Winter Storm Warning 17, NWS Salt Lake City, UT

Beaver County, UT, Box Elder County, UT, Cache County, UT, Carbon County, UT, Davis County, UT, Duchesne County, UT, Emery County, UT, Garfield County, UT, Iron County, UT, Juab County, UT, Kane County, UT, Millard County, UT, Morgan County, UT, Piute County, UT, Rich County, UT, Salt Lake County, UT, Sanpete County, UT, Sevier County, UT, Summit County, UT, Utah County, UT, Wasatch County, UT, Washington County, UT, Wayne County, UT, Weber County, UT

Area Forecast Discussion
National Weather Service Salt Lake City UT
431 AM MST Sat Nov 18 2023

.SYNOPSIS...A change in the weather pattern is forecast for the
weekend as two waves of energy track through the region. Sundays
weather system will be the more impactful of the two waves with
heavy mountain snow accumulations expected.

&&

.SHORT TERM (Until 12Z/5AM Monday)...A shortwave is expected to
move through the area during the day on Saturday. The main
precipitation associated with this wave will be a band of valley
rain and mountain snow that will mainly impact southern and
eastern Utah. Scattered showers are expected in northern Utah and
over to the Uinta Basin. Snow levels will stay between 7500ft and
8000ft. Not much is expected in the way of precipitation totals as
up to 0.25" of rain could be possible. Higher elevation areas may
see up to a few inches of snow. Thunder can not be ruled out
during the afternoon and into the evening hours.

As this wave exits, the more potent storm begins to move into
northern Utah by early Sunday morning as a trough will move down
into the Great Basin region. There is still some uncertainty as
to the exact track the trough takes and how far it digs. The exact
trajectory of this trough will be something to watch as this would
influence total snowfall and snow levels across Utah and southwest
Wyoming. If this trough moves more directly through the area, then
the coldest air will follow it and allow snow levels to drop even
more and snowfall to be higher in the areas that are favored in
northwest flow. Current forecasts have the trough moving through
eastern Nevada/western Utah. With this trajectory, 700mb winds
would mainly be northerly and not necessarily aid in adding more
snowfall in the northwesterly favored flow areas. There will be an
area of higher precipitation rates along and ahead of the
baroclinic zone, so higher elevation areas could stack up on snow
relatively quickly. With all this being said, the most significant
snowfall will be for areas above 7000ft with totals between 10
inches and 14 inches for much of the central and northern
mountains. Snow levels will drop throughout the day and be around
5000ft by Sunday evening so there is some possibility in lower
valley snow occurring, especially on the benches.

This weather system will also bring gusty winds with it. Strong
northwesterly winds will be possible in northwestern Utah Sunday,
areas like SR-30 and I-80. These strong winds could also be
problem for areas in east central Utah like Castle Country. With
these northwest winds, downsloping will help to increase the winds
even more. A wind product may be needed for Castle Country along
SR-10.

.LONG TERM (After 12Z/5AM Monday)...Mid level ridging will bring a
drying and gradual warming trend across the forecast area through
midweek. Initially a cool and stable northerly flow will reside
across the forecast area Monday, as the weekend trough slowly pulls
away from the region. A few of the slower solutions maintain a small
chance for showers lingering into the day Monday, otherwise
temperatures will run 5-8 degrees below climo Monday afternoon
across the forecast area, along with the potential for enhanced
gap/downslope winds persisting over portions of southern and east
central Utah. As this ridge becomes established across the region
Tuesday into Wednesday, temperatures will moderate considerably.
This warming trend will be most notable across higher elevations,
while the warming may be more muted across northern and western
valleys and dependent on how the weekend event ends up playing out,
as conditions could become favorable for valley inversions to
become established.  For now have maintained NBM temperatures
through midweek, but these may be on the high side for these
valleys.

Forecast uncertainly increases considerably for the latter portion
of the week, as a mid level trough digs into the western CONUS.
Model solutions vary between a brush-by system impacting mainly
northern Utah, and a more robust low developing across the Great
Basin Thursday through Friday, which would bring widespread travel
impacts for the Thanksgiving Holiday and beyond. Given this large
spread in potential solutions, have again leaned toward the NBM for
guidance, which primarily focuses chance PoPs over northern Utah, but
seems to downplay the potential into central and southern Utah.
Those with holiday travel plans should monitor the forecast closely
over the coming days, as hopefully model guidance begins to
consolidate on a common solution.

&&

.AVIATION...KSLC...Predominant VFR conditions are expected at KSLC
today and tonight. Southeast winds will switch to the northwest
between 17-18Z, with a 20% chance this wind shift is delayed until
20Z or later. Scattered showers will develop this afternoon and
evening. CIGS may fall below 7 kft with these showers, but should
remain in the VFR category.

.REST OF UTAH AND SOUTHWEST WYOMING...Patchy fog will result in LIFR
to VLIFR conditions across portions of northern Utah this morning.
This fog will lift by late morning yielding predominant VFR
conditions. Scattered showers this afternoon may result in brief
periods of MVFR to IFR conditions.

Precipitation spreading into far southern Utah will bring local MVFR
to IFR conditions this morning, with snow levels remaining around
8000 feet. Conditions will improve midday, with lingering valley
rain and mountain snow showers bringing local MVFR to IFR
conditions. &&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...High Wind Watch from Sunday morning through Sunday evening for
     UTZ101.

     Winter Storm Watch from this evening through Monday morning for
     UTZ110>113-117.

     Winter Storm Watch from late tonight through Monday morning for
     UTZ125.

WY...None.
&&

Cecava/Seaman

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