881
FXUS65 KPIH 292316
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
516 PM MDT Tue Sep 29 2026

.KEY MESSAGES...

- Prolonged Quiet Weather Period: High pressure and dry air
  will keep eastern Idaho completely dry with minimal cloud
  cover through the workweek, upcoming weekend, and into early
  October. Zonal flow aloft will hold daytime highs near late-
  September averages in the upper 60s to lower 70s across lower
  elevations through Wednesday.

- Unseasonable Late-Week Warmth: An amplifying Great Basin
  ridge will boost lower-elevation temperatures into the upper
  70s and lower 80s starting Thursday and continuing through the
  weekend.

- No Fall-Like Weather in Sight: High confidence exists for
  above-normal temperatures and suppressed precipitation
  extending through the first full week of October.

&&

.DISCUSSION...
Issued at 100 PM MDT Tue Sep 29 2026

Afternoon satellite imagery displays mostly clear skies with
only a few stray cirrus clouds drifting across the region. A
broad, tranquil weather pattern is firmly established, marking
the beginning of a prolonged period of quiet weather across
eastern Idaho. Predominantly zonal upper-level flow over the
next couple of days will maintain light surface winds and hold
daytime maximum temperatures right around seasonal
climatological norms. Lower-elevation valleys will top out in
the upper 60s to lower 70s through Wednesday, accompanied by
clear, crisp overnight lows in the upper 30s to upper 40s.

A transition toward unseasonable warmth develops during the
second half of the workweek. Operational models and ensemble
guidance agree that an upper-level ridge anchored over the
southern Great Basin will amplify northward across the
Intermountain West on Thursday. Strong subsidence and rising 500
mb heights will drive daytime highs 5 to 10 degrees above
seasonal averages. Valley locations across the Snake Plain and
Magic Valley will widespread reach the upper 70s to lower 80s
starting Thursday, with similar warm readings persisting right
through the weekend.

High confidence continues for this ridge-dominated regime to
remain locked in place through the first few days of October and
likely into the first full week of the month. Ensemble clusters
show no indication of any troughs or cold fronts capable of
breaking down the ridge. Consequently, dry conditions and above-
normal temperatures will prevail across the region, with no
true fall-like weather or widespread precipitation expected
anytime soon.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 513 PM MDT Tue Sep 29 2026

Expect VFR conditions through the period. High pressure is
building into the area and will bring mostly clear skies.
Winds remain a bit more elevated than usual overnight near BYI,
but elsewhere they should be light and variable overnight. Winds
will gust near 15kts for most sites tomorrow afternoon. No
precipitation is expected through the rest of this week.

&&

.FIRE WEATHER...
Issued at 100 PM MDT Tue Sep 29 2026

High pressure is building in over the area and will allow us to warm
up and dry out for the rest of the week. Winds will still be a bit
breezy at times today and tomorrow with gusts around 20 to 25 mph,
especially in the eastern Magic Valley and South Hills. Temperatures
continue to warm through the week and eventually highs in the lower
elevations will push towards 80 degrees, running about 10 degrees
above our climatological normals for this time of year which are
generally in the upper 60s and low 70s. Each afternoon, min RHs will
range from 20 to 35 percent. Both the 6 to 10 and 8 to 14 day
outlooks continue to show a high probability of continued above
normal temperatures and below normal precipitation through the first
two weeks of October.

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...McKaughan
AVIATION...TW
FIRE WEATHER...AMM