textproduct: Boise

KEY MESSAGES

- 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/

An upper level ridge over the Northeast Pacific continues to amplify, maintaining a dry, northerly flow aloft across southeast Oregon and southwest Idaho. At the surface, a cool high pressure system centered over the Great Basin will linger through Thursday.

Clear skies, dry air, and light to calm winds tonight will create ideal conditions for strong radiational cooling. Low temperatures Wednesday morning are expected to run roughly 2 to 3 degrees colder than Tuesday morning across most low elevation locations. Values in the Treasure Valley are expected to drop into the low to mid 30s, supporting widespread frost development. A Frost Advisory remains in effect. Further east, colder air pooling into the Western Magic Valley will drive temperatures down to around 28 to 32 degrees, where a Freeze Warning has been issued.

Conditions will remain quiet and dry on Wednesday and Thursday. High temperatures on Wednesday will top out in the mid 60s for lower valleys, which is roughly around seasonal averages. As the ridge axis nudges slightly closer on Thursday, heights aloft will recover slightly. Expect high temperatures to reach the upper 60s to low 70s for the lower valleys, accompanied by light diurnal winds and clear skies.

LONG TERM /Friday through Tuesday/

Warm and dry conditions will end the week with high pressure aloft over the Great Basin; this will keep temperatures at 5-10 degrees above normal. A shortwave and associated weak cold front on Sunday will help drop temperatures a few degrees, although still in that above normal range. By mid-week next week, there is good agreement on another trough digging down from the Gulf of Alaska into the western CONUS. this system will bring a more significant cool down and widespread precipitation chances. Below normal temperatures are favored again come Tuesday.

AVIATION /18Z Tuesday through Wednesday/

Issued 1201 PM MDT TUE OCT 13 2026

VFR. Low clouds continuing near KTWF/KJER early this afternoon, clearing out to be mostly sunny area-wide by late afternoon. Surface winds: W-NW 5-15 kt with gusts to 20-25 kt this afternoon, then variable 5-10 kt overnight. Winds aloft at 10kft MSL: N 10-25 kt.

KBOI...VFR under clear skies. Surface winds: NW 10-15 kt with gusts to around 22 kt this afternoon. Becoming variable under 8 kt overnight.

BOI WATCHES/WARNINGS/ADVISORIES

ID...Frost Advisory until 10 AM MDT Wednesday for IDZ012-014. Freeze Warning until 10 AM MDT Wednesday for IDZ016. OR...Frost Advisory until 10 AM MDT /9 AM PDT/ Wednesday for ORZ064.