Snow Squall Warning 3, NWS Pocatello, ID

Area Forecast Discussion
National Weather Service Pocatello ID
150 PM MST Thu Mar 9 2023

.SHORT TERM...Tonight through Friday night. A low pressure system
centered off the NW coast early this afternoon will direct a strong
inland penetrating Atmospheric River into SE Idaho tonight through
Friday. The low off the NW coast will advance east along the
Canadian border Friday afternoon and night with an associated cold
front pushing from west to east across the region during the
afternoon and evening hours sweeping much of the Atmospheric River
moisture south and east of the region by Saturday morning. Ahead of
this frontal boundary we will see heavy snowfall across most of the
SE Idaho mountains and the front range and upslope valley locations
leading into the CNTRL mountains from Richfield to Howe. Further
south, we will see very strong downslope winds across the southern
highlands and along the Interstate corridor from Pocatello to
Burley. Wind gusts exiting from the southern mountain valleys will
likely reach 60 mph in a number of locations. To complicate matters,
warming temperatures and rising snow levels ahead of the cold front
Friday afternoon will encourage the development of rain in the Snake
River Plain as far north as Ashton. Thankfully the heaviest
precipitation in the Snake River Plain will likely accompany the
front along with colder temperatures late Friday afternoon with rain
changing over to snow fairly rapidly. And finally, there does appear
to be some instability associated with the frontal passage Friday
afternoon up along the Montana border where we may see some brief
but intense convective bands moving through the upper Upper Snake
River Plain and Highlands. By Saturday morning, the storm will have
passed east of the region with NW flow aloft encouraging light
snowfall activity in the upslope regions of the CNTRL and ERN
mountains. Huston

.LONG TERM...Saturday through next Thursday.
Saturday and most of Sunday will be a quiet weather period before
our next system arrives. Only slight chances for light mountain snow
will continue Saturday and Sunday as models feature a weak transient
ridge building in through Monday. Meanwhile, a series of lows will
rotate along the coast of Washington, with an associated trough
moving inland late Monday/Tuesday morning. This combination of
features and synoptic setup will result in favorable flow for the
advection of moisture into the region, marking our next atmospheric
river event, which will occur Monday through Wednesday. A prolonged
period of southerly flow across our southern zones will result in a
warming trend throughout much of the extended period. Daily highs in
the low to mid-40s will mean rain or rain/snow mix as far north as
the upper Snake Plain Monday and Tuesday. GEFS is currently running
a bit higher than EPS with regard to mean 24-hour snow totals for
the Monday through Tuesday evening timeframe, with a mean of 4"-10"
across the central Idaho mountains and valleys and 2"-6" for the
eastern and southeast highlands. For this same period, The National
Blend is indicating a 30-80% probability of 8 or more inches for
much of the central mountains and up to a 60% probability of 4 or
more inches across the Centennials, Big Holes and Bear River Range.
The NBM only shows around a 40% chance that the southern highlands
will see 2". The potential for flooding will persist considering
additional rainfall and snowmelt following the event on Friday. Come
Thursday, high pressure will begin to build in again as snow showers
exit to the northeast. Cropp
&&

.AVIATION...Precipitation will overspread the region from west to
east, beginning around 4z tonight.  Hi-res models show the heaviest
precipitation moving through 5z-12z, with another potent round after
15z tomorrow.  All sites will see snow at the onset, with
precipitation switching over to rain by late morning to early
afternoon at KBYI, KPIH, and KIDA. Winds will begin to increase this
evening and peak during the afternoon tomorrow, with S/SE winds over
20 kts and gusts exceeding 40 kts. Expect reductions in VIS to IFR
due to snow and even blowing snow at times, with the blowing risk
especially high at KDIJ. Cropp
&&

.HYDROLOGY...
Atmospheric river moisture and strong southerly flow will bring
afternoon highs Friday to near 50 in the Burley area and low- to mid-
40s across the Snake River Plain. Warmer temperatures coupled with
rain and strong winds may lead to an increased potential for snow-
melt flooding across lower elevations. Early indications suggest the
most likely area for snow-melt flooding would be south of Burley
through Oakley. If you live along the Interstate 84/86 corridor,
you may want to exercise extra precautions now and move heavy snow
accumulations away from the foundation of your home and ensure storm
drains are cleared. MacKay/Huston
&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning from 9 PM this evening to 5 AM MST Saturday for
IDZ051-052-068-069-071>075.

Winter Weather Advisory from midnight tonight to 9 PM MST Friday for
IDZ053-065-070.

High Wind Warning from midnight tonight to 9 PM MST Friday for
IDZ054>057.

Winter Storm Warning from midnight tonight to 5 AM MST Saturday for
IDZ058-060-062>064-066-067.

Winter Weather Advisory from midnight tonight to 5 AM MST Saturday
for IDZ059-061.
&&