textproduct: Pocatello

KEY MESSAGES

- Frost & freeze conditions fluctuate through the rest of the week

- Showers and thunderstorms tonight and Thursday

- Temperatures return to 10-15 degrees ABOVE AVERAGE over the weekend

DISCUSSION

Issued at 138 PM MDT Wed May 20 2026

Northwest flow remains in place across East Idaho under influence of low over Alberta/Saskatchewan Canada, with shortwave dropping through the Idaho panhandle and western Montana per satellite imagery. Short term high-res models continue to indicate areas of showers and isolated thunderstorms late this afternoon into the evening. Showers continue to sag south toward the southeast corner of the forecast area tonight into Thursday. Greatest precipitation still looks concentrated northeast of a line from Challis to Pocatello to Preston through the day Thursday. West of that line, model means generate very little to under a tenth of precipitation. Amounts increase east of that line, rising to 0.35-0.50" in highlands along the Wyoming border. Heavier showers could drop precipitation amounts exceeding 0.50", and the highest probabilities for this are 40-60% in the vicinity of the Big Hole range and Teton Valley. Temperatures remain cool overnight but generally above freezing so snow levels remain confined to areas above 6500 ft across the north, and above 7500 ft across the south. Snow accumulation will remain light, even at higher elevations. Shortwave slips southeast through the day Thursday, allowing northerly gradient and cool temperatures to resettle into East Idaho. Breezy northeast winds may necessitate a LAKE WIND ADVISORY for American Falls Reservoir. Another night of frost and/or freeze headlines are likely Thursday night, with a greater than 75% chance of temperatures dropping below 36F for all areas north of a line from Pocatello to Arco. Some of those areas have a greater than 50% chance of temperatures below freezing, but less than a 15% of reaching hard freeze at 28F.

Moving into the weekend, a ridge of high pressure redevelops behind departing shortwave and ahead of next Pacific system due to arrive next week. Temperatures begin to rise again through the weekend, mitigating chances for additional frost or freeze headlines. There is very weak chances of isolated showers into the weekend, but confidence is low for any one area over another to see even light precipitation. A few ensemble members begin to introduce better chances of showers by Sunday, but more widespread unsettled conditions are not expected until Tuesday, continuing into most of the remainder of the week.

AVIATION /18Z TAFS THROUGH 18Z THURSDAY/

Issued at 1152 AM MDT Wed May 20 2026

VFR conditions in place currently but clouds will be on the increase over the next few hours along with the development of showers and maybe a thunderstorm or two. KIDA and KDIJ will see the most likely impacts from precip during the period but some are also possible at KPIH and KBYI where chances are a bit lower. Precip looks to remain to the west of KSUN for the most part with chances there of any shower development are less than 20 percent. SW/W winds currently in the 10-15 kt range will become more light and variable overnight and eventually northerly into the day on Thursday.

PIH WATCHES/WARNINGS/ADVISORIES

None.