333
FXUS65 KPIH 311016
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
316 AM MST Fri Jan 31 2025

KEY MESSAGES:

- A major change to our cold and dry pattern moves in today
  through the weekend as a multi-day atmospheric river brings a
  return to widespread precipitation.

- Precipitation is expected to remain mostly snow with this event
  with a rain/snow mix possible across our lowest elevations.

- Winds are expected to increase later today into tonight, peaking
  on Saturday, before subsiding Saturday night into Sunday.

- Precipitation chances will continue each day into early next
  week with extensions of current winter products possible.

&&

.SHORT TERM...Today through Saturday Night.
Following several weeks of quiet and dry weather across SE Idaho,
a multi-day atmospheric river event is expected to begin later
today and continue through the weekend into early next week as
widespread precipitation returns to our region. GFS/ECMWF model
IVT and IWV forecasts remain in solid agreement on the location
and duration of this atmospheric river with high confidence
supporting multiple days of widespread precipitation. The onset of
precipitation today will be west to east, beginning around midday
in the ERN Magic Valley and CNTRL Mountains before expanding to
ERN Idaho through the afternoon and evening hours. The bulk of
precipitation with this first organized push of moisture remains
favored to be all snow outside of a rain/snow mix potential across
the Lower Snake River Plain and ERN Magic Valley where we could
also see pockets of freezing rain at times. Winds will begin to
increase later today into tonight and continue through Saturday
with wind gusts of 35 to 45 mph leading to areas of blowing and
drifting snow ahead of winds beginning to gradually subside
Saturday night into Sunday. Have added the mention of this

Our latest hazards over the next 48 hours remains in similar
shape to previous forecasts with a mix of Winter Storm Warnings
and Winter Weather Advisories. The only change made this morning
was an upgrade for the Teton Valley to a Winter Storm Warning to
capture the strong winds expected. This area around the US-26 and
ID-31/32/33 corridors are where we are expecting the strongest
winds with gusts up to 50 mph possible. While the CNTRL Mountains
are expected to see a more well defined break Saturday evening,
winter products further SE may need to be extended further into
Sunday and Monday to capture prolonged impacts of atmospheric
river moisture into our area. More on that below. You can find our
latest expected, low-end, high-end, and probabilistic forecast
snow information at weather.gov/pocatello/winter. MacKay

.LONG TERM...Sunday through next Friday.
Our multi-day atmospheric river event will continue for Sunday
into early next week with widespread snow and a mix of rain/snow
across our lowest elevations expected through at least midweek
next week as winds subside from their peak on Saturday. This is
again supported by the latest GFS/ECMWF IVT/Iva forecasts which
show a steady SW stream of moisture building into SE Idaho.
Transport of more mild air from the Pacific will lead to rising
snow levels early next week, continuing to support a mix of
rain/snow across our lowest elevations further south with
predominant snow favored further north. Our region will be caught
between above normal temperatures to our south and below normal
temperatures to the north, leading to near normal to above normal
temperatures with highs Sunday through Wednesday in the 30s/40s
and lows in the 20s/30s. Additional winter weather products are
likely needed to capture continued snow impacts which will  be
evaluated heading into this weekend over future shifts.

Increased uncertainty surrounds exactly how our pattern will
change midweek with diverging solution on exactly where this
atmospheric river moisture ends up shifting to. The NBM shows
colder and drier conditions with more isolated to scattered
precipitation chances returning for Thursday and Friday, in line
with the GFS which tries to bring in a ridge of high pressure in
and shift any AR moisture further south. In contrast, the ECMWF
model delays that drying trend by at least a few days towards next
weekend. We will continue to see exactly how the forecast trends
for next week in the coming days but in the meantime, we will keep
with our active and wet pattern into early next week. MacKay

&&

.AVIATION...12Z TAFS through 12Z Saturday.
VFR and dry conditions Friday morning will give way to a mix of
rain and snow showers building in west to east throughout the
daytime hours as a multi-day atmospheric river event moves into
SE Idaho. Increasing mid/upper-level clouds will gradually lower
throughout the day with a mix of MVFR/IFR CIGS/VIS expected as
precipitation moves on station. Predominant snow is favored at
KIDA, KSUN, and KDIJ with a rain/snow mix possible at KPIH and
KIDA. Associated with moderate to heavy bands of snow at times,
IFR/LIFR CIGS/VIS will be possible. Light winds this morning will
increase throughout the day into tonight (primarily outside of
KSUN) where they will peak on Saturday before decreasing for
Sunday. Rain/snow chances will then continue into the weekend as
our active weather pattern continues. MacKay

&&

.AIR QUALITY...
An Air Quality Advisory remains in effect for Power, Bannock, and
Bingham counties through early today. Stagnant air is leading to
degraded air quality that is unhealthy for sensitive groups.
Improvement is expected today as we begin to see increasing winds
and precipitation building in with our next system. MacKay

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 11 AM this morning to 5 AM MST
Sunday for IDZ051>057-059.

Winter Storm Warning from 11 AM this morning to 5 AM MST Sunday
for IDZ058-060>066.

Winter Weather Advisory from 11 AM this morning to 5 PM MST
Saturday for IDZ069.

Winter Storm Warning from 11 AM this morning to 5 PM MST
Saturday for IDZ071>075.

&&

$$