textproduct: Boise

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/

A ridge of high pressure will continue to build into the region through the work week, bringing a steady warming and drying trend. Clouds have decreased across most of the region today, with a scattered cumulus build ups over high terrain in Central Idaho and near the ID-NV border. A few virga showers will continue near the ID-NV border through the evening, otherwise mostly clear and warm conditions will continue. Temperatures will increase to about 8-12 degrees above normal by Thursday, with lower elevations reaching near or slightly above 100F. A push of monsoon moisture will primarily stay to our south on Thursday afternoon, although there is a low chance (10-20%) of showers and thunderstorms over the Magic Valley late Thursday. Rainfall accumulations will be minimal with any thunderstorms that form, so gusty outflow winds and lightning are the primary concerns.

LONG TERM /Friday through Tuesday/

Southerly flow aloft brought about by the offshore Pacific low pressure system and the Four Corners upper-level ridge will keep temperatures hot on Friday. Another day of 100 degree heat to lower elevations is expected. The upper-level trough will move inland late Friday into Saturday, 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. Temperatures will be cooler behind this disturbance, lowering to near-normal Saturday and Sunday. Long-range models hint at the Four Corners ridge rebuilding over the area early next week with temperatures warming again. The real question will be moisture early next week; some models show a strong surge with high precipitation chances and QPF totals, while others show a more limited scenario. The current forecast shows somewhere in the middle, with a 10-30% chance of showers/storms over SW Idaho.

AVIATION /18Z Tuesday through Wednesday/

Issued 1120 AM MDT TUE AUG 18 2026

VFR with mid-high clouds across far SE Oregon and southern Idaho. Scattered afternoon cumulus in mtns with isolated showers/thunderstorms north and east of KMYL and higher terrain south of KTWF. High density altitude in hot afternoon temperatures. Surface winds: W-NW 5-15 kt. Winds aloft at 10kft MSL: W-SW 5-15 kt, becoming W 5-20 kt by 00z/Wed.

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.