Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 161614

Area Forecast Discussion
National Weather Service Salt Lake City UT
1014 AM MDT Wed Aug 16 2017

.SYNOPSIS...The weak upper level trough over Nevada will cross
Utah tonight through Thursday. Limited moisture will linger
Friday, then increase again from the south over the weekend.


.DISCUSSION...The diffluent upper trough currently centered on
Nevada will work slowly east into and then across Utah tonight
through Thursday. Water vapor imagery shows the main vorticity
max embedded within the trough moving southeast along the spine of
the Sierras, with a eventual track into western Arizona Thursday.

The extensive mid-level moisture field associated with the trough
will eventually spread into Utah later today. The best area for
convection appears to be over the southern half of Utah. Sufficient
moisture combined with the advancing vorticity max and a
developing upper jet along the Arizona border should generate the
necessary lift for isolated to scattered convection this afternoon
and evening. Up north convection will struggle as advancing cloud
cover will inhibit surface heating and moisture remains somewhat
limited. Will maintain isolated convection across the northeast
mountains, with little else across the remainder of the north.

A west-to-east mid-level deformation axis that develops across
southern Utah late Thursday night/Friday will serve as the focus
for additional convection near the Arizona border. Areas to the
north will be under a substantially drier west-northwest Friday.

Moisture will return north this weekend in response to the
development of an upper low over/near the southern California
coast. This moisture will be somewhat constrained by the
deformation axis to the north of the upper low. This axis will
reach central Utah Saturday, then dissipate and allow moisture to
continue across the remainder of the state Saturday night/Sunday.

Cloud cover remains the big issue during the eclipse on Monday.
The above mentioned upper low will become better defined along the
southern California coast this weekend. The southerly flow on the
eastern flank of the upper low will continue to advect moisture
northward, with some degree of cloud likely. A shortwave ridge
over northern Utah Monday morning suggest subsidence and possibly
a minimum in coverage of clouds during that period.

No update planned for the early morning forecast package at this


.AVIATION...The SLC terminal will see VFR conditions through the
day. Any CIGS that develop will be high. Southeast winds are
expected to shift to the northwest between 18Z and 20Z.





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