Heavy Snow in Utah, January 22 to 24, 2021

Area Forecast Discussion
National Weather Service Salt Lake City UT
1050 AM MST Fri Jan 22 2021

.SYNOPSIS...A slow moving weather system will cross the
Intermountain region late today through Saturday. Another storm
system will affect mainly southern Utah Monday through Tuesday.

&&

.DISCUSSION...Morning water vapor imagery and objective analysis
show an upper low spinning over northern CA with a secondary
shortwave on its heels digging off the Pacific Northwest coast.
Downstream southwesterly flow has overspread the Great Basin in
the wake of a mid level shortwave ridge axis located along the
UT/CO border. At the surface shallow cold pools remain in place at
the bottom of several northern valleys including near the Great
Salt Lake basin near and just west of the northern Wasatch Front,
as well as the Cache Valley and western Uinta Basin.

As the northern CA low rotates further inland across the Great
Basin today, strengthening warm air/moisture advection within a
southwesterly flow will increase across the forecast area
allowing precipitation to develop, mainly impacting areas favored
within this flow regime such as areas near Brian Head, Provo
Canyon, etc... 700mb temps warm into the -6C to -4C range which
combined with mixed valleys should keep snow levels above the
valley floor through this evening except perhaps in a couple
stubborn areas such as the Cache and western Uinta Basin, as well
as possibly Castle Country near Price.

The upper low is forecast to eject across the area overnight
through early Saturday bringing fairly widespread precipitation
to much of the area roughly along and south of I-80 with snow
levels falling to the valley floors late tonight. With the
trajectory of the ejecting wave southwesterly flow will prevail
across most of central and southern Utah again favoring areas
which do well within this flow regime.

As the wave continues northeast a deformation axis is expected to
set up across northern Utah/southwest Wyoming late tonight through
much of the day Saturday. This band appears most likely to set up
across the northern Wasatch Front eastward into the Cache and Bear
River valleys, keeping any appreciable snowfall north of I-80 for
much of Saturday.

Current forecast has Winter Weather Advisories across the higher
terrain which looks good. Will likely need to expand into some
valleys with the afternoon package, most likely areas north of
I-80 for late tonight through Saturday.

&&

.AVIATION...VFR conditions are expected at the SLC terminal through
the daytime hours. Cigs are expected to lower to or below 6000 feet
AGL between 22Z and 02Z due to precipitation in the vicinity of the
terminal. Light winds are expected to increase out of the south by
the early afternoon.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Winter Weather Advisory until 8 PM MST Saturday for UTZ007>010.

     Winter Weather Advisory until noon MST Saturday for UTZ517-518.

WY...None.
&&

Seaman/Traphagan

For more information from NOAA's National Weather Service visit...
http://weather.gov/saltlakecity

For frequently asked questions about the Area Forecast Discussion
visit...
http://weather.gov/saltlakecity/general/afd_faqs.php

Hazardous Weather Outlook
National Weather Service Salt Lake City UT
617 AM MST Fri Jan 22 2021

UTZ001>016-019>021-517-518-WYZ021-231400-
Cache Valley/Utah Portion-Northern Wasatch Front-
Salt Lake and Tooele Valleys-Southern Wasatch Front-
Great Salt Lake Desert and Mountains-Wasatch Mountain Valleys-
Wasatch Mountains I-80 North-Wasatch Mountains South of I-80-
Western Uinta Mountains-Wasatch Plateau/Book Cliffs-
Western Uinta Basin-Castle Country-San Rafael Swell-
Sanpete/Sevier Valleys-West Central Utah-Southwest Utah-
Utahs Dixie and Zion National Park-South Central Utah-
Glen Canyon Recreation Area/Lake Powell-Central Mountains-
Southern Mountains-Southwest Wyoming-
617 AM MST Fri Jan 22 2021

This Hazardous Weather Outlook is for the western two thirds of
Utah and southwest Wyoming.

.DAY ONE...Today and Tonight

Precipitation will develop today and increase in coverage and
intensity tonight as a storm system moves into the area.
Significant snow is expected in the mountains while many valleys
will initially see rain or a rain/snow mix gradually transition to
snow late tonight.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

Precipitation will continue across mainly northern and central
Utah Saturday through Saturday evening, with accumulating snow
expected down to the valley floors. Snow will be heavy at times
in the mountains.

Another winter storm is expected to cross the area Monday through
Tuesday. Widespread accumulating snow will be possible across
mainly southern and central Utah, with a potential for significant
snow in the southern mountains.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed. Please relay any information
about observed severe weather to the NWS while following all
local, state, and CDC guidelines.

For more information from NOAA/s National Weather Service visit...
http://weather.gov/saltlakecity

For information on potential road travel impacts visit...
http://www.udottraffic.utah.gov/roadweatherforecast.aspx