Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 180337
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
937 PM MDT Thu Aug 17 2017

.SYNOPSIS...A warming and drying trend will continue across the
area through Friday. Moisture will increase again from the south
beginning late in the weekend and continuing into early next
week.

&&

.SHORT TERM (THROUGH 12Z SUNDAY)...The increasingly dry northwest
flow aloft has pushed much of the moisture out of the northern and
central Utah and into the south. A weak convergence area across
the south will keep this moisture in place, and will likely be the
area where any showers/storms develop Friday. Across the rest of
the state enough moisture will linger for terrain-based cumulus,
with little or no real chance for precip outside of the eastern
end of the Uinta range.

The slow development of the upper low circulation off the
southern California coast will produce development of a better
organized deformation axis across southern Utah Friday night
night/Saturday. Convection will likely focus on the deformation,
though the areal coverage and intensity of said convection will
likely remain limited.

The breakdown of the deformation axis Saturday night will allow
moisture to advect north across much of the remainder of the
forecast area. Convection, lacking any significant dynamic or
thermal support, will generally remain isolated in areal coverage
overnight.

.PREVIOUS LONG TERM (After 12z Sunday)...The upper level low is
forecast to remain mostly stationary off the California coast
through mid week, while moisture is transported northward into
southern and central Utah through the week. With several
shortwaves rotating up from the southwest through southern and
central Utah starting Monday, the overall pattern through the week
looks quite unsettled for convection each day.

Overall upward trend in the PoP forecast through the extended. The
slowness of the GFS to eject the upper Low from the
Nevada/Utah/Arizona triple-point area and the ECMWF similar
pattern through Thursday, differences aside, made me lean towards
a more unsettled solution. The previous model runs of the GFS seem
to be in better agreement compared to the previous versions of
the EC, so leaned a bit more towards the GFS, which ironically is
a bit of a wetter solution. Confidence of timing and exact
location of the best opportunity for precipitation and convection
is low, but the pattern definitely has more moisture drawn
northward into Utah from the monsoon pattern. Temperatures in the
extended seem to remain mostly unchanged even with this pattern;
just enough daily instability and convective cloud cover to help
temperatures remain near seasonal normals.

&&

.AVIATION...The dry/stable air mass across northern Utah will
maintain VFR conditions under clear skies during this TAF period.
Light southeast drainage winds will persist through Friday
morning before turning to the northwest for the afternoon.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...None.
WY...None.
&&

$$

CONGER/DEWEY

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