416
FXUS65 KPIH 030045
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
645 PM MDT Wed Sep 2 2026

.KEY MESSAGES...

- Showers and a few thunderstorms possible through Saturday
  mainly across the central mountains

- Breezy conditions across the rest of eastern Idaho through
  Friday

- Shower and thunderstorm chances increase as low pressure
  interacts with moisture from Marie with the question being how
  much of moisture from this tropical low impacts eastern Idaho

&&

.DISCUSSION...
Issued at 1143 AM MDT Wed Sep 2 2026

Showers and storms continue to quickly exit the central
mountains this afternoon, with a few other showers and storms
trying to form east of I-15 in the mountains. The latter area of storms
should remain isolated with coverage remaining under 15%. The
bigger story is cooler temperatures and wind behind the cold
front. Gusts will continue to flirt with LAKE WIND ADVISORY
criteria on American Falls Reservoir and WIND ADVISORY from
Craters through Monida Pass. For now, it looks like the
potential is too low and not widespread enough to issue any
headlines. Some folks have likely already seen highs for the
day, or will be back within a couple of degrees of where they
were ahead of the front. Afternoon temperatures in the central
mountains should remain in the 50s and 60s, with 60s and 70s
elsewhere. Parts of the Stanley Basin may struggle to get above
50. Starting tonight and continuing through Saturday, any
potential for showers and storms should remain mostly over the
central mountains. We may see a few light showers and a few
storms during that period across the rest of eastern Idaho, but
this should be very limited in terms of time. Otherwise, it will
remain breezy through Friday. Gusts will be lighter than today,
but still 25-35 mph at times...maybe pushing 40 mph in a few
spots. Highs will slowly creep back up, but most of the time
remaining in the 60s and 70s. A few low 80s may pop up on a
thermometer across portions of the Snake Plain, Magic Valley,
and valleys closer to the Utah border on Saturday.

Showers and storms increase areawide Sunday and Monday. Low
pressure that will have been setting to our northwest swings
farther inland and to our northeast. This will draw moisture
from the southwest, and try to tap into moisture from eventual
Hurricane Marie off the coast of Baja. The question is how much
will make it into Idaho. Trends this week have been 1)to keep
the low itself across the Pacific and not drawn into low
pressure across the western states, and 2) shunt most of the
moisture across Utah, Wyoming, and Colorado. There continues to
be fluctuations daily with the official forecast (WPC-based) for
precipitation. Compared to 24 hours ago, the forecast has
doubled (nearly tripled) for Sunday and Monday. The latest has
0.25-0.50" for the Snake Plain and Magic Valley, and 0.40-0.90"
for higher elevations (highest across the eastern and southeast
highlands). The placement of higher amounts seems reasonable due
to trending more south and east with the main push of moisture
from Marie. The amounts seem overdone based on the trends we
mentioned. When looking at the raw Blend of Models "middle of
the road" forecast, it is showing 0.10-0.33" for the Snake Plain
and Magic Valley and 0.25-0.75" for the mountains with locally
higher amounts. This seems more reasonable and also what
previous WPC-based forecasts looked like. The higher end of the
forecast range shows widespread 1"+ amounts except for the Magic
Valley which is still 0.75-1.0". Considering the trends, that
would definitely fall under "low probability/high impact". Even
if we see less cloud cover and precipitation, we will stay
cooler overall. Stay tuned.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 643 PM MDT Wed Sep 2 2026

Expect mostly vfr ceilings tonight with winds quickly weakening
this evening. Expect most showers tonight to fall in the way of
virga. Some showers may encroach upon SUN tonight but should
not provide much impacts.

&&

.FIRE WEATHER...
Issued at 1143 AM MDT Wed Sep 2 2026

The threat of showers and storms across the central mountains is
almost over, as the bulk of this has shifted into Montana. The
tail end of this should clear the state by mid afternoon. We
will go ahead and end the RED FLAG WARNING for Zone 422 early. A
few other showers and storms are possible mainly east of I-15
and actually mostly like east of the state through this
afternoon. Otherwise, it will be breezy with near-critical or
locally critical fire conditions across the rest of eastern
Idaho. Humidity should hold around 15% or higher where drier air
has moved in. Gusts of 25-45 mph are expected through this
evening. The bulk of any showers and thunderstorms through
Saturday will be across the central mountains, closer to low
pressure settling in along the coast, and where moisture will
persist. There will be the potential for a few showers or storms
elsewhere, but any widespread or prolonged potential isn`t
there. The trend for breezy conditions will remain with gusts
25-35 mph at times. Lower humidity for Thursday will confined to
mainly the southeast corner across Zone 413, and still limited
to 15% or higher. Humidity will rise Friday and Saturday and not
be an issue.

Showers and thunderstorms increase Sunday and Monday. The
question becomes how much moisture will fall, which is
dependent on Hurricane Marie. The latest "official forecast"
calls for 0.25-0.50" for Zones 410 and 425. The rest of central
and eastern Idaho would see 0.40-0.90". This is a huge increase
from previous forecasts, 0.10-0.33" and 0.25-0.75",
respectively. The raw Blend of Models "middle of the road
forecast" basically shows the latter set of amounts. The higher
end of the Blend has more widespread 1"+ amounts with 0.75-1.0"
for the Magic Valley (Zone 425). The trends AWAY for deeper
moisture from Marie would suggest these higher end amounts have
a low probability of occurring. The more likely forecast seems
to be the "middle of the road" forecasts from the Blend. We will
likely continue to see fluctuations in the amounts until the
models get a better handle on where most of the moisture of
Marie ends up traveling across the southwest U.S.

&&

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

&&

$$

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