textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Continued very warm and dry through Friday.

- Much cooler, with showers, Saturday through Wednesday.

- Significant rainfall possible in Idaho next week, but confidence remains low.

SHORT TERM /Through Saturday Night/

Issued 359 AM MDT THU OCT 8 2026 An upper level ridge will continue warm and dry conditions today and Friday. Highs will be 10 to 20 degrees above normal, but generally a few degrees shy of record highs. Winds will be light today, but increase on Friday ahead of an upper level trough moving in from the northwest. Wind gusts of 25 to 35 mph will develop in the afternoon in the higher elevations as well as across southeast Oregon and far southwest Idaho. Gusty winds and low humidity will create elevated to critical fire weather conditions, especially across far southwest Idaho. Gusts of 15 to 25 mph are expected in the more sheltered lower elevations. A 5 to 10 percent chance of showers and thunderstorms will develop late Friday afternoon as the trough approaches.

A cold front associated with the trough will move across the area Friday night. This will usher in temperatures 20 to 25 degrees cooler on Saturday. Winds at lower elevations will increase along and behind the front, remaining breezy through Saturday. The upper level trough will develop into a closed low and move south across Washington on Saturday. Precipitation chances will increase across northeast Oregon and the west- central Idaho mountains Friday night into Saturday morning, with snow levels falling to 6000 to 8000 feet. A 30 to 70 percent chance of precipitation will then develop across central and south-central Idaho Saturday afternoon and night where southerly flow aloft will transport deeper moisture north. Rain and snow amounts through Saturday should be light.

LONG TERM /Sunday through Thursday/

Issued 359 AM MDT THU OCT 8 2026 The upper low will progress south across Oregon and into northern California on Sunday. The low will transport hurricane remnants originating from the eastern Pacific to the north. The bulk of this moisture is expected to remain south and east of our area, but is likely to clip south-central Idaho, including the Magic Valley, with significant rainfall possible Sunday and Monday. Confidence in significant precipitation amounts is lower to the west and north, but may also develop over the southwest Idaho highlands and central Idaho mountains. Snow levels will remain above 7000 to 8000 feet due to the tropical origin of the moisture. Instability will be very limited, but any embedded thunderstorms could produce heavy rainfall. In addition to the moisture, the low will also usher in cooler air, with highs dropping a few more degrees, except 10 to 15 degrees cooler across south-central Idaho where rain will hold temperatures down further. Highs will be around 10 degrees below normal, and lows in the agricultural valleys will dip into the 30s with frost possible especially if skies clear. Winds will remain breezy on Sunday, then taper off Monday.

The low will gradually move east on Tuesday, but how far south it travels before moving east will determine how much moisture wraps around into our area. For now, this results in a 20 to 40% chance of precipitation, highest across southern and central Idaho. Temperatures will rebound slightly, but remain below normal. Ensembles have come into better agreement that a Pacific trough will move across our area on Wednesday and exit the area Thursday. Rain and snow in this pattern will favor the west- central Idaho and Boise mountains, with light snow accumulations possible above 6000 to 7000 feet. This trough will also bring breezy conditions back to the area with continued cool temperatures. Precipitation should taper off by Thursday as an upper level ridge builds along the coast.

AVIATION /12Z Thursday through Friday/

Issued 603 AM MDT THU OCT 8 2026 VFR and clear, except areas of smoke/haze reducing visibility near prescribed burns, most likely to occur near KMYL. Surface winds: variable less than 12 kt. Winds aloft at 10kft MSL: W-NW 5-15 kt.

KBOI...VFR and clear. Surface winds: SE 4-8 kt this morning, then NW 4-8 kt this afternoon. SE 5-10 kt by mid-evening.

Weekend Outlook...Increasing clouds late Fri with a 5-10% chance of showers/storms late afternoon and evening. A cold front moves through Fri night with rain and snow developing across the north. Precip increases Sat, mainly across central and S-central Idaho, but may expand further west on Sun. Snow levels 6-8kft MSL across SW Idaho, 4-6kft SE Oregon. Mountains obscured at times with MVFR/IFR conditions possible in precip. Surface winds: SW-NW 10-20 kt with gusts to 30 kt across higher terrain on Fri; NW 5-15 kt with gusts 20-30 kt Sat/Sun.

BOI WATCHES/WARNINGS/ADVISORIES

ID...Fire Weather Watch Friday afternoon for IDZ423-426. OR...None.