textproduct: Pocatello

KEY MESSAGES

- Heat Advisory has been expanded to include more areas for today. Afternoon temperatures start a cooling trend Saturday.

- A overall slight chance risk of thunderstorms today, a chance risk for Saturday in many places. Risk decreases slightly for Sunday.

- Breezy and gusty afternoon Sunday.

DISCUSSION

Issued at 224 AM MDT Fri Aug 21 2026

Today through Sun night...The upper level ridge overhead reaches its peak strength today, then a Pacific coastal low slowly shift eastward and starts to break down this very strong ridge. This brings in lower 500mb heights in eastern Idaho, and a stronger shift to southerly flow that allows remnants of the southwest monsoon to move into eastern Idaho. This will trigger thunderstorms even today, but even greater risk on Sat. The continued shift of the pattern eastward will mean lowered risk for thunderstorms in the western portion of the forecast area.

Temperatures continue very hot today, but the declining 500mb heights, along with increased cloud cover on Sat and Sun, bring a cooling trend to the high temperatures. The Heat Advisory will not be needed after today.

The shift in the pattern will also bring gradually stronger wind as the upper level low attempts to move inland. Expect gusty wind to develop on Sun afternoon.

Mon through Thu Night...The formerly coastal upper level low will break down the upper level ridge as it moves into southern Canada and moves through eastern Idaho longitudes up there. This will bring up moisture from the southwest monsoon each day, with declining moisture reducing the threat starting Tue afternoon, but not ending it. Wind stays light until Thu afternoon, but even then only breezy conditions expected.

AVIATION /00Z TAFS THROUGH 00Z SATURDAY/

Issued at 922 PM MDT Thu Aug 20 2026

Winds will be light tonight into tomorrow morning. Expect shower development with isolated thunderstorms late Friday afternoon, continuing through the night.

FIRE WEATHER

Issued at 224 AM MDT Fri Aug 21 2026

Despite the very hot temperatures, the movement of moist air from the southwest monsoon into the Gem State means that there are only limited areas of low humidity that reaches critical levels starting Sat afternoon. This is also due to low pressure moving in from the west that brings cooler air. The trade-off is greater thunderstorm coverage on Sat afternoon and evening, likely needing Red Flag Warnings for areas with critical fuels. Expect breezy conditions in portions of the Snake River plain on Sun afternoon, but afternoon humidity will be in the 20 percent range. The thunderstorm pattern shifts to the east on Sun, leaving mostly slight chance-level of thunderstorm activity in all but the Eastern Idaho Dispatch area, where it will be close to critical thunderstorm criteria.

PIH WATCHES/WARNINGS/ADVISORIES

Heat Advisory from noon today to 10 PM MDT this evening for IDZ051>059-061-062-064-065-067-075.