Winter Storm Warning 16, 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, Tooele County, UT, Utah County, UT, Wasatch County, UT, Washington County, UT, Wayne County, UT, Weber County, UT, Uinta County, WY

Area Forecast Discussion
National Weather Service Salt Lake City UT
512 AM MDT Sat Apr 1 2023

.SYNOPSIS...Warmer and dry conditions will last through Saturday.
A winter storm that will start early in the week will come with
gusty winds, rain, and snow.

&&

.DISCUSSION...A dry and relatively mild zonal flow has overspread
much of the Great Basin early this morning, downstream from a
shortwave trough making landfall along the Pacific Northwest
coast. As this wave moves inland today, low level southwesterly
flow will strengthen across the forecast area and result in
locally breezy conditions across the western valleys. This will
also aid in mixing this afternoon, allowing temperatures to reach
the upper 50s to potentially low 60s along the Wasatch Front, with
similar max temps across central/southern valleys as well.

The aforementioned shortwave trough will brush by northern Utah this
evening, pushing a shallow boundary southward into the forecast
area. Moisture accompanying the trailing low level baroclinic zone
will bring showers mainly north of I-80. Initially snow levels will
remain well above the valley floors, but will fall to the valley
floors after midnight across the Cache and northern Box Elder
Counties, resulting in a changeover to snow for these areas. Little
if any accumulation is expected through 12Z Sunday.

A broad longwave trough will be pushing inland from the PacNW
Sunday. Southwest Wyoming and Utah will be in zonal flow, closer
to shortwave energy to the north. Scattered showers, with valley
rain and snow and mountain snow are expected with that, primarily
for far northern Utah.

The low will dig southward into Monday near the Pacific coast. A
strong baroclinic zone will have entered northern Utah by Monday
morning. Upper diffluence east of the longwave trough and the
baroclinic zone will bring sufficient forcing for better
precipitation chances by Monday morning. Winds will transition to
northwest with cold air advection dropping snow levels below
valley floors throughout northern Utah. With that, Monday travel
impacts are nearly guaranteed in the higher elevations of northern
Utah, while valleys will mostly have transitioned to snow by the
morning commute. Snow rates will peak for most places during the
day on Monday as the baroclinc zone tracks from northwest to
southeast while transitioning from more of a west to east
orientation to a southwest to northeast orientation. With good
agreement from various guidance on snow accumulation meeting and
exceeding criteria, expanded the Winter Storm Watch to include
most Utah valleys, including those in the interstate corridor into
southwest Wyoming and throughout Utah.

Ensembles are in good agreement of the low strengthening, with
cyclogenesis taking place and a pivoting of the baroclinic zone.
There's uncertainty where precisely, but that would bring enhanced
synoptic lift and locally higher snow accumulations Monday.

Further south, a very good setup for gusty southwest winds will be
in place. All guidance points at winds meeting headline criteria
for portions of eastern and southeastern Utah. A High Wind Watch
was issued for that, with peak gusts Monday afternoon in that
portion of the state likely to exceed 65 mph.

The low will push into Utah Monday into Tuesday. The strongest
synoptic forcing will have exited by that point, with snow chances
tapering off in southern Utah. Snow will continue for much of
northern Utah, as strong lapse rates in a moist northwest flow
will last through the day. Confidence in snow accumulations is
lower, as various vorticity maxima and shortwaves will be more of
a factor, but locations that often receive enhanced snow in
northwest flow will likely receive the most accumulation.

Either record or near record cold temperatures are forecast
throughout southwest Wyoming and Utah Tuesday. Forecast high
temperatures slightly above freezing are 20-30 cooler than normal
for this point.

Remnant snow showers will last into Wednesday, as cyclonic flow
and more moist upslope flow will keep snow going in the northern
mountains. Precipitation is expected taper off into Wednesday.
Forecast confidence is much lower later in the week, as ensembles
have a lot of disagreement.

&&

.AVIATION...KSLC...VFR conditions with south winds will prevail
through this evening. Wind gusts may exceed 25 kts (45% chance)
between 16Z today and 02Z this evening.

.REST OF UTAH AND SOUTHWEST WYOMING...VFR conditions will
prevail at all TAF sites through this evening. Gusty south to
southwest winds can be expected this afternoon and early evening. A
weak cold front may bring periods of MVFR to IFR conditions along
the Idaho border late this evening into tonight.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Winter Storm Watch from late Sunday night through Tuesday
     afternoon for UTZ101>109.

     Winter Storm Watch from Sunday afternoon through Tuesday
     afternoon for UTZ110>112.

     Winter Storm Watch from Monday morning through Tuesday afternoon
     for UTZ113-115>118.

     High Wind Watch from Monday morning through Monday evening for
     UTZ121-128-130-131.

     Winter Storm Watch from Monday afternoon through late Monday
     night for UTZ122-125.

WY...Winter Storm Watch from late Sunday night through Tuesday
     afternoon for WYZ021.

&&

Wilson/Seaman

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