Area Forecast Discussion
Issued by NWS Salt Lake City, UT
FXUS65 KSLC 280243
Area Forecast Discussion
National Weather Service Salt Lake City UT
843 PM MDT Thu Apr 27 2017
.SYNOPSIS...A cold upper low will form over northeast Utah late
tonight then move south to near the Four Corners by Friday
evening. The low will then move off to the southeast on Saturday.
A weaker and warmer system will cross mainly northern Utah late
Sunday into Monday.
.DISCUSSION...A cold upper trof extends from the northern Rockies
into the nrn Plains this evening with UT under a cold nwly flow.
Instability rain and snow showers were active across nrn and
central UT today and continue into this evening altho they are
becoming a little more isolated with the loss of daytime heating.
The cold trof is forecast to close off into a low centered over
wrn NE with a second center over nern UT by 12z Fri. The UT center
is then forecast to drop south to near the 4 corners during the
The airmass looks to remain unstable enough to support isolated
showers from late this evening thru the early morning hours
across the nrn and central CWA. A wrap around band of moisture
spreads into nrn UT late tonight thru Fri morning in the wake of
the UT low center. This should bring a significant increase in
shower coverage from north to south thru the morning with
scattered showers persisting thru Fri aftn and Fri night.
The airmass is plenty cold enough for precip to fall as snow at
all elevations except the far south with a threat of accumulating
snow along the Wasatch Front valleys. There is a possibility that
enough could fall to break tree limbs from the added weight of the
snow on leafed out trees but it remains very uncertain just how
widespread this will be, or if that much even falls. Will continue
to hold off on issuing any winter weather highlights. Valley
roadways could briefly slush up in the morning if the heavier
snow showers do materialize but by midday all roads should be
running just wet. Routes thru the mtns could become briefly snow
packed in the morning but here too this should only be an impact
during the times of heaviest snow.
Gusty northwest winds will continue for a few more hours this eve
then diminish altho they will probably not completely drop off
overnight. The winds look to increase across Washington Co as the
low level cold air pushes south this evening with locally strong
winds blowing thru the gaps overnight. Existing Wind Advisory for
this will remain in effect.
As the flow aloft turns easterly Fri night in the wake of the
departing low, local gusty canyon winds could develop along the
Wasatch Front, lasting into Sat morning. Conditions do not look
favorable for a strong wind event but it could be quite gusty for
a time. The northeast winds will also redevelop across Washington
County during this same time altho the surface gradient does not
appear to be as favorable as tonight.
Winds and clouds should keep temps out of the hard freeze range
tonight and possibly again Fri night but many spots will dip to
near or below freezing both nights. The current guidance
indicates mid and high clouds will get thick enough across the CWA
Sat night to prevent a widespread hard freeze that night as well.
Updated forecasts earlier to add mention of snow to evening valley
showers and remove mention of rain after midnight. Also raised
pops somewhat across the northern and central CWA overnight.
No additional updates planned at this time.
.AVIATION...Passing showers will continue to bring a threat of
brief CIGS blo 6000 ft to the SLC terminal through the evening.
Snow showers are expected to increase later tonight into Fri
morning with occasional IFR conditions possible. Any accumulation
on untreated surfaces is expected to remain below 1 inch. The
chance of a lake band developing over the airfield bringing
greater accumulation is 20 percent.
UT...Wind Advisory until 6 AM MDT Friday for UTZ019.
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