490
FXUS65 KPIH 291225
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
625 AM MDT Sat Aug 29 2026

.KEY MESSAGES...

- Marginal Severe Risk Area-Wide Today: Nearly all of eastern
  Idaho remains under a Marginal Risk for severe thunderstorms
  today, while the Slight Risk zone has shifted south into
  Northern Utah. Strong shear will remain capable of producing
  isolated damaging wind gusts and small hail within stronger
  cells.

- Showers Persist Into Early Sunday: High-resolution model
  guidance keeps shower and thunderstorm activity around
  throughout the day today and through the first half of Sunday
  morning before rapid clearing takes hold Sunday afternoon.

- Slight Warming Trend Next Week: Daytime high temperatures next
  week have been adjusted slightly upward compared to previous
  forecasts, returning lower-elevation values closer to seasonal
  averages in the upper 70s and 80s.

&&

.DISCUSSION...
Issued at 258 AM MDT Sat Aug 29 2026

Eastern Idaho remains positioned under broad southwesterly flow
between an upper-level low moving through the Pacific Northwest
and high pressure anchored over the South-Central U.S. The
latest convective outlook update has shifted the Slight Risk
area south into Northern Utah, where low-level moisture and
instability are most favorably aligned. However, nearly all of
eastern Idaho remains under a Marginal Risk today. Effective
bulk shear values exceeding 40 knots will remain sufficient to
organize terrain-forced convection, making localized severe
downburst winds (50-60+ mph) and small hail the main threats
with stronger cores.

High-resolution convective-allowing models (CAMs) are in strong
agreement that shower and thunderstorm coverage will persist
throughout the day today and linger through tonight. Unlike
typical diurnal events that collapse quickly after sunset,
elevated moisture and synoptic lift will keep precipitation
active into the early morning hours of Sunday.

As the primary upper trough axis pivots eastward across
northern Montana and southern Alberta on Sunday, drier air will
shunt into the region from the west. Showers and cloud cover
will linger through Sunday morning, particularly over the
Eastern Highlands, before a steady clearing trend takes hold
from west to east during the afternoon hours. Temperatures on
Sunday will remain on the cool side of average, holding in the
upper 60s and 70s across most valley locations.

A transitional pattern takes shape for the new workweek as weak
ridging attempts to build into the Great Basin. Forecast
guidance has nudged daytime temperatures slightly upward
compared to yesterday`s model runs, pushing lower-elevation
highs back into the upper 70s to lower 80s through the week.
However, operational models and ensemble clusters continue to
exhibit significant spread regarding the long-range upper-level
pattern. Guidance is struggling to resolve how quickly secondary
shortwave energy moving out of the Gulf of Alaska will flatten
the ridge or re-establish broad Pacific Northwest troughing.
Given this variance, a consensus blend remains the preferred
forecast approach, keeping low-end, isolated afternoon mountain
storm chances and near-normal temperatures in place through the
second half of next week.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 618 AM MDT Sat Aug 29 2026

Will continue to see showers and thunderstorms across the region
through Saturday evening with precip gradually tapering off from
west to east as we move into the early morning hours on Sunday.
Maintained PROB30 groups for later this afternoon to account for
TSTM and gusty wind potential. CIGs should remain at VFR levels
through the period despite the storms around the area.

&&

.FIRE WEATHER...
Issued at 258 AM MDT Sat Aug 29 2026

Extensive cloud cover, surging relative humidity, and widespread
precipitation will keep fire weather concerns heavily suppressed
through Sunday morning. While lightning frequency will remain
elevated with passing convective cores today and tonight, rain
efficiency will keep most storms wet. Gusty and erratic outflow
winds up to 45 mph remain the main operational hazard with
stronger cells today. Clearing conditions Sunday afternoon will
lead into a slight warming trend next week, though relative
humidity values will remain at or above critical thresholds.

&&

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

&&

$$

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