070
FXUS65 KPIH 200917
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
317 AM MDT Thu Aug 20 2026

.KEY MESSAGES...

- Late Week Heat Surge: Temperatures will steadily rise,
  reaching the low-to-upper 90s across lower valleys today and
  Friday. Heat advisories are in effect for today and Friday.

- Monsoon Moisture Returns: Models show a high pressure ridge
  shifting east with an approaching low system, which will bring
  moisture from our south back into the area. Wetter and cooler
  conditions will return for the weekend into next week.

- Increased Fire Danger Saturday: Models show scattered
  thunderstorm coverage, which will increase fire danger across
  the area.

&&

.DISCUSSION...
Issued at 229 AM MDT Thu Aug 20 2026

Dry conditions are in store through Friday as high pressure
builds over the region, allowing southeast Idaho to warm back
into above-normal territory through Friday. HEAT ADVISORIES are
in effect for many valley locations as widespread temperatures
in the advised areas will range 93 to 98 degrees, with some even
reaching triple digits as the ridge axis shifts directly
overhead.

Models continue to show an upper low setting up along the PacNW
coast and thus shifting the ridge eastward this weekend. This
will open up the door for the return of monsoon moisture. The
ECMWF ensemble indicates precipitation as early as Thursday
evening while the GFS ensemble has trended a bit earlier with
the introduction of accumulating precipitation late
Thursday/overnight into Friday morning. While isolated activity
is anticipated on Friday, Saturday still looks to be the busiest
weather day for Southeast Idaho with scattered thunderstorms
for portions of the region.

Storm activity will trend isolated again heading into the later
weekend, although the active pattern will continue into at
least the first part of the next week as low pressure remains
off the coast with an area of high pressure set up over the
Southwest.

&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 1029 PM MDT Wed Aug 19 2026

Will have clear skies tonight with some mid and high level
clouds but not expecting ceilings on Thursday. Only site that
may be close to some convective activity on Thursday is BYI but
left it out of TAF for now.

&&

.FIRE WEATHER...
Issued at 203 PM MDT Wed Aug 19 2026

High pressure ridging will be directly overhead of southeast
Idaho most of today and will continue to lead to dry conditions
and hot temperatures. Very isolated storms are possible this
afternoon, mainly in the Bear Lake region. Min HRs are ranging
from about 10 to 20 percent today and winds remain on the
lighter side, gusting to around 20 mph.

Over the next few days, the high pressure ridge over southeast
Idaho will be pushed just slightly eastward as an area of low
pressure off the coast of the PNW moves into the area. The high
pressure moving east will allow some monsoon moisture to works
its way back into Eastern Idaho as early as this afternoon.
Though, as mentioned above, the potential for isolated storms
this afternoon remains quite low, generally less than 15
percent. Convective activity begins to increase on Friday, but
still looks to be mostly isolated. This weekend is when storms
become more scattered. So, Saturday looks like the next best
day for any Red Flag Warning potential, and perhaps Sunday.
However, activity will become a bit more isolated for some
locations in the second half of the weekend. The area won`t
totally dry out as we head into next week. In fact, isolated
storm chances will likely continue through at least the first
half of next week.

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from noon today to 10 PM MDT this evening for
IDZ051-054>057-075.
Heat Advisory from noon to 10 PM MDT Friday for IDZ051>059-075.

&&

$$

DISCUSSION...TW/Cropp
AVIATION...GK
FIRE WEATHER...TW/AMM