Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 302307

Area Forecast Discussion
National Weather Service Salt Lake City UT
507 PM MDT Thu Mar 30 2017

.SYNOPSIS...An upper low will slowly drift east along the Utah
Arizona border tonight through Friday. High pressure will return
Saturday, followed by another cold front early next week.


.SHORT TERM (THROUGH 00Z MONDAY)...The storm system has pinched off
into a closed low with a circulation center near the southern Sierra
Nevada. The cold front has crossed northwest Utah and is starting to
move into southwest Utah. Pressure rises across northeast through
central Nevada will keep a tight surface gradient and gusty winds
behind the front, but the 700mb boundary is already weakening across
northern Utah, so the front will make little if any additional
forward progress. The 700mb boundary remains stronger across
southern Nevada, but it too will weaken as it enters Utah.
Otherwise, prefrontal winds will continue across southern Utah
through this evening.

An area of showers with embedded thunderstorms and locally heavy
precipitation is associated with the boundary, while prefrontal
precipitation has become a bit more widespread over central and
eastern Utah. With the low center then tracking across southern Utah
tonight into tomorrow, moisture wrapping around the low will favor
precipitation across southern and portions of eastern Utah as well
as southwest Wyoming, but in particular the I-15 corridor across
southwest Utah and adjacent mountains, as well as the north slopes
of the Uintas. The coldest air will be near the low center across
southern Utah, and looks to fall to the 5000-5500ft range overnight.
Northern Utah will see higher snow levels as easterly flow will
result in warm advection tonight. This warmer air will spread into
west-central and southwest Utah a bit faster now as well, with snow
levels rising a bit tomorrow. As a result, some of the going winter
weather highlights now seem pretty marginal. This includes the
Wasatch Mountains and West-Central Utah zones. Have left those
highlights in place for now but with low-end amounts. In west-
central Utah, the lower valleys are not expected to see much if any
accumulation; the focus is on the I-15 corridor, particularly the
area near Kanosh. Given higher snow levels, do not see much snow or
impacts for the Sanpete and Sevier Valleys, so have cancelled the
Winter Weather Advisory for that zone.

Easterly flow across northern Utah is still expected to max out
tomorrow night into Saturday morning. The surface gradient is still
not expected to be especially tight even with the 18z runs. Winds at
700mb are still forecast to reach 50kt across northeast Utah and
southwest Wyoming, but with modest cold advection. Expect gusty
winds near canyons, but still not confident enough to go with any
wind highlights at this time.

.LONG TERM (After 00Z Monday)...After the pleasant weekend, the next
shortwave trough drops in from the northwest on Sunday night and
Monday. There are still some model discrepancies about the structure
of this system and how far south it dives, but in general this looks
like a decently cold system, with 700mb temperatures dropping to -8C
to -10C across northern Utah by 18Z Monday. Because of this, have
made sure to at least have a mention of snow in the northern valleys
during the day Monday. Have also cooled temperatures and increased
POPs a bit across northern Utah through this period.

The trough will likely exit Monday night or Tuesday, though
significant warming is not expected until Wednesday as a high
amplitude ridge builds over the Great Basin. This should lead to
well above average temperatures Wednesday through Friday.


.AVIATION...Winds at the SLC terminal are expected to increase from
the north-northwest between 23Z and 02Z, with a 20 percent chance of
wind gusts greater than 30 mph. Continued shower activity across
northern Utah could produce erratic winds at times, and will likely
help keep ceilings below 7000 feet through at least 06Z. There is
also a 20 percent chance of MVFR conditions under the heaviest
showers between 00Z and 05Z.


UT...Wind Advisory until 9 PM MDT this evening for UTZ019>021.

     Winter Storm Warning until 6 AM MDT Saturday for UTZ009-015-016-

     Winter Weather Advisory until 6 AM MDT Saturday for UTZ007-008-

     Wind Advisory until 4 AM MDT Friday for UTZ005.

WY...Winter Weather Advisory from 3 AM Friday to 6 AM MDT Saturday
     for WYZ021.




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