253
FXUS65 KPIH 310859
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
259 AM MDT Mon Aug 31 2026

.KEY MESSAGES...

- Dry Daytime, Evening Storms: High-resolution models keep
  eastern Idaho dry through the daytime hours today. Shower and
  thunderstorm chances will hold off until early this evening,
  with precipitation potentially lingering into early Tuesday
  morning.

- Tuesday`s Focus Shifts North: A secondary weather system will
  move into western Idaho on Tuesday, shifting the best chances
  for showers and thunderstorms toward the Central Mountains
  and the Continental Divide.

- Breezy & Seasonably Cool Mid-to-Late Week: A large low-
  pressure system anchoring near Vancouver Island will keep
  persistent westerly flow over the region Wednesday through
  Friday. Expect daily breezy afternoon winds and temperatures
  hovering near or just below early September normals.

- Unsettled Labor Day Weekend: An upper-level low over the
  Pacific Northwest may bring unsettled weather for the holiday
  weekend, though forecast confidence regarding exact impacts
  and precipitation timing remains low due to high model spread.

&&

.DISCUSSION...
Issued at 257 AM MDT Mon Aug 31 2026

Following a chilly August morning where efficient radiational
cooling allowed high-altitude basins to drop into the 30s and
lower valleys into the 40s, eastern Idaho remains under the
influence of a broad upper-level trough over the Pacific
Northwest. Based on the latest convective-allowing models
(CAMs), the region will remain precipitation-free through the
daytime hours. Afternoon maximum temperatures will generally
reach the 70s to lower 80s across lower elevations. Moisture and
atmospheric lift will increase by early evening, initiating
isolated to scattered showers and thunderstorms. This activity
will primarily target the eastern half of the forecast area and
is expected to continue through the overnight hours, potentially
lingering into early Tuesday morning.

As Monday night`s precipitation clears out, a secondary,
impulse embedded within the upper flow is slated to approach
western Idaho later on Tuesday. The trajectory of this impulse
will shift the primary axis of atmospheric lift and moisture
further north. Consequently, precipitation probabilities on
Tuesday will be highest across the Central Mountains and
northward toward the Montana Divide and across the upper Snake
Plain while locations further south and east see more limited
coverage. Temperatures will remain steady in the 70s to lower
80s.

By mid-to-late week, global ensemble guidance is in good
agreement locking a broad upper-level cyclone near Vancouver
Island, maintaining persistent cyclonic flow across the
Intermountain West. Current guidance suggests the bulk of the
deep atmospheric moisture will remain shunted north and west of
eastern Idaho from Wednesday through Friday, though localized
mountain showers cannot be ruled out. Tightening pressure
gradients ahead of incoming Pacific impulses will result in
several breezy afternoon periods mid-to-late week. For now,
National Blend of Models (NBM) guidance maintains afternoon
temperatures at or a few degrees below seasonal averages through
the end of the workweek.

Looking ahead to the holiday weekend, models indicate an upper-
level low situated somewhere across the Pacific Northwest. This
pattern has the potential to bring unsettled weather and cooler
temperatures to eastern Idaho for Labor Day. However, confidence
in the exact evolution of this upper-level pattern remains low
at this time due to significant ensemble spread. We will
continue to monitor trends as the weekend approaches to refine
precipitation chances and timing.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1035 PM MDT Sun Aug 30 2026

Will have clear skies through Monday afternoon with some
increasing high clouds Monday evening. Expect mainly light winds
under 10 knots through Monday.

&&

.FIRE WEATHER...
Issued at 257 AM MDT Mon Aug 31 2026

Moisture is increasing modestly today and Tuesday as passing
shortwaves bring scattered wet and dry storm chances back to the
region. Convective-allowing models keep the area dry through the
daytime hours today, with shower and thunderstorm development
delayed until early this evening. This precipitation may linger
into early Tuesday morning, primarily across the eastern
highlands. The convective focus will then shift toward the
Central Mountains and Montana Divide on Tuesday afternoon.
Breezy conditions will develop mid-to-late week under a broad
upper-level trough, but minimum relative humidity values are
expected to remain generally above critical thresholds, limiting
widespread fire weather concerns. An unsettled but low-
confidence pattern approaches for the Labor Day weekend.

&&

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

&&

$$

DISCUSSION...McKaughan
AVIATION...GK
FIRE WEATHER...McKaughan