829
FXUS65 KPIH 140433
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
1033 PM MDT Thu Aug 13 2026

.KEY MESSAGES...

- Active Burn Scar Flash Flood Threats: Heavy rainfall has
  triggered a Flash Flood Warning for the Big Rock Burn Scar
  today. A Flash Flood Watch will take effect Friday afternoon
  through Saturday evening for the Wapiti Burn Scar due to
  lingering monsoonal moisture.


- Unseasonably Cool and Unsettled Through Saturday: Waves of
  monsoonal moisture in southwesterly flow will keep
  temperatures well below normal with periodic widespread
  showers and embedded thunderstorms.


- Drying & Moderating Trend Next Week: A drier pattern takes
  hold Sunday into early next week. Daytime highs will recover
  into the lower 80s, though isolated afternoon pop-up storms
  remain possible.

&&

.DISCUSSION...
Issued at 232 PM MDT Thu Aug 13 2026

Afternoon satellite imagery reveals widespread mid-level
cloudiness across eastern Idaho as the region remains embedded
in a moist, southwesterly flow regime. Widespread showers with
embedded thunderstorms continue to move through, delivering
beneficial wetting rainfall across much of the area. The primary
operational impact today is heavy rain over recent burn scars;
a Flash Flood Warning remains in effect for the Big Rock Burn
Scar, where heavy rainfall has already produced active flooding.
Outside of the burn scar, rainfall totals have been more
modest. Temperatures are substantially colder than 24 hours ago,
with much of the region currently sitting in the 60s under
cloud cover and precipitation. High-resolution convective-
allowing models (CAMs) indicate another surge of moisture
through late evening before activity diminishes overnight to
isolated or scattered coverage.

A second, weaker shortwave impulse arrives from the southwest
on Friday. Because this system lacks the strength of today`s
disturbance, convective coverage will be less widespread.
Guidance heavily favors the central mountains and higher terrain
closer to the storm track, though showers and isolated storms
remain likely across lower valley zones. With monsoonal moisture
remaining entrenched, locally heavy rainfall will stay a
threat, prompting a Flash Flood Watch for the Wapiti Burn Scar
starting Friday afternoon and continuing through Saturday
evening.

On Saturday, one final shortwave disturbance tracks through the
region as upper-level flow flattens from southwesterly to
westerly. Model guidance has trended higher with precipitation
probabilities (PoPs) area-wide, making another day of scattered
to widespread showers and thunderstorms likely regionwide. The
central mountains remain the primary target for storm activity,
and a localized flash flood threat could linger through
Saturday. Temperatures throughout this period will remain well
on the cool side of normal under persistent cloud cover and
rain.

A transition toward drier conditions takes hold Sunday into
early next week, though residual low- and mid-level moisture
will linger. Because the ridge cap building over the region is
unlikely to be strong enough to completely suppress convection,
isolated diurnal (heat-of-the-day) pop-up thunderstorms are
expected each afternoon and evening. Daytime highs will moderate
back into the lower 80s by next week, remaining just a few
degrees below seasonal averages.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1019 PM MDT Thu Aug 13 2026

Yet another round of thunderstorms with heavy rainfall
accumulations expected. Light precipitation is expected during
the overnight hours, with more steady SHRA developing in the
late morning. By 14/18Z TSRA should be developing. The
atmosphere is expected to be more unstable, so outflow should be
stronger than Thu. Marginal VFR CIGs and VSBYs are possible
with these thunderstorms, although mainly limited to KIDA, KPIH,
and KDIJ. The showers will shut off during the early evening,
with some rapid clearing.

Wind should stay light, except in the vicinity of TSRA.

&&

.FIRE WEATHER...
Issued at 230 PM MDT Thu Aug 13 2026

Red flag warnings remain in effect through 9 pm this evening
for scattered thunderstorms. Will see isolated to scattered
showers and thunderstorms again Friday but not as widespread and
have no red flag warnings in effect Friday based on coverage
witnessed this afternoon.

&&

.PIH WATCHES/WARNINGS/ADVISORIES...

&&

$$

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