textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Unsettled conditions through the afternoon today, with showers mainly over the lower Magic Valley.

- Cold morning temperatures this morning and Wednesday morning will bring patchy frost and near-freezing conditions, with Frost Advisories in effect for the Snake Plain valley areas.

- Warm and dry conditions Wednesday through the weekend. Temperatures reaching up to 10 degrees above normal by Friday.

SHORT TERM /Through Thursday Night/

Issued 309 AM MDT TUE OCT 13 2026 The closed upper low has moved south of us into the Great Basin, and will shift eastward out of the region today (Tuesday). The low's remaining moisture load will continue some precipitation over the lower Magic Valley near the NV border this morning through the afternoon, before completely tapering off by the evening. Snow levels in the 4500-6000 ft MSL range over south-central ID will continue some light snow showers over high terrain areas of the southern highlands and the Owyhees. Low nighttime temperatures near freezing, coupled with some high surface moisture, will bring dense frost coverages over most areas this morning and Wednesday morning. As such, a frost advisory remains in place over the Snake Plain through Wednesday late morning. Otherwise, a Pacific ridge of high pressure will quickly build in by tonight, bringing daytime temperatures up to near and above normal with dry conditions areawide through Thursday. Wednesday will see temperatures hovering slightly above normal, mainly over the lower Treasure Valley areas. Thursday will see peak temperatures 5 to 10 degrees above normal as the Pacific high further amplifies over the northwest region.

LONG TERM /Friday through Tuesday/

Issued 309 AM MDT TUE OCT 13 2026 Friday through Saturday will continue to see dry conditions and temperatures 5 to 10 degrees above normal as the large Pacific high continues to build in and amplify over the region. Clear skies and good radiational cooling overnight will allow for mountain valley fog development through the mornings. On Sunday, a weak shortwave trough will pass over the northwest and bring a dry cold front across our area. This frontal passage may bring a slight cooldown Sunday through Monday. For now, temperatures are still looking to be 5 to 10 degrees above normal on those days. Ensemble guidance remains in strong agreement on another closed upper low digging into the region from the Gulf of Alaska late Monday through midweek. Although slight uncertainty remains over the intensity and coverage, most areas should see some moderate chances of precipitation late Monday through Tuesday.

AVIATION /12Z Tuesday through Wednesday/

Issued 411 AM MDT TUE OCT 13 2026 Generally VFR. Scattered rain showers and low clouds will bring intermittent MVFR ceilings to the Magic Valley this morning through the early afternoon. Patchy valley fog in central ID mountains bringing brief MVFR/IFR conditions. Mountains obscured in low clouds and precipitation with snow levels around 4500-5500 ft MSL. Widespread clearing in the evening. Surface winds: W-NW 5-15 kt with gusts 20-25 kt mainly over Snake Plain this afternoon through evening. Winds aloft at 10kft MSL: N-NE 10-20 kt becoming N 20-30 kt by Tues/12Z.

KBOI...VFR with clearing skies today through Wednesday. Surface winds: NW 8-15 kt with gusts up to 20 kt in the afternoon, becoming variable less than 6 kt in the evening.

BOI WATCHES/WARNINGS/ADVISORIES

ID...Frost Advisory until 10 AM MDT Wednesday for IDZ012-014-016. OR...Frost Advisory until 10 AM MDT /9 AM PDT/ Wednesday for ORZ064.