textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

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

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

- Much cooler with gusty winds and a chance of showers and thunderstorms Tuesday and Wednesday.

SHORT TERM /Through Sunday Night/

Issued 319 AM MDT FRI MAY 22 2026 A ridge of high pressure aloft in the eastern Pacific will shift inland today but also flatten, as a faster moving trough also comes inland across western Canada. Still, the ridge will cause further warming in our CWA today and Saturday. On Sunday westerly winds aloft will back to southwesterly as a deep upper low in the Gulf of Alaska moves toward the BC coast. This will result in even more warming, and also a slight chance (10-15%) of thunderstorms along the NV border late Sunday and Sunday night.

LONG TERM /Monday through Friday/

Issued 319 AM MDT FRI MAY 22 2026 Monday (Memorial Day) will be the warmest day of all as upper winds increase from the southwest ahead of the approaching deep upper low, which by late Monday will be just off Vancouver Island. By late Monday night the low will be inland over central Oregon and close enough to push a strong cold front into our CWA, with gusty winds and an increasing chance of showers in eastern Oregon. Models have come into much better agreement since yesterday and Tuesday again looks much cooler than Monday as the front moves across western Idaho, with gusty winds and more showers and chance of thunderstorms. This cold front has similarities to the front that brought strong winds and blowing dust to our CWA last week, but unlike that case, pre-frontal temperatures will not be as warm, and the thermal gradient across the front not as strong. In addition, the supporting upper low will be coming in from the northwest rather than directly inland from the west, which also argues for a weaker and slower frontal passage. Even so, this cold front will be significant with at least 20 degrees cooling behind it. The cool, showery weather will continue into Wednesday, then drying and warming Thursday and Friday.

AVIATION /12Z Friday through Saturday/

Issued 553 AM MDT FRI MAY 22 2026 VFR with scattered high clouds. Surface winds: variable less than 10 kt through 18Z, then W-NW 5-15 kt until 23/00Z.

KBOI...VFR with scattered high clouds. Surface winds: variable less than 10 kt through 18Z, then NW 10-15 kt until 23/00Z.

Weekend Outlook...VFR with mostly clear skies. Winds SE or variable 5-10 kt in the nights/mornings and W-NW 5-15 kt in the afternoons. Isolated thunderstorms near the ID/NV border Sunday aafternoon.

BOI WATCHES/WARNINGS/ADVISORIES

ID...None.

OR...None.