textproduct: Pocatello

KEY MESSAGES

- Marginal risk of severe thunderstorms in the southeast highlands today. Isolated thunderstorms forecast this afernoon and evening, and again Friday.

- Rainfall amounts from showers and thunderstorms way up on Saturday, with some areas having scattered thunderstorms.

- Today is the last hot day for a while. Strong cooling from today to Friday. Humidity trends higher.

DISCUSSION

Issued at 144 AM MDT Thu Aug 27 2026

Today through Sat night...A trough will enter the Canadian west coast tonight, shifting airflow to more southwest and increasing its strength. This will still allow some isolated showers and thunderstorms for the afternoon and evening tonight. Wind will also be much stronger than the barely there wind of the previous 6 days--not that it is approaching Wind Advisory. The airflow is also bringing in slightly warmer air, and this will be the warmest day of the next seven. SPC analysis is that there is a marginal risk of severe thunderstorms in the southeast highlands for today and tonight.

The model run tonight is doing things a little different. In the past few days, this trough was staying in southern Canada. However, tonight the trough turns into a closed low and digs southward into the American Pacific Northwest, and is still there on Sat afternoon. Strong upper level wind continues, and quite a bit more moisture is flowing into southern Idaho. Precipitable water over all but the central Idaho mountains exceeds or hovers around 1 inch, which indicates heavy rains. On the more positive side, extensive cloud cover could reduce the coverage of thunderstorms, and right now it appears as though scattered thunderstorms will be limited both Fri and Sat to the east and southeast highlands, mostly.

Extensive cloud cover, the troughing getting closer than previous model runs, and evaporative cooling is now generating a tremendous cool-down from today to Fri. 8 to 12 deg F from one day to the next, then another 1 to 5 deg F cooling from Fri to Sat. Overnight lows will cool substantially from tonight to Fri night, and then small drop Fri to Sat night, just not of the same magnitude as the high temperatures.

The closer proximity of the low now means overall stronger surface wind is likely. Sat and Sat night look particularly moderate at least for the Snake River plain, while today and Fri will only be that way in the afternoon.

Sun through Wed...On Sun night the closed low will eventually move to the east of Idaho. In its wake is a dry westerly flow. Temperatures continue in the cooling trend until Sun afternoon. Then clearer skies and strong sunshine will bring back a warming trend; by Mon, temperatures are back to near normal for the time of year. Wind will still be moderate to strong each afternoon and evening during this period. However, the thunderstorm and precipitation risk drops, well, precipitously, from Mon onward. The upper level ridge axis stays farther east that it has been lately, and this puts the monsoonal remnants moving into eastern Utah and Wyoming rather than southern Idaho--for most of the time.

A key thing, though, is that this change in the forecast is new. Will guidance keep this new closed low scenario, or dump it during the days model runs today. Stay tuned.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/

Issued at 501 AM MDT Thu Aug 27 2026

High pressure is starting to give way to a low that will eventually move into Washington state from the Pacific. Wind will be the main difference compared to previous days: expect some G25KT outside of the TSRA expected. TSRA only expected only at KDIJ, KIDA, and KPIH. Threat at KSUN is extremely low, and KBYI very low. SHRA should develop with these TS. The moisture coming in today remains mainly at or above 9000ft AGL, and by afternoon there should start being CIGs, but nothing impactful. VSBY not expected to be affected at this time. G45KT to be expected from TSRA outflow.

FIRE WEATHER

Issued at 144 AM MDT Thu Aug 27 2026

The weather forecast is trending wetter and significantly cooler for a few days starting Fri and continuing into Mon afternoon. A trough has been expected to cross through southern Canada, moving a a moderate pace for the summertime and bringing a moderate cool-down over a couple of days, then a gradual warming trend. This is changed in the overnight model runs.

A closed low now develops instead of a trough. Closed lows move rather slow. And even as of Sat this low is still west of Idaho. This pattern will allow abundant moisture now to flow into southern Idaho, upping cloud cover, precipitation amounts, and humidity. It will decrease temperatures more substantially; instead of a 8 to 12 deg F drop to the high over two days, the same period will experience a 11 to 16 degree drop now. With this closed low farther south than previous thinking, wind will be stronger as well. The unknown is what will happen to thunderstorm activity. If the cloud cover lingers and is extensive enough, not enough daytime heating will occur to trigger thunderstorms, except where breaks in the clouds occur.

Thus, all of these changes are favorable to wildland fire- fighting efforts, as long as this change is not a blip in the continuity of automated guidance.

PIH WATCHES/WARNINGS/ADVISORIES

None.