948
FXUS65 KPIH 021138
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
438 AM MST Tue Dec 2 2025

.KEY MESSAGES...

- Light snow returns during the day and continues into the night
  for most.

- After a break Wednesday, light snow with occasional periods of
  rain returns Wednesday night and continues on and off through
  the weekend.

- Windy to very windy conditions probable Friday afternoon
  through Saturday night for the Snake River plain.

&&

.SHORT TERM /THROUGH THURSDAY NIGHT/...
Issued at 134 AM MST Tue Dec 2 2025

There is a brief break from precipitation for some this morning,
but the snow and rain mixed with snow returns for the afternoon
and continues through the overnight hours. Snake River plain in
the Interstate 15/86 corridor can expect a half of an inch to an
inch in the populated areas from American Falls to Rexburg.
North of Rexburg, the snow accumulation increases rapidly to
near 2 inches in St Anthony. Very limited areas in the eastern
and southeastern highlands are now expected 6 inches or more for
today and tonight.

There is one proverbial fly in the ointment. A Snake Plain
Convergence Zone event is likely behind this feature that
crosses through in the mid-afternoon. Strong northerly wind will
interact with northwest to west wind from the central Idaho
mountains and the eastern Magic Valley. It appears to be a
strong northerly push that means this event will likely affect
the lower Snake River plain more than the northern end. This
could locally mean intense snowfall for a 1 to 3 hour period
during the early evening hours, around 1700 MST today. Keep an
eye out for this phenomenon if you expect to travel around this
time. It normally starts over the Mud Lake-Terreton area and
drives southward at the same time it intensifies.

Temperatures are trended warmer than the previous forecasts,
with near forty degrees F expected now in the lower Snake River
plain and upper 30s for the upper Snake River plain. Even Sun
Valley will reach 40 degrees F, much to their disliking. Behind
the feature that sweeps through in the afternoon, temperatures
will cool back to the 30s for the lower elevations. This is
likely the coldest high of the week for most locations, with a
warming trend reutrning for Thu. Coldest lows will be tonight
with widespread teens and 20s. A shift in the wind on Thu night
should allow the warming trend to start.

Wind should remain elevated and down right breezy with this
feature that may show up on Thu.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
Issued at 134 AM MST Tue Dec 2 2025

The longwave pattern is a low amplitude upper level ridge over
the Pacific Northwest and northern Rockies. For Fri, the
forecast area is at the boundary of positive height anomalies
in around 60 percent of the solutions, grouped into two
clusters, while the remainder keep it doubtful; this the
precipitation threat does continue. For Sat afternoon, this
ridge retreats to the southwest and every cluster appears to
have a risk of precipitation. By Sunday, nearly 25 percent of
the clusters have a trough moving through the northern Rockies
and bringing a much better chance of precipitation. But the
majority of the solutions continue this weak precipitation
threat keeping the forecast area at the border of positive
height anomalies with plenty of energy in the upper level stream
to support precipitation. Eastern Idaho is not under the core of
the positive height anomaly on the west coast until Mon. So the
threat of precipitation should nearly disappear for the
beginning of the work week. The good news about this upper level
northwesterly flow is that there is no closed low to dump a
bunch of snow quickly. So snow amounts should be light to
moderate, with the moderate amounts in the mountains and
highlands.

The benefit of being close to the positive height anomalies is
that this means temperatures have to be near to above normal for
afternoon highs. And the cloud cover will keep overnight
temperatures mild Sat highs in the eastern Magic Valley and
lower Snake River plain may approach 50 wet degrees F.

Wind may be the most significant impact from the impulses moving
down this northwesterly upper level flow. Wind Advisory/High
Wind Warning certainly appear very probable for Fri afternoon
through Sat night in the Snake River plain.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 430 AM MST Tue Dec 2 2025

A quiet morning for all airdromes except KDIJ where showers are
still sliding through from NW to SE across the region. However,
by 02/17Z the showers will see a resurgence as another shortwave
moves through the mean NWly flow. The showers appear to mostly
produce marginal VFR conditions, there are a few worse
conditions, mainly at KDIJ where it could produce very low VSBY
in SHSN. A round of intense showers should start moving through
the Snake River plain in the late afternoon and has the ability
to produce IFR conditions at KIDA first, then moving southward
to KPIH by late afternoon/early evening. By mid-evening, it may
even get pushed as far west as KBYI.

This northwest flow has the best possible result at KSUN. This
is downslope and should keep the airdrome in the precipitation
shadow with only a risk of light SHSN in the surrounding
mountains.

Precipitation should move out of the Snake River plain and Teton
basin sometime in the late evening. Then the worry will be BR/FG
and stratus.

&&

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

&&

$$

SHORT TERM...Messick
LONG TERM...Messick
AVIATION...Messick