Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 201620
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
1020 AM MDT FRI MAY 20 2016

.SYNOPSIS...Strong southerly flow will develop today ahead of the
next Pacific storm. This system will slowly cross the Pacific
Northwest and Great Basin through the weekend.

&&

.DISCUSSION...
Water Vapor loop shows a broad deep closed low centered over
Northern California. AMDAR 400-200MB wind observations place a
75-115kt cyclonic jet over Central California into the Northern
Rockies. GOES/HRRR/00Z KSLC RAOB indicate the precipitable water
value ranges from 0.25"-0.35" mountains to 0.60"-0.90" valleys.

Two main concerns today are synoptic wind and convection.

RAP indicates a deep 992mb cyclone makes its way into NW Utah this
afternoon. Winds across far Northwest Utah will be substantially
lower than points further South. There is a 8MB Southerly gradient
in place with 50kts of 700mb flow and 5-8mb of pressure falls.
The only negative for winds is the extensive mid and high clouds.

Added Wind Advisories for the Central and Southern Mountains as
they could easily hit 60+ mph gusts for several hours this
afternoon.

Models in good agreement that far NW Utah and areas east of the
Wasatch could see some convection today. Given instability and
shear parameters from the Short Range Ensembles along with
strengthening flow, convection needs to be monitored for severity.

&&

.PREVIOUS DISCUSSION...
The deep upper low is re-centering itself over nrn CA early this
morning with the flow over UT and the Great Basin backing to more
southerly. The frontal boundary associated with the widespread
precip across the north earlier tonight is retreating north as
forecast and winds are flipping back to southerly south of about
i-80.

These winds are still forecast to reach warning levels across much
of wrn UT by midday as the upper low translates slowly east and
the strongest flow aloft east of the low aligns over wrn UT.
Advisory level speeds are also still expected across the south and
southeast as well as the normally less windy areas of the west.
Current wind highlights appear on track.

Any precip today looks to be limited to the far nw and the nrn
mtns. The cold front edges back into the CWA tonight thru Sat as
the upper low shifts east spreading isolated to scattered showers
across the northern and central CWA.

The low opens up and lifts into the nrn Rockies Sat night with
cool moist westerly flow for Sun keeping showers active across the
north. Expect a break Sun night into Mon as a new short wave trof
deepens to our west.

A mean longwave trough will continue to orient over the interior
west through much of the long term period. Embedded waves within
this cyclonic flow will translate across the area roughly once a
day through Thursday maintaining a chance of showers and isolated
storms over the north, but largely dry conditions are anticipated
across the south where a drier southwesterly flow aloft will limit
convective potential. Do not foresee much of an impact from any
one wave as vertical profiles remain conditionally unstable and
shear currently forecasted to be weak each day. PWAT at or below a
half inch as well should limit rainfall potential as well.

Differences in trough evolution are apparent during the latter
half of next week as the GFS attempts to maintain cyclonic flow
into the weekend, whereas the ECMWF phases more towards a zonal
flow. Limited confidence exists in any one solution attm.

Temperatures will trend near climo then hover around normal levels
through day 7.

&&

.AVIATION...Strong southerly winds will begin developing at kslc
between 16-18z and continue increasing into the afternoon. After
18z, sustained wind speeds in excess of 30 kts are likely with gusts
in excess of 50 kts possible. Blowing dust remains a concern during
the periods of strongest wind speeds this afternoon, with a 60
percent chance of vis reductions into the mvfr category. Winds will
decrease rapidly between 00-03z this evening.

&&

.FIRE WEATHER...A widespread Spring storm will bring very strong
Southerly winds today with low RH especially the Western Valleys.
Isolated to Scattered convection will be relegated to far NW Utah
and east of the Wasatch this afternoon.

A cooling and moistening trend begins tomorrow from NW to SE.
Southeast Utah will still see gusty Southerly winds along with low
RH. Convection should be similar in nature to today.

The cool unsettled pattern will remain in place Sunday with much
less in the way of winds.

&&

.SLC Watches/Warnings/Advisories...
UT...Wind Advisory until 10 PM MDT this evening for UTZ002-004-013-
     014-019>021-517-518.

     High Wind Warning until 10 PM MDT this evening for UTZ003-005-
     015-016.

WY...None.
&&

$$

PUBLIC...ROGOWSKI/WILENSKY/MERRILL
AVIATION...RUTZ
FIRE WEATHER...ROGOWSKI

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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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