169
FXUS65 KPIH 301134
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
534 AM MDT Sun Aug 30 2026

.KEY MESSAGES...

- Pleasant Post-Frontal Sunday: Early morning showers are
  pushing east into Wyoming, clearing the way for widespread
  midday sunshine, cooler high temperatures in the upper 60s to
  mid-70s, and breezy afternoon conditions (gusts up to 30 mph
  across the Arco Desert and upper Snake Plain).

- Chilly Sunday Night: Light winds, clear skies, and a drier
  air mass will allow overnight lows to drop into the 40s in
  lower elevation valleys and 30s across high country basins.

- Unsettled Workweek Waves: Embedded shortwaves within a broad
  Pacific trough will bring shower and thunderstorm chances to
  the eastern highlands on Monday, shifting toward the Central
  Mountains and Continental Divide on Tuesday.

- Breezy & Seasonably Cool Mid-to-Late Week: An upper-level low
  anchored near Vancouver Island will maintain near to slightly
  below-normal temperatures, with tightening pressure gradients
  causing periodic breezy days Wednesday through Friday.

&&

.DISCUSSION...
Issued at 140 AM MDT Sun Aug 30 2026

Early morning radar imagery indicates the final showers and
embedded thunderstorms are exiting eastern Idaho into western
Wyoming. While high-resolution convective-allowing models (CAMs)
maintain low-end shower chances through daybreak, precipitation
chances will diminish rapidly across the forecast area.
Widespread sunshine will overspread the region by midday as a
cooler, drier post-frontal air mass builds in. Daytime maximum
temperatures will top out in the upper 60s to mid-70s, making
for a pleasant late-August afternoon. The post-frontal surface
pressure gradient will support breezy afternoon winds of 15 to
20 mph with gusts up to 30 mph, particularly across the upper
Snake Plain and Arco Desert. Dry conditions will prevail
tonight. Clear skies and efficient radiational cooling will
drive overnight lows into the 40s across lower elevation
valleys, while high-altitude basins fall into the 30s.

Eastern Idaho will remain under the influence of a broad upper-
level trough anchored over the Pacific Northwest through early
next week. Multiple waves of shortwave energy embedded within
this southwesterly-to-westerly flow will cross the region. The
first impulse tracks across the area on Monday, bringing
isolated to scattered shower and thunderstorm chances primarily
to the eastern half of Idaho. A secondary, more robust shortwave
approaches western Idaho on Tuesday, elevating precipitation
probabilities across the Central Mountains and northward toward
the Montana Divide. Afternoon maximum temperatures will hold
near seasonal norms in the 70s to lower 80s.

By mid-to-late week, global ensemble guidance locks a broad
upper-level cyclone near Vancouver Island, keeping persistent
cyclonic flow across the Intermountain West. Periodic shortwave
impulses rotating around the parent low will track through the
Pacific Northwest. Current guidance suggests the bulk of deep
atmospheric moisture will stay shunted north and west of eastern
Idaho from Wednesday through Friday, though localized mountain
showers remain possible. Model variance increases significantly
regarding the exact strength, track, and timing of these
individual shortwaves. These subtle spatial differences will
ultimately dictate local daily wind speeds, cloud shading, and
precipitation coverage. Tightening pressure gradients ahead of
incoming impulses will likely result in several breezy afternoon
periods. For now, National Blend of Models (NBM) guidance
maintains afternoon temperatures at or a few degrees below
seasonal averages through next weekend.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 529 AM MDT Sun Aug 30 2026

VFR conditions expected through the period with gradually
clearing skies today and no precipitation. Winds will be breezy
today though with gusts upwards of 25 kts, at times, especially
around KIDA and KPIH. Winds will lessen later this evening with
SKC conditions likely for the overnight.

&&

.FIRE WEATHER...
Issued at 140 AM MDT Sun Aug 30 2026

A drier post-frontal air mass will yield lower afternoon
relative humidity values today, dropping minimum RH briefly
below 15% across lower elevations of the Arco Desert and into
the central mountains. Combined with afternoon wind gusts of 20
to 30 mph across the Arco Desert and Snake Plain, localized
elevated fire weather conditions will exist briefly this
afternoon. Excellent relative humidity recoveries are expected
tonight as temperatures drop into the 30s and 40s. Moisture
increases modestly Monday and Tuesday with passing shortwaves,
bringing scattered wet/dry storm chances to the eastern and
central mountains. Breezy conditions persist mid-to-late week
under broad troughing, but relative humidity values will remain
generally above critical thresholds.

&&

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

&&

$$

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