textproduct: Boise

KEY MESSAGES

- Unsettled conditions through early Tuesday, mainly on the Idaho side, with showers mainly over Magic Valley and Boise Mountains.

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

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

SHORT TERM /Through Wednesday Night/

The closed upper level low center is positioned directly over the region this afternoon. This system will continue to trigger scattered showers and isolated mountain snow showers, primarily across southwest Idaho through late this evening. Shower activity will gradually taper off from west to east overnight as the low weakens and kicks eastward toward the Rockies. Precipitation amounts will remain light, with valley locations picking up a few hundredths of an inch and higher elevations seeing less than an inch of light snow above 7000 feet.

As shower activity diminishes overnight, clearing skies and light winds will allow for significant radiational cooling. Low temperatures tonight will fall into the lower to mid 30s across the lower valleys, with widespread 20s in the higher mountain valleys. Patchy frost is expected to develop late tonight into early Tuesday morning across the Treasure Valley and Western Magic Valley. Thus, a Frost Advisory has been issued for the Snake River Plain. Note that parts of the Magic Valley may avoid widespread frost tonight, as lingering clouds and showers through late morning could hold temperatures in the upper 30s.

A weak ridge of high pressure builds overhead Tuesday and Wednesday, bringing dry conditions and a slight moderating trend in daytime highs. However, another cold morning is on tap for Wednesday morning under clear, calm conditions. Minimum temperatures Wednesday morning will mirror Tuesday morning, keeping the threat for localized frost and near-freezing valley temperatures intact before temperatures recover slightly Wednesday afternoon. A Frost Advisory has been issued for Wednesday morning, though a Freeze Warning may be needed from Mountain Home through the Magic Valley where temperatures could drop into the 30 to 33 degree range. Frost and Freezes are typical for this time of year, usually occurring in the first few weeks of October.

LONG TERM /Thursday through Monday/

Warm, dry, and pleasant conditions will end the coming week as a Pacific ridge shifts to be over the Great Basin. This ridge will allow temperatures of 5-10 degrees above normal. Clear skies and good radiational cooling overnight will allow for a threat of mountain valley fog overnight into the mornings. A weak shortwave late Sunday will help lower temps a few degrees come Monday (although still leaning above normal). Flow aloft will become more zonal as a result, before becoming southwesterly Monday ahead of the next system. In the 7-10 day time frame, ensemble guidance is in good agreement on another trough digging down from the Gulf of Alaska. This will likely bring increasing chances of precipitation and cooler conditions by mid- week next week.

AVIATION /18Z Monday through Tuesday/

Issued 1148 AM MDT MON OCT 12 2026

Generally VFR. Lingering localized MVFR/IFR conditions in mtn valley low stratus early this afternoon. Areas of mtn valley fog/low stratus redeveloping overnight tonight. Showers continuing in S-Central ID, tapering off Tue/PM. Surface winds: W-N 5-15 kt. Winds aloft at 10kft MSL: Variable 5-15 kt becoming N-NE 5-15 kt.

KBOI...VFR. Skies clearing this evening/overnight, with mostly clear skies Tue/AM. Surface winds: NW 5-12 kt through the period.

BOI WATCHES/WARNINGS/ADVISORIES

ID...Frost Advisory from midnight tonight to 10 AM MDT Wednesday for IDZ012-014-016. OR...Frost Advisory from midnight MDT /11 PM PDT/ tonight to 10 AM MDT /9 AM PDT/ Wednesday for ORZ064.