675
FXUS65 KPIH 152239
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
439 PM MDT Mon Sep 15 2025

.KEY MESSAGES...

- Shower and thunderstorm potential decreasing through Tuesday
  evening

- Dry weather for midweek until the weekend

- Warmer afternoon temperatures return under high pressure

&&

.UPDATE....
Issued at 438 PM MDT Mon Sep 15 2025

Latest guidance indicates that the northeast winds
may be a touch stronger with a few gusts possible over the American
Falls reservoir. So will issue a lake wind advisory for tomorrow
afternoon, with rough chop likely especially near the dam.

.SHORT TERM /THROUGH TUESDAY NIGHT/...
Issued at 103 PM MDT Mon Sep 15 2025

As low pressure slowly departs to the northeast in the next 24
hours, pockets of showers and isolated storms will
persist...especially into tonight. The best chances will remain
across portions of the central mountains, upper end of the Snake
Plain and eastern highlands. A brief burst of rain is possible.
Right now, any risk of small hail and stronger wind is slim to
none. Coverage dwindles from southwest to northeast. We may see
an additional band develop along a windshift dropping southwest
across our area overnight. On Tuesday, some wraparound showers
with a rumble of thunder possible are expected along the Montana
and Wyoming borders. That will quickly end tomorrow evening.
Temperatures will be at to just below average both in the
morning and afternoon.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 103 PM MDT Mon Sep 15 2025

Wed through next Mon night. The upper level pattern is
very weak through Sat in the western states, with the ridge sitting
over the Great Basin. This should allow a warming with a dry pattern
through that period. Afternoon temperatures continue to be above
climatic normals for this time of year. The weak pattern means
little to no wind with no feature moving through. The only fly in
the ointment is that such a weak pattern could allow moist and
unstable air from the Gulf of California to make its way into
southern Idaho. However, the NBM is indicating precipitation
probabilities at 10 percent of below for the moment.

On Sun, a very weak upper level trough moves through southern Canada
for two clusters making up 49 percent of the solutions with 26
percent having this trough dig far enough south to perhaps bring
clouds, precipitation, and unstable air. For Mon, about 40 percent
of the solutions continue to have low pressure over some part of
southern Canada. The end of this period has a much faster and more
zonal flow that the weak flow of the first half. Thus the weather at
the end may be more determined by the progression of shortwaves
through this mean flow, and makes the forecast more uncertain for
Sun and Mon. This risk falls out in the 10 to 25 percent range of
probability, so the slight chance risk appears validated for now.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 437 PM MDT Mon Sep 15 2025

Models show a stray shower still possible around
SUN/IDA/DIJ early this evening. Otherwise, should mostly clear out
quickly this evening. Should lose wind gusts early this evening as
well.

&&

.FIRE WEATHER...
Issued at 103 PM MDT Mon Sep 15 2025

Warming and drying will return to the forecast area
as high pressure moves in behind the low that generated showers and
thunderstorms this previous weekend. High pressure remains through
Sat afternoon, allowing temperatures to continue above climatic
normals and for humidity to be lower than usual, with some lower
elevation humidity lowering below 15 percent by Fri. The warmer
conditions will be offset by the stabilizing high pressure for
instabilities to remain about the same every afternoon. The very
weak high pressure pattern after today should keep wind away from
critical thresholds and the sunshine produce normal slope-valley
interactions. The next risk of precipitation and convection is not
really until Sun at the earliest.

&&

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

&&

$$

UPDATE...13
SHORT TERM...Keyes
LONG TERM...Messick
AVIATION...13
FIRE WEATHER...Messick