textproduct: Pocatello

KEY MESSAGES

- Terrain-Driven Convection Today & Monday: An amplifying ridge removes large-scale forcing, but entrenched monsoonal moisture will support isolated-to-scattered afternoon thunderstorms over the mountains and highlands, producing localized gusty winds and brief heavy downpours.

- Enhanced Storm Potential Tuesday: A shortwave trough tracking through Montana across the top of the ridge will increase shower and thunderstorm coverage, primarily over northern and eastern high country.

- Late-Week Drying & Heat Surge: Northwesterly flow behind the departing shortwave will dry out the atmosphere for the second half of the week, with an amplifying ridge pushing lower- valley temperatures back into the 90s.

DISCUSSION

Issued at 245 PM MDT Sun Aug 16 2026

An upper-level ridge of high pressure will build across eastern Idaho today. While this building ridge will eliminate large- scale upper-level support for organized convection, deep monsoonal moisture remains firmly entrenched across the region. Driven by diurnal surface heating, isolated to scattered afternoon thunderstorms will develop primarily over the higher terrain and mountain zones. High-resolution convective-allowing models (CAMs) strongly support this terrain-driven convective placement. The primary hazards with any developing cells will be localized gusty outflow winds and brief, heavy downpours. Convective activity will taper off quickly this evening with the loss of solar heating, followed by a near-repeat setup on Monday afternoon.

A shortwave trough is forecast to traverse the northern perimeter of the ridge, moving across Montana from Monday night through Tuesday. Associated height falls and glancing upper- level energy will enhance shower and thunderstorm coverage across eastern Idaho during this timeframe, particularly over the Central Mountains, Continental Divide, and Eastern Highlands.

Behind the departing shortwave, upper-level flow will shift to the northwest as the ridge amplifies just to our west. This northwesterly trajectory will shunt the primary monsoonal moisture plume southward, pushing a drier air mass into the Intermountain West and significantly reducing daily thunderstorm chances for the second half of the week.

Daytime temperatures will steadily trend upward throughout the 7-day period. Expect afternoon highs to remain slightly below seasonal normals through Tuesday before surging above average Thursday through next weekend as the ridge axis locks over the region. Lower-elevation valley locations, including the Snake Plain and Magic Valley, will see a return to the 90s by late week.

AVIATION /00Z TAFS THROUGH 00Z TUESDAY/

Issued at 942 PM MDT Sun Aug 16 2026

TSRA have finally ended in the past hour. The continued drying out of the atmosphere will mean lower chances of TSRA activity in the afternoon on Mon. At this time, it appears as though KSUN will no longer be under a TS threat. KIDA appears to have little threat of SHRA, so if any TS develop, expect dry TS. Deep convection means outflow could be strong.

Outside of the TSRA risk, see no impact on airdrome operations due to CIG, should be at 9,000ft AGL or higher, if any. There is so little moisture, do not expect impact to VSBY even from TSRA.

Wind outside of TS should continue to be light, at 10KT or below, with overnight conditions variable.

FIRE WEATHER

Issued at 203 PM MDT Sun Aug 16 2026

A ridge of high pressure will continue building over the region today, although monsoon moisture will be abundant enough to support isolated to scattered convection the next couple afternoons. High resolution models feature isolated convection this afternoon across all Fire Weather Zones with isolated to scattered thunderstorms across the mountainous zones, most notably Fire Weather Zone 476. Thunderstorms will be capable of heavy rain and wind gusts up to around 45 mph.

A shortwave feature passing to our north will flatten the ridge on Monday before the ridge rebounds mid- to late week. This will mean slightly cooler temperatures on Tuesday before we warm back to around normal or slightly above normal later week. By next weekend, ensembles show a deep PacNW low shifting the ridge eastward and opening the door for the return of monsoon moisture.

PIH WATCHES/WARNINGS/ADVISORIES

None.