Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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552
FXUS65 KSLC 082326
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
426 PM MST Thu Dec 8 2016

.SYNOPSIS...A persistent and quite moist westerly flow aloft will
generate significant precipitation for northern Utah and southwest
Wyoming through the upcoming weekend. Southern Utah will remain
south of the storm track through Saturday then become unsettled
into Sunday. Monday into Tuesday a temporary ridge is expected.

&&

.SHORT TERM (Through 00z Sunday...A moist westerly flow
associated with a near zonal jet is penetrating the northern Great
Basin and northern portions of our CWA this afternoon. Weak
disturbances within this flow will cause variable intensities of
precipitation tonight through Saturday. The first disturbance is
associated with the warm front aloft moving northeast across the
region this afternoon has been the reason for the general light
snow. Temperatures behind this front will gradually warm through
tonight with pockets of cold air likely remaining into early
Friday. This complicates forecast with mixed precipitation likely
developing across the southern Wasatch Front late this evening and
working its way northward through the night reaching Brigham City
about mid morning Friday.

BUFKIT sounding for Wendover shows that a period of freezing rain
is possible between about 8 pm and 2 am tonight. This looks
reasonable as surface gradient supports a low level northeast flow
keeping a shallow cold layer in place while warm air overrides.
The rest of the forecast soundings along the Wasatch Front shows
the lowest boundary layer warming therefore the threat of freezing
rain minimal but that is not to say that pockets in certain
protected valleys couldn`t see a period of freezing rain.

Behind this warm front there is a hiatus in precipitation as seen
on the radar but this should fill in as another disturbance over
north central Nevada races eastward bringing in a better threat of
widespread precipitation after midnight. The valley temperatures
at the time that this second disturbance arrives will be critical
in the amount of snow that may occur along the Wasatch Front and
Mountain Valleys.

Temperatures will warm into the 40s along the Wasatch Front from
about Ogden southward on Friday while farther west have kept a
colder pocket in place over the west desert as it should be hard
to erase the cold air there. Snow levels expected to rise to near
7000 ft by afternoon. By Friday evening most of the precipitation
should be confined to areas north of I-80, in the northern
mountains and southwest Wyoming.

By Saturday morning the jet buckles again and another disturbance
brings cold advection in across northern portions of the CWA. Its
questionable if temperatures will get cold enough for snow in the
northern valleys other than perhaps the Cache Valley. So have kept
temps on the warm side with rain and prevailing precip in the
valleys and more snow in the mountains.

Breezy conditions may develop over southwest valleys Saturday ahead
of this northern Utah disturbance along with mild temperatures.

.LONG TERM...(After 00Z Sunday)...The cold front trailing the
short wave that is forecast to ripple past on Sat drops swd into
the CWA Sat night potentially flipping precip back to snow along
the Wasatch Front and keeping heavy snow going in the mtns. The
med range guidance starts to diverge at this point with the EC not
as cold and it also stalls the front across central UT instead of
the srn border by Sun morning. Leaned towards the colder GFS and
kept valley snow in the forecast for Sat night.

Looks like a break Sun aftn thru Mon except over the far north
then guidance brings another flat wave thru the Great Basin on Tue
with widespread precip along the baroclinic zone stretched across
the CWA thru Tue night. EC and GFS are in a little better
agreement for Wed both showing this zone lifting nwd as a warm
front thru Wed night stalling across the n Thu with most of the
CWA in the warm sector. Both then lean towards a trof deepening
over the western states Thu night into Fri with precip becoming
widespread across the CWA again.

Confidence in the details of the forecast is low but trended pops
towards these latest ideas. Bottom line is continued unsettled
thru the end of next week.

&&

.AVIATION...The SLC terminal will likely see MVFR conditions
after 02-03z in snow with a 30 percent chance of remaining MVFR
through 09Z before becoming rain. Snow accumulation of 1 inch
possible on untreated surfaces between 02z and 09z Friday.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Winter Weather Advisory until noon MST Friday for UTZ003-004-010.

     Winter Storm Warning until 4 PM MST Saturday for UTZ007>009.

     Winter Storm Warning until 3 PM MST Friday for UTZ001-002-005-
     006.

WY...Winter Weather Advisory until 3 PM MST Friday for WYZ021.

&&

$$

SHORT TERM...Struthwolf
LONG TERM...Wilensky
AVIATION...Rogowski

For more information from NOAA`s National Weather Service visit...
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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