804
FXUS65 KPIH 230320
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
920 PM MDT Tue Sep 22 2026

.KEY MESSAGES...

- Showers and thunderstorms ending overnight west to east with
  brief downpours expected

- Warmer temperatures through Friday

- Breezy Friday afternoon followed by cooler weather this
  weekend with some potential for showers and storms

&&

.DISCUSSION...
Issued at 1105 AM MDT Tue Sep 22 2026

Low pressure will continue shift northeast across Utah, Idaho,
and Wyoming through tonight. Stronger showers and storms will
produce heavier downpours, with the potential for 0.10"-0.20" in
those situations or where multiple showers/storms move over the
same location. The potential for anything over 0.20" is 30-60%,
but that is not widespread and fits with the idea of
showers/storms vs widespread precipitation. There isn`t too
much potential for gusty outflow winds, generally 10% or less,
except around Bear Lake where the potential is pushing 50%
through midnight.

We go back to dry and warmer conditions through Friday morning.
Highs quickly bounce back into the 70s with some lower 80s mixed
in Thursday and Friday. Friday into Saturday, low pressure
swings by to our northwest. We should see some light rain showers
and storms across the central mountains, but the main hazard
will be stronger winds across all of central and eastern Idaho.
Gusts of 20-35 mph will be common across the entire area, with
some gusts around 40 mph possible across the Arco Desert,
central mountains and along the Montana border. Saturday and
beyond is a mess forecast-wise. The ECMWF continues to show a
weaker low crossing Idaho early next week. The GFS wants to
develop split flow and drag the low farther south. The caveat
with the latest version of that model is that it`s still far
enough north to keep showers and storms in the forecast, AND
also wants to clip the state with deeper tropical moisture from
the Pacific. This would be coming from Hurricane Polo IF this
pattern pans out. Needless to say, there potential forecast
ideas is pretty wide ranging. The Blend of Models shows a
gradual increase in showers and storms during that timeframe,
which seems perfectly reasonable. Temperatures after Friday
remain cooler, with valley highs in the 60s and lower 70s.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 920 PM MDT Tue Sep 22 2026

Main concern overnight is low stratus and fog formation which
the HRRR indicates could develop along the Snake River which
could impact IDA, PIH and BYI. The NBM shows this developing as
well. With light winds, cool temperatures and plenty of moisture
around, fog is a strong possibility. Very uncertain on timing
of when it would develop. Need cloud cover associated with the
upper low to exit the TAF sites. So most likely late in the
night, perhaps as late as 12z.


&&

.FIRE WEATHER...
Issued at 1105 AM MDT Tue Sep 22 2026

Showers and storms will continue into tonight, ending from west
to east. Stronger showers and storms, or multiple storms over a
given location, may produce 0.10-0.20". There is a 30-60% chance
for higher amounts, BUT it would be spotty based on the pattern.
We return to dry and warmer conditions quickly, and continuing
through a good part of Friday. Low pressure swings by to our
northwest, producing a few light showers and storms over the
central mountains. The bigger impact will be increasing winds
across the area. Wind gusts of 20-40 mph are expected, strongest
across the Snake Plain (Zone 410), the central mountains
(422/475/476) and along the Montana border in Zone 411. Humidity
values at the moment should stay above 20% based on the current
forecast trends. We do expect another round of showers and
storms early next week. The question is will it be with a weaker
low moving across Idaho, or with a deeper and slow low clipping
us from the south. The latter idea also tries to pull in better
moisture from Hurricane Polo, but even that current forecast
only clips the state with the deeper moisture and keeps most it
farther south and east.

&&

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

&&

$$

DISCUSSION...Keyes
AVIATION...13
FIRE WEATHER...Keyes