textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Mostly dry with temperatures 10 to 15 degrees above normal through Memorial Day.

- Gusty winds Monday ahead of a Pacific cold front, resulting in elevated fire weather conditions.

- Much cooler with gusty winds and a chance of showers and thunderstorms Tuesday and Wednesday. Showers in Idaho Thursday, then drying and warming Friday.

SHORT TERM /Through Monday Night/

Issued 310 AM MDT SAT MAY 23 2026 No change to current warming forecast through Monday (Memorial Day). Most areas will also be gradually drier, but isolated thunderstorms will develop late today/evening near the OR/NV border, and along all of the northern NV border Sunday afternoon/evening and again Monday afternoon/evening. The hot, dry air, and isolated thunderstorms will increase fire danger in southern Malheur County where grasses have already become critically dry. A deep upper low from the Gulf of Alaska will push a strong cold front across southeast OR Monday evening and western ID overnight, bringing a wind shift from southeast to stronger northwesterly, rapid cooling, and a 20-40 percent chance of post-frontal showers and thunderstorms. The supporting upper low is forecast to track from just west of Vancouver Island Monday afternoon to western OR Monday night, slightly west of previous forecasts. Monday night should therefore be warmer than previously forecast especially on the Idaho side.

LONG TERM /Tuesday through Saturday/

Issued 310 AM MDT SAT MAY 23 2026 The strong cold front should be in western Idaho early Tuesday morning and the western Magic Valley before noon. But with the supporting upper low heading SSE into Nevada, the forward speed of the front will be slowed and winds not as strong as if the upper low were to push the front due eastward. Even so, the air behind the front will be 20 to 25 degrees cooler than ahead of it and will be strongly felt Tuesday. Showers and afternoon thunderstorms will be more numerous Tuesday and Wednesday but rainfall amounts will still be relatively light, ranging from less than .10 inch in the Snake Basin and most of eastern OR, to .10 to .25 inch in southern highlands and mountains, and .25 to .50 inch in Valley County, ID, heaviest in eastern Valley County. Showers will continue into Thursday on the Idaho side when the upper low is still in central NV. In fact, latest models have Thursday afternoon/evening even wetter than Tuesday. But Friday and Saturday look drier and warmer as the upper low should then be in Colorado.

AVIATION /12Z Saturday through Sunday/

Issued 602 AM MDT SAT MAY 23 2026 VFR. Mostly clear skies through 20Z. Isolated thunderstorms near the OR/NV border 23/21Z through 24/03Z. Surface winds: variable or SE less than 10 kt through 18Z, then W-NW 5-15 kt until 24/01Z, with gusts to 20 kt in SE OR and Magic Valley.

KBOI...VFR. Clear sky. Surface winds: SE 5-10kt until 18Z, then NW 7-12 kt until 24/00Z.

Sunday Outlook...VFR. Mostly clear skies through 24/20Z. Isolated thunderstorms near the NV border 24/20Z-25/06Z. Surface winds: SE or variable 5-10 kt until 24/20Z, then W-NW 5-15 kt until 25/00Z.

BOI WATCHES/WARNINGS/ADVISORIES

ID...None.

OR...None.