464
FXUS65 KPIH 010311
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
911 PM MDT Mon Aug 31 2026

.KEY MESSAGES...

- Showers and thunderstorms will return and continue through the
  next several days

- Critical to near-critical fire conditions for thunderstorms
  expected Tuesday for thunderstorms and wind/humidity Wednesday

- Cooler temperatures expected from Wednesday onward as low
  pressure settles in across the western U.S.

&&

.DISCUSSION...
Issued at 104 PM MDT Mon Aug 31 2026

A weak "wave" will lift north across eastern Idaho
through tomorrow morning, bringing an increase in showers and
thunderstorms including a few storms overnight. The best chance of
rain will be generally east of an Oakley to Island Park line.
We may see a few light showers to the northwest of that, but chances
are currently under 20%. We could see some brief heavier downpours
farther east, especially outside of the Snake Plain.
There is a 10-50% chance of gusts over 35 mph, with high end
approaching 45 mph. By tomorrow afternoon, the next round of showers
and storms will already be developing. The bulk of this round will
initially forming across the central mountains south through the
Magic Valley and South Hills/Albion Mountains.
Expect some heavy downpours and also a 40-90% for gusts over 35 mph,
pushing 50-55 mph. This shifts quickly to the northeast tomorrow
night. As low pressure along the coast, another "wave" races north
on Wednesday. This will keep off another round of showers and
thunderstorms, with the main focus being across the central
mountains. There is a 10-40% chance of gusts over 35 mph as current
timing pushes any risk of strong/severe storms into Montana. A
couple of higher resolution models have isolated storms east of I-15
and around Island Park, but we currently have that potential under
10% in the forecast. The bigger issue will likely be increasing
winds across the entire forecast area.
The strongest winds would be across portions of the central
mountains, Arco Desert/INL and along the Montana border. We pushed
the Blend of Models forecast toward the highest end of the range
based on trends and the pattern, which puts us close to WIND
ADVISORY thresholds. Temperatures will remain in the upper 70s to
mid 80s for highs again Tuesday, but drop back into 70s, even
mid/upper 60s for higher valleys with the front on Wednesday.

Beyond that, general low pressure settles in along the coast into
early next week. Initially, showers and storms will basically
develop across the central mountains. Heading into the weekend,
showers and storms will become more widespread. The amount of
monsoon moisture does increase, so the potential for heavier
rainfall may return. Of note, although the main GFS models is an
extreme outlier, it wants to be aggressive with grabbing the
remnants of tropical development in the Pacific and pull it
north across Idaho. All other models (ECMWF and it ensembles,
the GEFS and AIGFS) do not show this at all. Either way,
temperatures look to remain cooler with highs in the 60s and
70s.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 911 PM MDT Mon Aug 31 2026

A few thunderstorms are on the leading band of moisture working
northward. Most of the thunderstorms should diminish by 06z.
Showers will pass through east Idaho overnight into Tuesday
morning. Gusty winds are likely during the overnight hours but
should relax Tuesday morning. Another round of convection is
expected Tuesday afternoon.

&&

.FIRE WEATHER...
Issued at 135 PM MDT Mon Aug 31 2026

A mass of moisture is moving in from the south, arriving in
southern Idaho in the early evening and in eastern Idaho around
midnight, and central Idaho around Tuesday morning. Thunderstorms
should develop by at least Tuesday afternoon with scattered
coverage in the central Idaho mountains and the northern end of
the Snake River plain. Red Flag Warning was issued for the
norther portions of the Sawtooth NF. The higher threat of
wetting rains in the northern half of the Snake River plain have
made the lightning activity of lower threat.

The incoming moisture will mean cloudiness that will keep
temperatures relatively cool, and thus humidity readings should
be way up, at least for a little. May have to watch Fire Weather
Zone 427 on Wed as humidity dries out first there, at the same
time as wind increase to breezy to windy conditions.

Warming and drying develop for the middle part of the week, with
Sunday being the next day of significant shower and
thunderstorms activity.

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from 1 PM to 9 PM MDT Tuesday for IDZ422.

&&

$$

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