Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 022230
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
330 PM MST Fri Dec 2 2016

.SYNOPSIS...A cold upper trough will exit the area tonight. High
pressure will move over the region tonight into Sunday. A colder
upper trough will slowly cross the area through the first half of
the upcoming week.

&&

.SHORT TERM (Through 00Z Tuesday)...The two weak troughs that
merged overnight are now splitting again, with one centered over
southwest Wyoming and another over northwest Mexico. Shortwave
energy between the two is over western Utah, coincident with an
area of clouds and perhaps a bit of light precip. The clouds have
been eroding this afternoon and will continue to do so overnight
as the trough continues to weaken and shift east, moving out of
the area by Saturday morning.

High pressure centered off the California coast will build east
into the area over the weekend. However, a bit of shortwave energy
moving over the ridge will push some moisture back into far
northern Utah by Saturday morning. This will be enough for some
cloud cover, but any associated precipitation will be limited. The
building ridge will bring a warming trend through the weekend,
pushing maxes Sunday to near seasonal normals over northern Utah
and a few degrees above those values over southern Utah.

The moisture over northern Utah is progged to sag southward a bit
during the day Sunday ahead of the next storm system. This system
will bring a good cold front with it, dropping 700mb temps from
the -4C to -6C range Sunday afternoon to the -14C to -16C range by
Monday afternoon. Though the system initially looks quite moist as
it moves over the Pacific Northwest, global models currently indicate
it will dry out quite a bit as it moves into Utah and southwest
Wyoming. Think there will still be a decent burst of precip with
the front over northern Utah overnight Sunday into Monday morning,
but despite very good dynamics provided by a potent upper level
jet, the lack of moisture could limit accumulations. Precipitation
with the front is expected to diminish significantly Monday
afternoon as the airmass associated with it continues to dry and
it outruns its upper level support. Have adjusted POP grids
downward a bit with the drier trend in the models. Overall,
though, it should be noted that model run- to- run consistency has
not been great and confidence in any solution is a bit lower than
usual.

&&

.LONG TERM (After 00Z Tuesday)...As the large cold front
continues to push farther south through Utah, cold air aloft will
settle in across the Great Basin. Global models have trended back
and forth, however they are consistent in the fact that we will see
-13C or colder air Tuesday through the better part of Thursday,
advertising as low as -19C.

A second wave rotates around the larger trough, bringing another
shot of snow through the north central portions of Utah on Tuesday,
however timing among model solutions is out of sync, with the ECMWF
6 - 12 hours behind the GFS. Kept a mostly broad brush PoP trend
going for Tuesday, and tapering off by Wednesday. The flow pattern
remains a west- northwesterly heading, and in hindsight if the
moisture becomes better realized a long duration mountain snow event
could be on tap.

The GFS is quicker at ejecting the wave to the East on Thursday,
while the EC sags back a bit. This could play out to some inverted
valleys with such cold air stuck in valley locations with ridging
building in from the West (albeit weak) by Friday. Surface
temperatures still look to be the coldest on Wednesday during the
day, with high temperatures around 10 - 12 degrees below seasonal
normals.

As for the latter part of the week, models show a trend with another
trough sweeping through the Pacific Northwest by Friday/Saturday,
pushing the ridge to our East.

&&

.AVIATION...Northwest winds at KSLC are expected to switch
to the southeast after 03z. Clouds should remain near the higher
terrain during the evening hours. Cigs are expected around 7000 ft
after 16z Saturday.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Wind Advisory until 10 AM MST Saturday for UTZ019.

WY...None.
&&

$$

SHORT TERM...Traphagan
LONG TERM/Aviation...Dewey

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http://weather.gov/saltlakecity

For frequently asked questions about the Area Forecast Discussion
visit...
http://weather.gov/saltlakecity/general/afd_faqs.php



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