Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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385
FXUS65 KSLC 051145
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
445 AM MST Mon Dec 5 2016

.SYNOPSIS...A cold front will cross northern Utah this morning
before stalling across central Utah this afternoon. A second,
colder storm system will bring snow and the coldest temperatures
of the season to most of Utah and southwest wyoming for midweek.

&&

.SHORT TERM (Through 12Z Thursday)...A broad cyclonic flow
encompasses much of the northern and central U.S. this morning,
anchored around an upper low spinning over northern Saskatchewan.
A pair of shortwave features rotating through this flow will bring
much colder air and a chance of snow to the forecast area through
midweek.

The first of these waves is currently rotating through the
northern Rockies, with the associated surface front currently
crossing northern Utah. This front has pushed south of the upper
cold pool, which remains across northern Idaho/western Montana,
and as such profiles overtop of the surging low level baroclinic
zone are fairly stable, which will significantly limit
precipitation this morning along the Wasatch Front and adjacent
terrain. Nonetheless radar has shown an increase in precipitation
along the advancing baroclinic zone, and as such will likely see a
period of light snow across areas south of I-80 across Salt Lake
and Utah Counties this morning with little if any valley
accumulation. As the aforementioned shortwave continues east, the
surface boundary is expected to stall across central Utah this
afternoon with little if any lingering precipitation.

A break in precipitation is expected tonight, before the next
upstream wave currently along the British Columbia coastline digs
into the Great Basin during the day Tuesday. The models have been
trending slower with this wave, and as such have lowered POPs
later tonight into Tuesday morning across most areas, however did
retain chance POPs across northern Utah north of I-80 Tuesday
morning where warm advection may bring a period of light snow.
This second wave is forecast to cross northern Utah Tuesday
afternoon and evening bringing a period of light snow to northern
and central Utah with modest accumulation at best.

The more noteworthy aspect of this second wave will be the much
colder airmass which follows. 700mb temperatures Wednesday morning
are forecast around -18C Wednesday morning, which will keep max
temperatures Wednesday in the low to mid 20s across most northern
and central valleys, and single digits in the mountains.

.LONG TERM (After 12Z Thursday)...Flow aloft is progged to shift
to westerly by Thursday morning as a warm front moves through,
advecting a moist airmass back into the forecast area. This will
allow precip to redevelop over northern Utah, persisting through
Friday before temperature advection becomes more neutral. Maxes
are expected to run at least a few degrees above climo by Friday
afternoon with the warmer airmass and enough flow to erode any
inversions.

Global models then indicate a cooling trend for northern Utah and
southwest Wyoming with a cold front settling in during the day
Saturday as a weak wave grazes the forecast area. A good jet over
Idaho should keep a bit of instability around for a few showers.
EC/GFS then keep a somewhat active pattern going through day seven
with another weak wave moving through in zonal flow. Because the
models continue to disagree quite a bit with regard to the timing
and strength of this next wave, have opted to keep POPs near climo
for days six and seven.

&&

.AVIATION...VFR conditions are expected to prevail at the SLC
terminal through the morning. Showers have developed in the vicinity
of the terminal and will continue through about mid-morning before
weakening. Cigs at or below 6000 ft AGL should prevail after 12Z,
with a 40 percent chance of low-end MVFR to high-end IFR conditions
developing at times in snow showers. Cigs are expected to improve
between 15Z and 17Z. Northwest winds are expected throughout the
day.


&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...None.
WY...None.
&&

$$

Seaman/Traphagan

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