textproduct: Pocatello

KEY MESSAGES

- Heat Advisories Active Today: Heat Advisories remain in effect through this evening across lower elevations, where peak afternoon temperatures will reach the mid-90s to lower 100s.

- Severe Microburst Risk Tonight (4565 mph Gusts): Monsoonal moisture surging into deeply dry lower atmospheric layers (inverted-V profiles) will support evening and overnight thunderstorms capable of producing localized severe dry microburst wind gusts of 45 to 65 mph, especially across the lower Snake Plain, Magic Valley, and South Hills.

- Widespread Saturday Storms & Fire Concerns: Convective coverage increases markedly on Saturday, introducing heightened fire weather concerns from lightning and erratic outflow winds before the main trough exits into Western Canada on Sunday.

- Seasonable Late-August Trend Next Week: A modest ridge rebuilds next week, maintaining isolated afternoon monsoonal storm chances and near-normal temperatures in the mid-to-upper 80s.

DISCUSSION

Issued at 134 PM MDT Fri Aug 21 2026

Unseasonably hot conditions continue across eastern Idaho this afternoon, with widespread lower-elevation Heat Advisories remaining active through this evening. Temperatures have climbed rapidly into the lower 90s and are on track to top out in the mid-90s, with localized readings exceeding 100F across the lower Snake Plain and Magic Valley prior to peak heating. Mostly sunny skies will give way to increasing cloudiness late this afternoon and evening as a plume of monsoonal moisture surges northward through the Great Basin ahead of an upper-level trough entering the Pacific Northwest.

High-resolution convective-allowing models (CAMs) continue to advertise elevated shower and thunderstorm development beginning this evening and lingering into the early overnight hours. Forecast soundings reveal deeply inverted-V thermal profiles across the lower boundary layer, creating an environment highly efficient at generating strong convective downdrafts. Stronger storms tonight will be capable of producing localized microburst wind gusts of 45 to 65 mph, with the highest threat centered across the lower Snake Plain, Magic Valley, and South Hills. Nocturnal showers and embedded storms will persist through the first half of the overnight period.

Following a brief early-morning lull, a more widespread wave of showers and thunderstorms will overspread eastern Idaho on Saturday. The combination of widespread lightning strikes and gusty, erratic outflow winds will introduce elevated fire weather concerns across dry fuel beds. As the primary upper- level trough pushes northeastward into Western Canada on Sunday, large-scale forcing will wane, restricting lingering shower and thunderstorm chances primarily to the higher terrain.

Subtropical high pressure over the Four Corners will slowly attempt to rebuild toward the Great Basin early next week. However, the ambient upper-level flow pattern will remain favorable for sending weak, periodic pushes of monsoonal moisture into the Intermountain West. This will maintain at least isolated afternoon and evening thunderstorm chances through mid-week. Because 500mb heights are forecast to remain modest, extreme heat is not expected to return next week. Daytime maximum temperatures will hold right around seasonal climatological norms for late August, topping out in the mid-to- upper 80s across lower elevations with only isolated spots briefly reaching 90F.

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/

Issued at 1224 PM MDT Fri Aug 21 2026

VFR conditions continue with light winds and just some mid/high level clouds in place across eastern Idaho. As we move into the evening and overnight, expect increasing cloud cover and precip chances to be on the rise with VCSH continuing at all terminals. Could be some thunderstorm chance but confidence in placement and timing is too low at this time to include mention. Could have overnight showers in place with more widespread shower/storm coverage expected as we move into Saturday afternoon and evening.

FIRE WEATHER

Issued at 134 PM MDT Fri Aug 21 2026

Monsoon moisture is beginning to work its way back into Eastern Idaho today and will continue through this weekend. Isolated storms will begin to pop up across the area this afternoon and activity becomes a bit more widespread overnight, though how much lightning will continue into tonight is a bit more uncertain. Strong wind gusts to 60 mph will be the main concern with storms today and again tomorrow with portions of the area under a Marginal Risk for severe storms both days. As thunderstorms begin to fire on Saturday afternoon, coverage will also increase, so a RED FLAG WARNING has been issued for Fire Weather Zones 410, 422, 425, 427, 475, and 476 due to the scattered coverage. These will be a mix of wet and dry storms with some of the drier storms more likely up in the Central Mountains and storms becoming wetter farther east. This is also part of the reason for leaving FWZ 411 and 413 out of the RFW. Coverage in those two zones will be isolated to nearly scattered at times. Heading into Sunday, it will be breezy with wind gusts of 25 to 35 mph and min RHs still in the 15 to 20 percent range in the Central Mountains, so near-critical fire weather conditions will exist there again, but min RHs elsewhere will range from 20 to 30 percent. We will still see some isolated to nearly scattered thunderstorms on Sunday, too. In fact, this monsoon moisture will continue each afternoon through at least the first half of next week.

PIH WATCHES/WARNINGS/ADVISORIES

Heat Advisory until 10 PM MDT this evening for IDZ051>059-061- 062-064-065-067-075. Red Flag Warning from noon to 9 PM MDT Saturday for IDZ410-422- 425-427-475-476.