526
FXUS65 KPIH 211737
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
1037 AM MST Fri Nov 21 2025

.KEY MESSAGES...

- Daytime temperatures today will run about 5 degrees cooler
  than yesterday.

- Mostly dry conditions beginning today with very slight chances
  for showers along our southern border.

- Mostly dry and just a few degrees warmer for the weekend.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 205 AM MST Fri Nov 21 2025

The main focus this forecast package is the threat of dense
fog/freezing fog again this morning. We`ve already noted a few
localized observations of reduced visibility less than one quarter
of a mile and continue to monitor for coverage becoming more
widespread. Both the HRRR and NBM now feature a wide swath of
visibility below half a mile spreading eastward through the Magic
Valley and Snake River Plain through the early morning hours, while
the NAM Nest continues to model much patchier impacts. NBM
probability of visibility less than 1 mile only runs about 20 to 30
percent across the aforementioned regions, while the HREF carries
slightly higher chances of widespread visibilities below half mile.
Additionally, both models indicate widespread 100 to 300 foot cloud
ceilings. We may end up issuing a SPS or an advisory depending on
how widespread and impactful the fog becomes. Below freezing
temperatures could result in ice being deposited on roadways. Anyone
traveling now through later morning should be prepared for the
possibility of slick spots and sudden drops in visibility.

While we still stand a slight chance of a shower or two along the ID-
UT border early today, our few-day stretch of dry conditions begins
today. As the upper low along the CA coast continues tracking
southward, weak ridging will begin to build in today from the West,
resulting in fewer clouds come afternoon and a continuation of light
winds.

Daytime temperatures will run around 5 degrees cooler than
yesterday. Overnight temperatures will also decrease by a few more
degrees in most locations as we will be less insulated by clouds
tonight.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Issued at 132 PM MST Thu Nov 20 2025

Mostly quiet pattern on tap leading into the Thanksgiving holiday
for East Idaho as split flow pattern continues. Models and ensemble
clusters are in good agreement throughout. Deep low over the
southwest states ejects eastward with upper ridge for East Idaho
over the weekend. Expect mild temperatures and dry conditions. Weak
system drives through the northern stream flow on Monday. bringing a
slight chance of showers to the higher elevations Sunday night
through early Tuesday. Cold front passage associated with this
system briefly drops daytime high temperatures for Tuesday. Upper
ridge rebounds for the middle to latter half of the week, for dry
and mild conditions for Thanksgiving Day.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1037 AM MST Fri Nov 21 2025

Areas of IFR or below fog and low stratus continue this morning
mainly through the Snake Plain and adjacent valleys, though DIJ
is maintaining VFR conditions just south of the cloud edge.
Although there is some potential for brief improvement this
afternoon and early evening for BYI/IDA/PIH, persistence will be
prudent path forward. There is a small chance (15-25%) of
seeing the moisture advect north during the afternoon and
evening for SUN once the diurnal winds shift to the south, but
the downslope flow onset after 02Z should clear that back out to
VFR. The rest of the terminals can expect some combination of
fog and/or low stratus to return to IFR or lower conditions for
the remainder of the terminal period.

&&

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

&&

$$

SHORT TERM...Cropp
LONG TERM...DMH
AVIATION...DMH