908
FXUS65 KPIH 282239
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
439 PM MDT Mon Sep 28 2026

.KEY MESSAGES...

- Isolated Late Afternoon/Evening Storms East of I-15:
  Lingering cloudiness and weak shortwave energy will spark
  isolated showers and a stray thunderstorm late this afternoon
  and evening, primarily focused east of the I-15 corridor.

- Seasonable Temperatures Early This Week: High temperatures
  Monday through Wednesday will hover near seasonal averages,
  reaching the upper 60s to lower 70s across lower elevations.

- Unseasonably Warm Early October: Upper-level ridging builds
  over the Intermountain West starting Thursday, bringing high
  confidence in dry weather and temperatures 7 to 10 degrees
  above normal (mid-to-upper 70s, with localized spots touching
  80F).

&&

.DISCUSSION...
Issued at 127 PM MDT Mon Sep 28 2026

Cloud cover continues to gradually decrease from west to east
across the region this afternoon as a weak low-pressure system
positioned to our south loses its influence on eastern Idaho`s
weather. Lingering moisture and cloudiness remain anchored over
far eastern and southeastern zones. High-resolution convective-
allowing models (CAMs) indicate sufficient instability to
generate isolated showers and perhaps a stray thunderstorm later
this afternoon and evening, generally focused east of the I-15
corridor. Precipitation chances will diminish rapidly late this
evening, becoming non-existent by midnight as atmospheric drying
takes hold. Overnight lows will remain seasonably cool under
clearing skies.

A broad, tranquil weather regime takes over across eastern
Idaho for the first half of the workweek. With the departing
system well to the south and high pressure beginning to
organize to the west, precipitation chances remain near zero.
Daytime high temperatures Tuesday and Wednesday will hover right
around late- September climatological norms, topping out in the
upper 60s to lower 70s across lower-elevation valleys.

Confidence remains very high in a prolonged dry and unseasonably
warm weather pattern developing Thursday and extending into the
first week of October. Global model ensembles are in strong
agreement that an upper-level ridge will build directly over the
Intermountain West on Thursday and remain anchored over the
region through the weekend. Rising 500 mb heights and subsidence
will drive a noticeable warming trend, pushing daytime maximum
temperatures 7 to 10 degrees above seasonal averages. Lower-
elevation valleys will widespread reach the mid-to-upper 70s
starting Thursday, with localized spots likely topping 80F
during peak diurnal heating. Given the strength and positioning
of the ridge, measurable precipitation is highly unlikely
through the upcoming weekend and likely through much of the
following week as well.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 439 PM MDT Mon Sep 28 2026

A stray shower could approach IDA/DIJ this evening, but looking
at minor or no impacts. Skies should clear everywhere tonight.
Winds should go light most places.

&&

.FIRE WEATHER...
Issued at 127 PM MDT Mon Sep 28 2026

Upper level low and troughing continue to move eastward through the
rest of today and tonight. This keeps most of the shower and
isolated thunderstorm activity confined to the eastern and
southeastern Highlands, but some isolated activity continues in the
Central Mountains through the evening. By tomorrow afternoon, weak
high pressure begins to build back in over the area and a slow,
modest warming trend starts. Highs on Tuesday will generally be in
the upper 60s to low 70s across the area with afternoon wind gusts
around 15 to 20 mph with gusts to 25 mph in parts of the South Hills
and eastern Magic Valley. Min RHs will be drier on Tuesday, ranging
from the mid 20s to low 30s through most of the eastern Magic
Valley, South Hills, Central Mountains, and Snake River Plain.
However, moisture lingers a bit longer in the east with min RHs
around 35 to 40 percent. Throughout most of the week, expect
afternoon RHs to range from 20-35 percent and highs will peak on
Friday with the lower elevations make it back into the upper 70s and
low 80s, which is about 10 degrees above our "normals" for this time
of year. After our precipitation today, the rest of the week looks
dry.

&&

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

&&

$$

DISCUSSION...McKaughan
AVIATION...13
FIRE WEATHER...AMM