textproduct: Pocatello

KEY MESSAGES

- Scattered thunderstorms return to all of southern Idaho. Thunderstorms continue through the next seven days for many locations in southern Idaho.

- Red Flag Warnings in place for scattered thunderstorms today for all of Central Idaho Dispatch area, Southern Idaho Dispatch area, and portions of the Eastern Idaho Dispatch area.

- After record heat the past two days, clouds and precipitation will cool afternoon highs significantly today, then continue a weak overall cooling trend through Friday.

DISCUSSION

Issued at 211 AM MDT Sat Aug 22 2026

Long wave ridge will allow a weak shortwave to move through the mean southwest flow over the Gem State. This will enhance the thunderstorm activity in the already moist and unstable air over the forecast area. SPC has put nearly the entire forecast area in a marginal threat of severe thunderstorms (except a small wedge in Bear Lake County at the border with Utah. Thunderstorm threat is as high as 40 percent in the southern and eastern highlands. Could easily get G50KT for thunderstorm outflow.

The increased moisture will mean more clouds and rainfall can cause evaporative cooling to bring the record temperatures of Thu and Fri down some 3 to 8 deg F. The cooling continues into Sun and Mon, but at a slower rate, with temperatures still in the upper 80s to around 90 on Sun and Mon. Overnight lows continue mild with the cloud cover.

Wind stays weak today, but Sun will see 14 to 24 mph wind in the central Idaho mountains and the northwest side of the Snake River plain. Wind of this strength does not show up again until perhaps Thu.

For other items in the extended (Tue through Fri), the strong upper level ridge is finally beaten down in some of the clusters on either Thu or Fri, but still only affects the forecast area in about 53 percent of the solutions. Upper level flow appears more southwest than south, which should cut down significantly on thunderstorm coverage during the extended period.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/

Issued at 504 AM MDT Sat Aug 22 2026

Incoming moist and unstable air is already in with some SHRA still going on in the northeast corner of the forecast area, including KDIJ. By 22/19Z the showers have spread to all airdromes, and shortly after that starts, PROB30 groups for TSRA develop at all five airports. The farther north, the longer it takes for TSRA to reach there. SPC has put all the locations in a marginal risk of severe TSRA forecast, so expect G45KT and higher possible. Do not see much in the way of precipitable water, so do not anticipate a reduction in VSBY, and no impactful CIG due to the TSRA, or whatever light SHRA may develop. However, there should be some areas with CIG getting below 7000ft AGL.

Wind outside of thunderstorms should remain light, with none of the hourly model outputs indicating gusts exceeding 20KT. But watch for nearby TSRA.

There is one airport that has a forecast of 25 percent risk of TSRA every hour for three hours. That would be KPIH, from 22/22Z to 23/01Z. This is rarely seen in NBH output, so have gone TEMPO here with the TSRA condition. This should be monitored for timing, but it makes complete sense that the hours of maximum heating should cause the heaviest and highest thunderstorm coverage.

FIRE WEATHER

Issued at 211 AM MDT Sat Aug 22 2026

An influx of moist and unstable air, including the possibilities of outflow from a thunderstorm hitting 58+mph, will reach nearly everywhere in the Fire Weather Forecast area. Coverage of thunderstorms this afternoon and evening peaks at 25 percent to 45 percent, so Red Flag Warnings were issued yesterday for abundant lightning. Thunderstorm coverage lowers considerably for Sun, but then may be up again on Mon.

Fortunately, the moist air is pushing humidity readings up. Most readings will stay well above the 15 percent threshold for critical fire weather criterion. Cloud cover helps, as the high temperatures that lately have been setting records will be solidly cooler. The cooling and more humid trend continues through Mon. One offset to this is that the cloud cover will keep temperatures warmer at night, so recovery may not be as good, unless some wetting rains occur.

Wind will be up on Sun, mainly over the central Idaho mountains and the Snake River plain/eastern Magic Valley. It should be enough to meet critical fire weather speeds, but the humidity should be too high for any sort of critical fire weather situation. More wind develops Thu afternoon, but temperatures should be even cooler than this weekend, which bodes will for humidity readings.

PIH WATCHES/WARNINGS/ADVISORIES

Red Flag Warning from noon today to 9 PM MDT this evening for IDZ410-422-425-427-475-476.