Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 070440

Area Forecast Discussion
National Weather Service Salt Lake City UT
940 PM MST Tue Dec 6 2016

.SYNOPSIS...A cold storm system will bring the coldest temperatures
of the season to most of Utah and southwest Wyoming through
Wednesday. This cold snap will be short lived, as a relatively mild
but active westerly flow develops late in the week through the
upcoming weekend.


.DISCUSSION...An upper trough continues to sag south into Utah this
evening with 700mb cold advection occurring over northern Utah. The
observed temperature at 700mb was -14C at SLC per 00z RAOB, but
should be down to around -16C now on its way to -18C by sunrise.
Some generally light snow will continue across the central mountains
through the books cliffs for the next few hours aided by the upper
jet through central Utah. Otherwise, cooling at 500mb is helping to
maintain a somewhat unstable airmass which is producing a few weak
showers across the northern mountains. However, low-level moisture
remains marginal so these showers have not been particularly active
thus far this evening and is not expected to increase significantly
through the rest of the night.

A concern for lake-effect showers off the GSL still exists as the
airmass is plenty cold compared to lake temperatures. However, the
lack of moisture is still a limiting factor, especially with latest
RAP BUFR soundings trending drier. Although some hi-res models such
as the HRRR and ARW continue to indicate a lake band tonight, feel
this may be a bit overdone. Cannot rule out a few showers developing
off the lake but the idea of a long-lived lake band seems rather

Otherwise, expect a cold night especially in areas where skies clear
given the cold airmass spreading into the area. Daytime temperatures
are not expected to rebound much tomorrow as most valleys outside of
far southern Utah are expected to remain below freezing and well
below climatological normals.

Updated the forecast earlier to lower PoPs and adjust Sky and have
made additional minor tweaks in the latest update.


.AVIATION...Southerly winds have developed at the SLC terminal this
evening, but may at times become variable or light north through the
night. There is a 30 percent chance of lake-effect snow developing
tonight and bring occasional MVFR/IFR conditions to the terminal.
The best chance of this occurring will be within the 09-16z





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