075
FXUS65 KPIH 012359
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
459 PM MST Mon Dec 1 2025

.KEY MESSAGES...

- Light snow or snow showers will spread across East Idaho
  tonight and continue through Tuesday night. Winter driving
  conditions are expected, especially over mountain passes.

- Daytime highs Tuesday in some lower elevations may limit
  snowfall accumulation potential, and snow may mix with rain in
  some areas.

- The next winter storm arrives Friday and continues into the
  weekend, bringing mountain snow and low elevation rain and
  snow.

&&

.SHORT TERM /THROUGH TUESDAY NIGHT/...
Issued at 126 PM MST Mon Dec 1 2025

Satellite imagery shows broad area of stratus across East Idaho
beginning to be overtopped by moisture moving in ahead of
shortwave crossing the Seattle/Vancouver area this afternoon.
Seeder-feeder light snows may begin late this afternoon and
evening ahead of main precipitation where the low clouds still
persist, but early accumulations due to this should remain very
light. High-res models remain consistent on timing of bringing
light snow into areas along the Montana border including Island
Park this evening, then slowly expanding precipitation across
the remainder of East Idaho tonight into Tuesday. Given the
northwest flow aloft, the bulk of the precipitation through the
event should be focused across the eastern and southern
highlands, with some shadowing expected across northwest
portions of the Snake Plain. Temperatures daytime Tuesday could
be warm enough across the Magic Valley and Raft River regions to
support a brief mix of rain/snow during the afternoon, and will
limit accumulation potential further north in the Snake Plain.
Total accumulations remain similar to previous forecast cycle,
generally up to an inch for most of the Snake Plain (lower in
the Magic Valley), trending toward 2-3" north toward Monida Pass
and Ashton Hill. Highland areas east of I-15 see accumulations
rise to 4-6" with locally higher amounts at and above pass
level. Further west, lesser accumulations are forecast for the
central mountains, especially for areas shadowed in northwest
flow. To the south highlands between I-84/I-86 and the Utah
border, most of the accumulation will be above valley floors,
with most mountain ranges seeing 3-5" for the event. Given these
amounts, winter headlines will NOT be issued, but motorists
could expect winter travel conditions at times through at least
Tuesday night.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 126 PM MST Mon Dec 1 2025

Will start out dry on Wednesday behind the Canadian system as it
pushes east.   It will be cool with highs in the upper 20s to mid
30s.  Going into the latter part of the week the model blends
indicate getting into a moist more zonal flow.  With that expecting
several waves of precipitation late Thursday through Sunday.  There
will be the potential for mountain snowfall accumulation in this
flow pattern.   We are likely to see substantial warming late week
into the weekend and early next week.  By Saturday snow levels will
likely rise to the 6 thousand foot level so will likely see some
rain in lower elevations with the late week and weekend
precipitation.  Grids indicating the heaviest snow in the eastern
mountains near Wyoming border Friday through Sunday.  At least a low
chance some areas above 6 thousand feet could see 6 inches but
extremely high uncertainty with any timing  and precipitation
amounts that far out into forecast period.  Friday through Monday
expect high temperatures in the 40s in low elevations and 30s to
around 40 in the mountains.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 459 PM MST Mon Dec 1 2025

Another day at the aviation desk...yet another shortwave trough
headed our way. This system will drop northwest to southeast across
our region tonight through Tuesday night. We`re having a really hard
time pinning down when and where the best periods of snow showers
will focus in relation to the airports...agreement remains poor
among high-resolution guidance and model simulated reflectivity, and
much of the system seems quite "light and showery" especially in the
CAMs. Approaching this with caution by just slowly
tapping/nudging/trending the ongoing TAF forecasts, with much of
this system currently covered with VCSHs until we can pin down
periods of potentially greater impacts at any given location.
Overall, it`s looking like any periods of lower-than-VFR cigs will
hold off until Tuesday afternoon or evening (although can`t rule out
brief MVFR if organized snow showers strike before then), and models
offer a bit more consensus on the best snow potential happening at
KDIJ so have continued with -SHSN trending -SN there starting after
06z/11pm tonight. We are seeing signs that some more significant
impacts may develop Tuesday late afternoon into late evening as
winds potentially align to generate a convergence-induced band of
snow over the Snake Plain corridor, which may impact at least KIDA,
KDIJ, and KPIH as it sinks south. Timing of this potential right now
looks like it falls after 22-23z/3-4pm, and MVFR to IFR cigs/vsbys
would be possible. We`ll be looking at this closely in future TAF
updates.

&&

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

&&

$$

SHORT TERM...DMH
LONG TERM...GK
AVIATION...KSmith