926
FXUS65 KPIH 191111
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
511 AM MDT Wed Aug 19 2026

.KEY MESSAGES...

- Mid-to-Late Week Heat Surge: Temperatures will steadily rise,
  reaching the low-to-upper 90s across lower valleys Thursday
  and Friday. Heat advisories are in effect for Thursday 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 244 AM MDT Wed Aug 19 2026

Dry conditions are in store for mid-to-late week as the ridge
of high pressure rebounds today, allowing southeast Idaho to
warm back into above-normal territory late this week. The
warming trend will continue through Friday, with widespread 90s
across our lower elevations by Thursday when the high pressure
ridge axis shifts directly overhead. A heat advisory is in
effect for Thursday and Friday for most of our lower elevation
areas.

While the details are still in flux, model ensembles show a
deep PacNW low shifting the high pressure ridge eastward this
weekend and opening the door for the return of monsoon moisture.
The ECMWF ensemble indicates precipitation as early as Thursday
afternoon while the GFS ensemble maintains dry conditions
areawide until Friday afternoon.

Saturday will likely be the busiest weather day for Southeast
Idaho, with scattered thunderstorms for portions of the region,
but 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 /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 510 AM MDT Wed Aug 19 2026

Expect VFR conditions and overall light winds under high
pressure through the period.

&&

.FIRE WEATHER...
Issued at 1225 PM MDT Tue Aug 18 2026

A ridge of high pressure builds in over the area today and
means temperatures begin to warm again with highs in the 80s to
low 90s and min RHs generally at or below 20 percent. Winds
look to remain on the lighter side during the "dry" time of
Wednesday and Thursday, so we are expected to stay below Red
Flag warning criteria. Models are hinting at some isolated
thunderstorms returning to the higher elevations as early as
Thursday afternoon, but those look VERY isolated at this point
with some increasing, but still isolated activity returning on
Friday as monsoon moisture returns to the area. This activity
picks up as high pressure over the Four Corners region is pushed
just a bit eastward by an area of low pressure moving into the
Pacific Northwest.

A deep PacNW low system moves northeastward over the weekend
and Saturday looks to be the most active day for our area. So,
we will watch Saturday as the next best day for needing any Red
Flag warnings for scattered thunderstorm coverage. Activity
continues on Sunday, but appears to be a bit more isolated once
again. Next week there is some disagreement on how systems will
behave, but with high pressure remaining over New Mexico and
Texas and troughing off the West Coast, we keep the door open
for more moisture to keep working into the area each at least
through Monday and Tuesday.

&&

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

&&

$$

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