textproduct: Pocatello

KEY MESSAGES

- Showers and thunderstorms will return and continue through the next several days

- Critical to near-critical fire conditions for thunderstorms expected Tuesday for thunderstorms and wind/humidity Wednesday

- Cooler temperatures expected from Wednesday onward as low pressure settles in across the western U.S.

DISCUSSION

Issued at 104 PM MDT Mon Aug 31 2026

A weak "wave" will lift north across eastern Idaho through tomorrow morning, bringing an increase in showers and thunderstorms including a few storms overnight. The best chance of rain will be generally east of an Oakley to Island Park line. We may see a few light showers to the northwest of that, but chances are currently under 20%. We could see some brief heavier downpours farther east, especially outside of the Snake Plain. There is a 10-50% chance of gusts over 35 mph, with high end approaching 45 mph. By tomorrow afternoon, the next round of showers and storms will already be developing. The bulk of this round will initially forming across the central mountains south through the Magic Valley and South Hills/Albion Mountains. Expect some heavy downpours and also a 40-90% for gusts over 35 mph, pushing 50-55 mph. This shifts quickly to the northeast tomorrow night. As low pressure along the coast, another "wave" races north on Wednesday. This will keep off another round of showers and thunderstorms, with the main focus being across the central mountains. There is a 10-40% chance of gusts over 35 mph as current timing pushes any risk of strong/severe storms into Montana. A couple of higher resolution models have isolated storms east of I-15 and around Island Park, but we currently have that potential under 10% in the forecast. The bigger issue will likely be increasing winds across the entire forecast area. The strongest winds would be across portions of the central mountains, Arco Desert/INL and along the Montana border. We pushed the Blend of Models forecast toward the highest end of the range based on trends and the pattern, which puts us close to WIND ADVISORY thresholds. Temperatures will remain in the upper 70s to mid 80s for highs again Tuesday, but drop back into 70s, even mid/upper 60s for higher valleys with the front on Wednesday.

Beyond that, general low pressure settles in along the coast into early next week. Initially, showers and storms will basically develop across the central mountains. Heading into the weekend, showers and storms will become more widespread. The amount of monsoon moisture does increase, so the potential for heavier rainfall may return. Of note, although the main GFS models is an extreme outlier, it wants to be aggressive with grabbing the remnants of tropical development in the Pacific and pull it north across Idaho. All other models (ECMWF and it ensembles, the GEFS and AIGFS) do not show this at all. Either way, temperatures look to remain cooler with highs in the 60s and 70s.

AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/

Issued at 440 PM MDT Mon Aug 31 2026

Showers will overspread east Idaho tonight. Expect vfr conditions through the night with some gusts to around 20 kts. Showers should move off during the morning hours with thunderstorms developing mid to late afternoon.

FIRE WEATHER

Issued at 135 PM MDT Mon Aug 31 2026

A mass of moisture is moving in from the south, arriving in southern Idaho in the early evening and in eastern Idaho around midnight, and central Idaho around Tuesday morning. Thunderstorms should develop by at least Tuesday afternoon with scattered coverage in the central Idaho mountains and the northern end of the Snake River plain. Red Flag Warning was issued for the norther portions of the Sawtooth NF. The higher threat of wetting rains in the northern half of the Snake River plain have made the lightning activity of lower threat.

The incoming moisture will mean cloudiness that will keep temperatures relatively cool, and thus humidity readings should be way up, at least for a little. May have to watch Fire Weather Zone 427 on Wed as humidity dries out first there, at the same time as wind increase to breezy to windy conditions.

Warming and drying develop for the middle part of the week, with Sunday being the next day of significant shower and thunderstorms activity.

PIH WATCHES/WARNINGS/ADVISORIES

Red Flag Warning from 1 PM to 9 PM MDT Tuesday for IDZ422.