Area Forecast Discussion
Issued by NWS Pocatello, ID

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000
FXUS65 KPIH 281045
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
345 AM MST Wed Feb 28 2024

.SHORT TERM...Today through Friday Night.
Early morning satellite imagery shows a ~973 mb low in the Gulf
of Alaska which is expected to move southeast over the coming days
bringing widespread precipitation and strong winds to CNTRL and
ERN Idaho as an atmospheric river of moisture moves onshore. Ahead
of the arrival of this system, look for relatively quiet and
mostly dry conditions for today with highs in the 30s/40s and best
chances for snow showers in the CNTRL Mountains and ERN
Highlands. Winds will also be slightly breezy today with gusts to
around 25 to 40 mph.

A mix of rain and snow will overspread NW to SE overnight tonight
and throughout the day on Thursday as winds steadily ramp up by
Thursday afternoon as a cold front begins to work through the NRN
Rockies. 40 to 60 kt 700 mb will shift overhead Thursday afternoon
through much of the day on Friday leading to widespread wind
gusts between 40 to 60 mph with locally higher gusts in wind prone
areas. Temperatures ahead of the cold front will trend well above
normal across our lowest elevations with highs in the 40s to mid
50s with a gradual cooling trend then expected through the weekend
as colder and drier air begins to build in out of the NW. Winds
will overall lessen Friday night into Saturday as the strongest
700 mb jet shifts south into the Great Basin but lingering 30 to
40 kt 700 mb winds will lead to continued breezy winds with areas
of blowing and drifting snow expected throughout this period of
high winds.

When taking a look a look at precipitation totals with this
system, look for accumulations to begin in the CNTRL Mountains and
ERN Highlands initially before overspreading south as a cold
front tracks through the region. This is looking to be a 72-hour
period of wet weather with no clear breaks in our area so we will
be running with longer than usual product headlines. Increased
model uncertainty continues regarding resolving exactly where we
saw a mix of rain/snow or all snow with some models showing VERY
different amounts associated with when we transition to snow
behind the cold frontal boundary. Expect changes to amounts and
hazards over the coming days as this comes into focus.

WINTER STORM WATCHES have been expanded to include all of the
mountains south and east of the Snake Plain in addition to the
Lost River Valleys and Arco/Mud Lake Desert to account for a mix
of moderate to heavy snow and strong winds. WIND ADVISORIES have
also been issued for the Upper/Lower Snake Plain and
Challis/Pahsimeroi Valleys where initially, wind and rain will be
the primary weather hazard transitioning to the potential need
later on for some version of a winter weather product to account
for colder temperatures supporting a changeover to all snow on
the backside of the cold front. Stay tuned over the coming days as
we track the latest. MacKay

.LONG TERM...Saturday through next Wednesday.
Saturday morning through next Wednesday. The moist atmospheric
river system from the short term forecast will continue through
early Sunday. Saturday morning expect cooler temperatures with
more widespread snow down to all valley floors. Also, winds will
drop off Saturday but still be breezy with gust near 20 to 30 mph.
The most likely valleys snow amounts are 2 to 6 inches. Higher
snow amounts will be on the eastern benches of the Snake plain and
the northern portions of the Upper Snake plain, north of Rexburg.
The snow forecast has a lot of uncertainty tied to it for
Saturday. If temperatures drop just a few more degrees over the
current forecast, some models show the upper end for snow amounts
(or 90th percentile) of around 7 to 10 inches for the benches and
the northern portions of the Upper Snake plain. The winter weather
highlights, most likely a winter storm warning (it is a winter
storm watch now), for moderate to heavy snow will continue for all
mountain zones through late Saturday afternoon in the Central
mountains and Sunday morning for our eastern areas. Winter weather
advisories will likely be needed for most valley zones.

Sunday look for moist northwesterly flow aloft bringing continued
light to moderate snow for the western Central mountains and the
Island Park area. By Monday the flow aloft becomes more westerly
still impacting the western Central mountains. Models then show
moist southerly flow for Wednesday, which would bring continued
moderate to heavy snow to the southern Central mountains.

The forecast period will start Saturday 3 to 6 degrees below
normal before dropping 5 to 10 degrees below normal Sunday and
then warming up by Tuesday and Wednesday to around normal. Wyatt

&&

.AVIATION...For the 12Z TAFS through 12Z Thursday.
Expect breezy winds across the area tonight through tomorrow. The
flow aloft will change from a more breezy northwesterly flow to a
breezy westerly flow. Expect VFR conditions for all TAF sites
except KDIJ. Look for MVFR CIGS for KDIJ this morning with
lingering snow showers before becoming VFR as early as late
morning and possibly as late as early afternoon. Wyatt

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Winter Storm Watch from Thursday morning through Saturday
afternoon for IDZ052-068-069.

Wind Advisory from 11 AM Thursday to 5 PM MST Friday for IDZ053-
054-070.

Winter Storm Watch from Thursday afternoon through Saturday
evening for IDZ056>063.

Winter Storm Watch from Thursday morning through Saturday
evening for IDZ064>067.

Winter Storm Watch from late tonight through Saturday afternoon
for IDZ071>075.

&&

$$


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