Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 171710
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
1010 AM MST Fri Nov 17 2017

.SYNOPSIS...The cold storm system over the Pacific Northwest this
morning will cross the region later this afternoon through early
this evening. High pressure aloft will return to the region this
weekend.

&&

.DISCUSSION...The upper level trough currently positioned across
the Pacific Northwest will continue east across the northern
Rockies/northern Great Basin this afternoon through early this
evening. Trailing this trough will be a low amplitude upper ridge
which will encompass most of the western CONUS this weekend.

The surface cold front associated with the approaching upper
trough is just south of KPVU (Provo) and is moving slowly south
at this time. Behind this surface boundary light/moderate
intensity precip remains concentrated along the near 700mb
baroclinic which is stretched out from central Nevada east-
northeast into extreme southern Wyoming.

Low-level forcing into the baroclinic zone supported by weak mid-
level shortwaves and fairly strong upper divergence between the
coupled polar/subtropical jets has created deep lift capable of
supporting embedded convection. This favorable scenario for deep
lift should persist through early this afternoon.

As the Pacific Northwest trough nears Utah the low-level
baroclinic zone will become more frontogenic as low-level cold
advection increases immediately ahead of the advancing mid-level
trough. Precip will likely transition from stratiform to
convective as the air mass destabilizes with the arrival of the
mid-level cold pool, strong low-level forcing and supporting mid-
level dynamic lift and solid upper divergence generated by the
upper jet. Intense, but relatively sort duration convective precip
is likely along and immediate behind the now accelerating
baroclinic zone, with scattered and loosely organized convection
embedded in the mid-level cold pool back across northern Utah.

The low amplitude upper ridge trailing the exiting trough tonight
will bring a quick end to any convection during the overnight
hours. Cold temperatures are expected by Saturday morning, with
the potential for valley fog across the north resulting from the
clearing skies, light winds and very moist boundary layer
conditions.

Current forecast trends look good. No update planned at this time.

&&

.AVIATION...At the SLC terminal, conditions are expected to bounce
between low-end VFR and high-end MVFR through the morning and early
afternoon in rain showers. Conditions will become prevailing VFR as
the showers diminish, most likely between 20Z and 22Z. Occasionally
gusty northwest winds are expected to persist through the daytime
hours.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Wind Advisory until 9 PM MST this evening for UTZ013-020-021.

     Winter Weather Advisory until 5 PM MST this afternoon for
     UTZ007>010.

WY...None.
&&

$$

PUBLIC...CONGER
AVIATION...TRAPHAGAN

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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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