textproduct: Pocatello

KEY MESSAGES

- Showers and isolated thunderstorms should end by early evening

- Gusty northerly winds expected through this evening

- Much warmer and mostly dry weather for Memorial Day Weekend

DISCUSSION

Issued at 119 PM MDT Thu May 21 2026

Upper trough shifting southeast across the region today. Northerly flow in place behind the trough axis continues to produce gusty northerly winds through the Snake Plain, and a LAKE WIND ADVISORY remains in place for American Falls Reservoir through the evening. Mainly isolated showers and thunderstorm or two will continue primarily over higher terrain. Highlands east of I-15 could see a few stronger cells produce precipitation approaching 0.25" today, but most convection expected to remain light. Cold temperatures in place once again tonight. Probabilities support a slightly better than 50% chance of temperatures dropping below 32 degrees across the Snake Plain north of a line from Pocatello to Arco. Deterministic NBM temperatures are largely above 32 degrees for most of the populated areas. Thus will maintain the FROST ADVISORY, and update the wording to suggest that a few locations could see temperatures below freezing. The threat for a hard freeze (below 28 degrees for lows) is minimal.

Models slowly build the ridge into East Idaho through the weekend. Weak impulses may be enough to allow isolated showers and a thunderstorm or two to develop primarily over higher terrain each day into the Memorial Day weekend. Moisture remains quite limited to any precipitation that CAN develop is expected to be limited to a few hundredths, at best, and potentially induce some gusty winds. Otherwise, warming trend looks to remain in place into the weekend with daytime highs increasing into the 80s Saturday through Monday.

By Tuesday, models continue to progress the next Pacific low inland, but there is still a lot of uncertainty among the ensembles and clusters on how that actually occurs. So while there is confidence on conditions becoming increasingly unsettled by mid week next week, the details remain muddled. Clusters are fairly evening split by midweek between developing a closed split flow low over the Great Basin, and progressing an open trough across the Rockies towards the Plains. Temperatures do cool off beginning Tuesday and precipitation chances increase for the remainder of the week.

AVIATION /18Z TAFS THROUGH 18Z FRIDAY/

Issued at 1202 PM MDT Thu May 21 2026

Still seeing some lingering showers and a few thunderstorms across the eastern half of the area this afternoon as the region remains on the western edge of an upper trough moving through Wyoming. KDIJ remains the most likely terminal with impacts from TSRA and MVFR CIGs. KIDA could see a brief shower under VFR skies with maybe a brief shower making it down to KPIH but chances here are low. KBYI and KSUN look to remain dry. As the trough continues to push away, will get some brief clearing over the region during the late evening/early overnight with some SCT/BKN mid/high level clouds expected to return around sunrise tomorrow. N/NE winds 10-15 kts become more light and variable overnight and into the day on Thursday with KSUN expected to see more of their usual diurnal cycle returning tomorrow.

FIRE WEATHER

Issued at 1225 AM MDT Thu May 21 2026

Showers with a few thunderstorms will persist through most of the day, with the bulk of the moisture expected along the Wyoming border. The portion of Zone 411 in western Wyoming will likely see the highest amounts of moisture, 0.20-0.40" with light snow accumulations on the higher peaks and ridgelines. There have been a few thunderstorms overnight, and would expect that potential to last through the day, with an uptick expect toward scattered coverage potentially across higher terrain from Driggs south through Bear Lake (411 and 413). Gusty northerly winds will develop as a cold front sweeps south across central and eastern Idaho. Heading into Memorial Day Weekend, temperatures rapidly warm up to 10-15 degrees ABOVE AVERAGE. The question is will we remain dry or storm free. There are indications that limited mid level moisture occasionally slides across the state, which COULD help induce at least some virga or sprinkles, or an isolated storm. Right now, the potential for that is 15% or less for any given day, BUT we will need to monitor this closely each day to see if we need to push that potential up a bit more. By the middle of next week, another round of showers and storms and cooler temperatures are expected.

PIH WATCHES/WARNINGS/ADVISORIES

Frost Advisory from 3 AM to 9 AM MDT Friday for IDZ052>054.