday into Tuesday, which is reflected in the forecast with increasing precipitation chances Monday afternoon, peaking overnight Monday. The best chances of precipitation will come across higher terrain of SW-Idaho, with a 55-65% chance in Valley County, elsewhere north of the Snake Plain will carry a 30-50% chance. With this system bringing cooler temperatures and lowering snow levels, elevations above 6.5 kft MSL have a 35-60% chance of seeing at least an inch of snow between 6pm MDT Monday through 6pm MDT Tuesday; elevations above 7kft MSL have a 30-50% chance of seeing greater than 2 inches over the same period. Uncertainty increases beyond Tuesday with the pattern evolution. However, with the Grand Ensemble resolving zonal flow before general troughing, a cool and unsettled pattern is likely to continue. The CPC outlooks seem to agree, with our area highlighted with near normal temperatures and leaning towards above normal in regard to precipitation.

AVIATION /12Z Friday through Saturday/

Issued 525 AM MDT FRI OCT 23 2026

Widespread rain and mountain snow through the afternoon along/behind a cold front. Conditions will deteriorate with precip and front this AM, becoming low VFR to IFR in rain/low clouds and IFR-LIFR in mtn snow. Mountains obscured. Snow levels lowering from W to E to 5k-7kft by late AM. Precip tapering from W to E Fri aftn/eve. Surface winds: E-S 5-15 kt, transitioning to W-NW 15-25 kt with gusts 25-45 kt behind cold through Fri afternoon. Winds aloft at 10kft MSL: W-N 15-30 kt

KBOI...Increasing rain showers this morning with cold front, then tapering off from W to E Friday late afternoon. A 40% chance of MVFR/IFR due to lowering ceilings in rain before 18Z, then VFR. Surface winds: 10-20 kt with gusts 20-30 kt.

Weekend Outlook...Improving conditions to VFR Friday night through Sunday, except patchy morning fog/low stratus Sat and Sun mornings. Surface winds: variable 5-12 kt Sat/Sun.

BOI WATCHES/WARNINGS/ADVISORIES

ID...Flash Flood Watch until noon MDT today for IDZ013. OR...None.