Blizzard and Winter Storm in Idaho, January 12 to 13, 2024

Area Forecast Discussion
National Weather Service Pocatello ID
234 PM MST Thu Jan 11 2024

.SHORT TERM...Tonight through Friday Night.
We are still on track for a strong, impactful winter storm to move
into the area beginning tonight with this first "wave" lasting
through Friday. Snow showers are already ongoing across portions of
the Eastern Highlands and Southern Hills this afternoon, and winds
in some areas already gusting over 35 mph. The interaction of the
low to our north and Pacific moisture will continue to bring snow to
the area with coverage expanding tonight and into Friday. Hi-res
models continue to latch on to lower snow amounts in the Mud Lake to
Idaho Falls area due to shadowing from the Central Mountains. While
we do agree there will be some shadowing, we did go ahead and
introduce some light QPF to these areas to keep snowfall in the
forecast where the NBM (heavily influenced by the hi-res, short-term
models) wanted to give almost no snow. Confidence in higher snow
totals increases the farther south you go. Around Pocatello, snow
totals will be closer to 2 to 3 inches. In the southern portion of
our area (Burley, Malta, Malad, Montpelier, etc) there is about a 50
to 80 percent chance of at least 6 inches of snow by Saturday
morning. In the Eastern Highlands, there is a 60 to 80 percent
chance of at least 6 inches of snow from McCammon to Montpelier and
about a 30 to 50 percent chance of 8 inches of snow from Lava Hot
Springs to Montpelier. Farther north from Driggs to Island Park
there is about a 40 to 60 percent chance of at least 3 inches of
snow. In the Central Mountains, there is about a 60 to 80 percent
chance of at least 4 inches of snow from Hailey up to Stanley.

In addition to the snow, we continue to have high confidence in very
strong wind gusts beginning to pick up this evening, courtesy of a
strong 700 mb jet. By about midnight tonight, we are expecting wind
gusts to already be in the 45 to 50 mph range through the eastern
Magic Valley and lower Snake Plain. These wind gusts will make it up
into the Idaho Falls and Rexburg areas just a couple of hours later.
Wind gusts will be almost as strong up in the Central Mountains.
Around 5 am, some of the strongest winds will be occurring near
Burley, Oakley, and the 84/86 Interchange with gusts nearing 60 mph.
By Friday evening, wind gusts will slowly diminish, with the biggest
drop off happening north of Blackfoot and by Saturday morning winds
will be much lighter, closer to 15 to 20 mph.

Our winter products continue unchanged at this point with Blizzard
Warnings out for all of the eastern Magic Valley to the
Idaho/Wyoming state line and north from the Utah/Idaho state line to
Ashton. Winter Storm Warnings continue from Ketchum northward and
Winter Weather Advisories for the northern portion of our CWA. We
continue to remind the public that Blizzard Warning criteria is
sustained winds/frequent gusts of at least 35 mph and blowing snow
reducing visibility to a quarter mile or less for at least three
hours. AMM

.LONG TERM...Saturday through Thursday. Second significant storm in
series continues Saturday into Sunday for East Idaho. Winds
fortunately look to be significantly less, below thresholds of
concern, though a few areas may still be breezy especially early in
the day Saturday. Models have trended upwards again on QPF and snow
potential, with accumulations falling generally south of a line from
Stanley to Driggs, concentrated over the southern highlands.
Definitely potential to extend some type of headline into the
southern portions, but most likely either Winter Weather Advisory or
Winter Storm Warning for heavy snow, depending on elevation and
area. Arctic air mass spilling over the Divide continues with
northerly gap winds early in the day, resulting in dangerous wind
chills below -20F. Wind chill watch remains in effect. Remnants of
Saturday snows continues across southeast corner of forecast area
into Sunday, with models now suggesting spillover northwest into
the Pocatello region. This is a jump over previous forecasts, so
further fluctuations are expected as the models hone in on the
timing. Very cold temperatures continue Sunday into Monday,
especially across northern stretches of the Snake Plain/Island
Park area. NBM deterministic had a significant jump in
temperatures Sunday night into Monday, so blended with previous
forecast and 50th percentile NBM. This preserved the temperature
trend Sunday - Tuesday. Could see Wind Chill concerns spilling
over at least until Monday morning. Weak ridge Tuesday short-lived
as both GFS and ECMWF deterministic runs spill energy out of
Canada into Montana/Idaho for the Wednesday and Thursday time
frame. Stayed with the NBM through this time period, with light
snow potential for most areas. DMH

&&

.AVIATION...Major area-wide impacts are anticipated for this TAF period due to
the combination of strong winds and snow, leading to BLSN and
reductions in VIS. Wind gusts will increase beginning this afternoon
as snow showers increase across the region. Confidence is high in
west winds remaining at least 30 to 40 kts across much of the region
Friday, with even stronger gusts around 40 to 50 kts or more
overnight Thursday night through early Friday afternoon.
Anticipating MVFR/IFR conditions at all terminals to persist
throughout Friday. Brief periods of LIFR VIS will be possible during
the period of strongest winds during the overnight hours through
Friday afternoon. Snow will continue throughout the weekend,
generally south of the Snake Plain, but winds will dramatically drop
off by early Saturday. Cropp

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Blizzard Warning until 5 AM MST Saturday for IDZ051-054>063-075.

Blizzard Warning until 5 PM MST Friday for IDZ052-053-064-065.

Wind Chill Watch from Friday evening through Saturday morning
for IDZ052-053-064>067.

Winter Weather Advisory until 5 PM MST Friday for IDZ066>070.

Winter Storm Warning until 5 AM MST Saturday for IDZ071>074.

&&