Area Forecast Discussion
Issued by NWS Salt Lake City, UT
FXUS65 KSLC 202245
Area Forecast Discussion
National Weather Service Salt Lake City UT
345 PM MST Mon Feb 20 2017
.SYNOPSIS...A weak weather system will brush northern Utah
tonight, otherwise a mild and strong southwest flow will prevail
through Tuesday. A cold front Tuesday night will usher in a period
of cold unsettled weather through the end of the week.
.SHORT TERM (Through 00z Friday)...Strengthening southwesterly
flow will prevail across the forecast area through Tuesday,
downstream from a broad upper trough which encompasses the eastern
Pacific. A shortwave ejecting within this southwesterly flow aloft
is brushing northern Utah at this time, and a round of valley
rain/mountain snow will impact mainly locations north of I-80
this evening, before ending overnight.
The primary weather story through Tuesday afternoon will be the
strengthening winds, as 700mb flow is forecast to peak near 50 kts
early Tuesday morning. The pressure gradient is forecast to
continue to tighten overnight as well, and would expect to see
gusts in excess of 50 mph tonight through Tuesday across many
western valleys. As such have issued a Wind Advisory for these
locations. With the gusty south winds, temperatures overnight will
remain mild across most locations, and will see max temperatures
approach record values in some locations (record for SLC is 66 set
way back in 1879).
As the eastern Pacific trough gradually moves inland, the
associated cold front is expected to reach northern Utah late
Tuesday afternoon, then progress southward before stalling
somewhere across central Utah late Tuesday night into Wednesday.
Much cooler air behind this front will drop snow levels to most
valley floors by Wednesday. Anticipate a burst of heavy snow with
the frontal band across the higher terrain of northern Utah, and
have issued a Winter Weather Advisory for these areas, effective
through Wednesday morning.
Will likely see a lull in precipitation for much of Wednesday
aside from some lingering showers, until the main mid level trough
axis crosses the area Wednesday night into Thursday bringing
another round of snow not just to the higher terrain, but down to
the valley floors as well, as 700mb temperatures cool to near -14C
by 00Z Friday.
.LONG TERM (After 00Z Friday)...The broad trough begins to slide
east of the area late Thursday, with some showers potentially
lingering across the north through Thursday night. A flat ridge then
builds over the Great Basin on Friday and Saturday; this should lead
to a relative break in precipitation, though warming is not expected
to be particularly strong, so temperatures should remain below
The next Pacific trough pushes across California late Saturday. This
is where model agreement starts to break down, with fairly wide
variations on how quickly (or how slowly) this trough progresses
across the west. In general, however, a cool and relatively active
pattern is expected through the beginning of next week. Have
maintained somewhat high POPs across a broad area in the extended
forecast, with any real details having to wait until models come
into better agreement.
.AVIATION...Gusty south winds will continue at the SLC terminal
through the overnight hours and into Tuesday. Any precipitation
will likely hold off until Tuesday evening.
UT...Wind Advisory until 9 PM MST Tuesday for UTZ003-005-015-016.
Winter Weather Advisory from 2 PM Tuesday to 11 AM MST Wednesday
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