Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 222153

Area Forecast Discussion
National Weather Service Salt Lake City UT
353 PM MDT Thu Mar 22 2018

.SYNOPSIS...Mild and moist southwesterly flow will remain across
much of Utah through this evening, before a cold front crosses
the area overnight into Friday morning. A second cold upper level
trough off the Pacific Northwest coast will move east and impact
mainly northern and western Utah and southwest Wyoming this


.SHORT TERM (Through 12Z Sunday)...Strong and mild southwesterly
flow remains in place across the Interior West this afternoon, as
an upstream shortwave trough makes landfall along the California
coast. The remnants of an embedded Atmospheric River (AR) within
this flow continue to slowly spread eastward across the southern
Great Basin into southwest Utah. Increasing thermal/moisture
advection coupled with orographic forcing continues to allow for
areas of rain and high elevation snow (above 9500 feet) across
both northern and southwest Utah. This will continue to increase
through the evening hours as the upstream shortwave trough
approaches the area, and have maintained high PoPs as a result.

Southerly surface winds have also been increasing over the past
couple of hours as the pressure gradient tightens in response to
pressure falls across far northwest Utah with gusts into the 50
mph range. As such have maintained the going High Wind Warning
through mid evening, although winds may be slow to diminish until
a cold front passes overnight.

The cold front associated with the approaching shortwave is
forecast to push into northern Utah after midnight serving as a
focus for heavy precipitation, and lowering the snow levels below
7000 feet. This front will quickly sweep out of the area Friday
morning allowing for a quick drying trend by afternoon. Anticipate
a band of very heavy snow with this front across the higher
terrain which will likely impact travel, and have issued a Winter
Weather Advisory for the Wasatch Range through Friday morning.

A brief dry period is expected Friday afternoon through Friday
night, before an ejecting shortwave passing to the northwest
pushes a shallow cold front into northern Utah. This will serve
as a focus for showers Saturday afternoon through Saturday

.LONG TERM (After 12Z Sunday)...The longwave Pacific trough will
move eastward during the day on Sunday splitting as it does so.
This feature will push a cold front through the state on Sunday
resulting in a chance of valley snow for most of the state. There
is still a good amount of uncertainty regarding when/where the
strongest precipitation will set up in association with the
baroclinic zone. Right now the region/timing of best dynamics
(height falls/upper divergence) and frontogenetic forcing looks to
be Sunday afternoon along a SW-NE oriented line extending from
just north of Cedar City to Utah county. It is challenging to
gauge potential travel impacts along the northern urban corridor
given the apparent southern focus of heavier precipitation and the
fact that the precipitation would likely occur during daylight
hours limiting road accumulations. However, the I-15/70 corridor
in central and southern Utah could be a potential trouble spot
Sunday evening if this setup holds.

The splitting cold core low moves over the area early Monday
morning with guidance currently depicting another round of snow
forming over northern Utah as it moves overhead. There are still
discrepancies among guidance over where this split occurs and
consequently how much energy is associated with the system as it
passes through Utah. The EC/CMC depicts the northern split as
fairly progressive/low amplitude with light snowfall in northern
Utah valleys Monday AM, and only light precipitation lingering in
the mountains later Monday. The 12Z GFS depicts the northern vort
lobe as fairly robust (initially) and generates fairly healthy
snowfall for northern Utah valleys Monday AM, with consistent
moderate snowfall in northerly- flow favored orographic areas
throughout the day.

Guidance then comes into better agreement that the southern split
will dominate and slowly move to the southeast of the forecast
area Tuesday-Wednesday. This setup could result in some gusty
canyon winds in SW Utah Monday night into Tuesday morning but
details are still highly dependent upon the track of the low and
the sfc.gradient/temperature advection pattern that develops in
response. Finally ensemble guidance does depict a bit of a pattern
change with ridging generally developing just off the west coast
Tuesday onward. Although this synoptic pattern would favor drier
conditions than what we have experienced thus far in March there
would still be the potential for glancing blow from systems
rounding the ridge crest particularly in northern and eastern


.AVIATION...Gusty winds will continue to increase at the SLC
terminal into the evening. A cold front is expected to cross the
terminal between 07-08Z, shifting winds to the northwest. Winds
may return to the southeast by 12Z. Moderate to heavy rain is
expected with this front, which will likely bring periodic MVFR
conditions to the terminal between 07-14Z.


UT...High Wind Warning until 9 PM MDT this evening for UTZ003-005-015-

     Winter Weather Advisory until noon MDT Friday for UTZ007-008.




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