textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Temperatures warming through the end of the week with lower elevations around 100 degrees Thursday and Friday.

- Increased chance of showers and thunderstorms over higher terrain this weekend and into next week.

SHORT TERM /Through Thursday Night/

Issued 418 AM MDT TUE AUG 18 2026 An amplifying Four Corners ridge will turn up the heat across the region through Thursday. Today a weak wave passing to the north and the lingering of mid-level moisture will feed afternoon cumulus development across higher terrain of SW Idaho. A few of the cu will see enough growth to drop light rain and maybe a rumble of thunder in the w-central ID mtns north and east of McCall and along the ID/NV border south of Twin Falls. The heat will continue to build Wednesday and Thursday with temperatures pushing to around 100 across lower elevations. Wednesday is dry across the board. Increasing mid-level moisture on Thursday will support a 5-10% chance of thunder south of Twin Falls. Would expect gusty winds and little rain from any cells that develop.

LONG TERM /Friday through Tuesday/

Issued 418 AM MDT TUE AUG 18 2026 The upper ridge will hold through Friday bringing another day of 100 degree heat to lower elevations. A trough lingering off the West Coast will push inland late Friday, moving through the Interior NW on Saturday. Cooling aloft and increased moisture will support a 20-30% chance of showers and thunderstorms across higher terrain of e-central Oregon and SW Idaho Friday, shifting to mostly SW Idaho for Saturday and Sunday. Given precipitable water content in the 70-75th percentile, wouldn't be surprised to see the coverage and probability of showers/storms increase some as we get closer to the weekend. Clouds and cooling aloft will help bring temperatures back to near normal over the weekend. Models show the upper ridge rebounding early next week as the trough exits to the east. This will likely bring a return of above normal temperatures. Southeast Oregon remains dry into early next week while the western edge of monsoon moisture keeps a 10-30% chance of showers/storms over SW Idaho.

AVIATION /12Z Tuesday through Wednesday/

Issued 642 AM MDT TUE AUG 18 2026 VFR with mid-high clouds across far SE Oregon and much of SW Idaho. Scattered afternoon cumulus in mtns with isolated showers/thunderstorms north and east of KMYL and higher terrain south of KTWF. Surface winds: W-NW 5-15 kt. Winds aloft at 10kft MSL: W-SW 5-15 kt.

KBOI...VFR with scattered high clouds through this morning. Light surface winds with variable direction becoming NW in the afternoon.

BOI WATCHES/WARNINGS/ADVISORIES

ID...None.

OR...None.