Winter Storm and Heavy Snow in Idaho, April 10 to 13, 2022

Area Forecast Discussion
National Weather Service Pocatello ID
258 AM MDT Sun Apr 10 2022

.SHORT TERM...Today and Monday. A lingering area of snow will
persist earlier on this morning along and east of I-15 across
portions of the eastern and southeast highlands. This band
potentially will extend back toward Arco and INL briefly around
sunrise. Across the Snake Plain where this band exists, look for
little accumulation especially on warmer surfaces. Across the
higher elevations, look for anywhere from a Trace to maybe a
couple of inches additional snowfall at mid and upper slopes. As
we head into this afternoon, look for additional showers to form
as the next push comes across central and eastern Idaho. This
should last into the evening hours, with a rapid drop off after
sunset. We are even expecting a couple of thunderstorms up around
Island Park during the late afternoon/early evening timeframe.
Most locations will see light precipitation, although heavier
showers/storms could easily produce a quick burst of snow or
graupel around 1". Winds will also pick back up today and this
evening. We are confident that Lake Wind conditions will occur
on American Falls Reservoir. We are NOT confident that we would
reach Wind Advisory thresholds across the Snake Plain and Magic
Valley. We left wind speeds hovering just below those levels, but
certainly some thing to keep an eye on. It is possible that we
could see rather gusty winds with showers or storms that develop
instead of widespread stronger winds.

Toward sunrise tomorrow and throughout the day, a mix of rain and
snow develops ahead of a cold front. It looks like a decent area
of upslope precipitation (mostly snow) forms around the Shoshone
Lava Beds to near Arco, and into the central mountains. This looks
like a good snow event for the Wood River Valley and surrounding
mountains with southerly flow setting up. As we get into the
afternoon, showers and thunderstorms will increase areawide...with
a decent band of showers and storms developing as the cold front
sweeps through the area. As the cold front exits tomorrow night,
the bulk of the moisture will fall across the central mountains,
eastern and southeast highlands. It will be breezy at times, so
limited blowing snow is possible. We also would be surprised if we
see snow squall conditions with the front, with strong winds
remaining across the Snake Plain, Magic Valley and South Hills. At
this point, we will let day shift handle any Winter Weather
Headlines for Monday and Monday night...but it does appear we will
need something for at least the Wood River Valley and surrounding
mountains and potentially other higher elevations.  Keyes

.LONG TERM...Tuesday through next Sunday.
The extended period is one of unsettled weather.  The upper-level
trough over the western U.S. continues to shift eastward Tuesday,
with a secondary low approaching the PNW.  A series of shortwaves
will move through southern ID throughout the week as multiple upper
troughs move in from the west.  Winds will continue to be elevated
Tuesday and Wednesday, with strong west/northwesterly winds over
southern ID. Extreme Forecast Index (EFI) has SE Idaho, especially
portions of the Magic Valley, highlighted for strong winds on
Wednesday.  Have started to nudge winds up slightly by blending with
NBM 90th Percentile.  There is also the potential for the SE
Highlands to see thunderstorms both Tuesday and Wednesday afternoon
ahead of these shortwave troughs. Snow levels Tuesday will allow for
snow as the sole precip type region-wide through Thursday morning,
after which we could see rain start to mix in across the Snake River
Plain and Magic Valley each afternoon through the end of the
extended. Temperatures will remain well below climatological norms,
with highs in the teens-30s Tuesday through Wednesday and widespread
lows in the single digits to 20s. Temperatures will start to
increase a bit Thursday forward, with max temps in the 20-50 degree
range and lows just shy of reaching above freezing across the Snake
Plain and Magic Valley.  24 hr. snow totals for Tuesday AM-Wednesday
AM look to be 2-7 inches for the Central Mtns. and south of I-15
between Pocatello and Idaho Falls, with slightly higher totals along
the highest peaks, and 2-6 inches across the E/SE Highlands and Bear
River Range. Precipitation Wednesday and beyond will be a bit more
showery and additional accumulations will be very light. Currently
expecting up to an inch of additional snowfall for our mountainous
regions and even less for lower elevations Wednesday-Thursday.  The
Bear River Range could see a few additional inches.  By Saturday
there is greater variance among ensemble cluster solutions with
greatest discrepancy relating to the timing of features.  A third
low pressure system reaches the coast late Friday, but ECMWF is a
bit slower than GFS with the progression of the trough and
subsequent ridging building in along the coast later Saturday.
Either way, it won't be until Sunday that we should start to see
skies clearing under high pressure, albeit brief as the next closed
low heads for the PNW. Cropp

&&

.AVIATION...VFR conditions forecast at all terminals, with potential for
intermittent reductions in VIS due to blowing snow/dust.  Winds will
be elevated again today, peaking by early evening and subsiding late
tonight. Sustained winds in the 20kt range and 30kt+ gusts forecast
at KPIH and KIDA, with a bit lighter winds expected at KBYI.
Winds will be even calmer at KSUN and KDIJ, with sustained winds
likely under 15kts and less potential for gusts.  KDIJ will see the
most impacts, with snow and slight chance for thunderstorms nearby.
Have kept VCSH at KIDA and KSUN.  Precip will exit the region by
late tonight. Cropp

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Lake Wind Advisory from 9 AM this morning to 9 PM MDT this
evening for IDZ054.

&&

Special Weather Statement
National Weather Service Pocatello ID
423 AM MDT Sun Apr 10 2022

IDZ052>054-058-062>064-101315-
Arco/Mud Lake Desert-Big Hole Mountains-Upper Snake River Plain-Marsh
and Arbon Highlands-Caribou Range-Blackfoot Mountains-Lower Snake
River Plain-
423 AM MDT Sun Apr 10 2022

...AN AREA OF MODERATE SNOW WILL PRODUCE SLICK ROADS THIS MORNING...

At 417 AM MDT, an area of moderate snow extended from the INL
through Blackfoot, Idaho Falls and into the southeast highlands.
Accumulations around one inch per hour are creating slick roads
this morning.

Locations impacted include...
Idaho Falls, Blackfoot, Swan Valley, Blackfoot Reservoir, Wayan,
Palisades Reservoir, Chesterfield Reservoir, Ammon, Shelley, Iona,
Firth, Irwin, Rose, Pingree, Henry, Fort Hall Putnam Lodge, Fort
Hall Eagle Lodge and Fort Hall Lincoln Creek Lodge.

Conditions can deteriorate rapidly in winter weather situations. Be
prepared for snow or ice covered roads. Slow down and allow extra
time when traveling.

LAT...LON 4314 11290 4364 11233 4345 11105 4254 11105
TIME...MOT...LOC 1017Z 290DEG 33KT 4323 11219

Keyes