Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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039
FXUS65 KSLC 131011
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
411 AM MDT Fri Oct 13 2017

.SYNOPSIS...A dry and mild westerly flow will be over the area
today. A strong cold front will cross Utah tonight with some
moisture over the north. A colder northerly flow will follow the
front on Saturday. Dry high pressure will build into the region
for the first part of next week bringing a warming trend.

&&

.SHORT TERM (THROUGH 00Z TUESDAY)...A broad cold upper trof
continues to cover the nwrn CONUS early this morning extending
from the nrn Plains to the PacNW. Skies across the CWA are clear
with just some thin cirrus across the south.

A short wave dropping into the wrn side of this trof will deepen
the trof to our west backing and increasing the flow over UT
today with warming temps and breezy aftn winds. The entire trof
continues to sharpen up and swings east tonight as upstream
ridging advances from the Gulf of Alaska.

This trof is somewhat moisture starved and any precip is mostly
confined to the cold pool aloft which is forecast to just clip nrn
UT as the axis passes tonight.

There will be a strong push of cold air at lower levels from this
system with a vigorous cold front crossing the CWA tonight thru
Sat morning. Any precip will remain confined to the northern CWA,
with generally light amounts expected. Snow levels will lower to
the valley floors but with no valley accumulation.

Gusty post frontal winds could nudge into the advisory range in
the lee of the Wasatch Plateau in Carbon and Emery counties for a
time early Sat but the window for the strongest winds looks
brief. The other area with a potential for stronger winds is the
gaps in Washington county but the tight surface gradient and low
level cold advection is not supported by winds aloft and speeds
may end up short of advisory levels. Have opted to hold off on any
wind highlights at this time.

The upstream ridge builds into the Great Basin Sat aftn thru Sun with
rapid warming and stabilization aloft. The cold air at low levels
stays in place however and a good radiative night Sat night should
allow temps to dip to chilly values. We are still forecasting the
first freeze at SLC and this will likely kill any unprotected
gardens along the Wasatch Front that have yet to freeze.

Strong warming aloft continues into Mon under dry ridge conditions
but warming at the surface will be sluggish.


.LONG TERM (AFTER 00Z TUESDAY)...Mid level ridging which is
expected to encompass much of the western CONUS at the beginning
of the long term period is forecast to quickly flatten by midweek,
as a progressive pattern sets up across the eastern Pacific into
the western CONUS. The 00Z GFS and ECMWF remain in some
disagreement, with the GFS remaining more aggressive translating
both the northern stream jet as well as a southern stream low and
associated moisture into the interior west, while the ECMWF
remains slower and weaker with these features. Have leaned toward
the ECMWF, and held off on introducing PoPs until late in the
week. Temperatures should remain mild throughout much of the week,
running a bit above climo through Thursday before cooling on
Friday.

&&

.AVIATION...Southerly winds at KSLC are expected to switch to the
northwest during the 18-19Z timeframe, with a 30 percent chance
this wind shift holds off until after 20Z. VFR conditions will
prevail through the day.

&&

.FIRE WEATHER...A westerly flow over the area today will bring
stronger transport winds, warmer temperatures and improved
clearing indices. These winds will surface in most areas today
with locally windy conditions developing. A strong cold front will
sweep south across the district tonight through early Saturday
with a chance of snow showers over the north while the front
remains dry across the rest of the area. Locally gusty north to
northwest winds will follow the front and continue through most of
Saturday. The strongest winds are expected along the eastern and
southern slopes of the mountains in eastern and southern Utah. Dry
high pressure will build into the district starting Sunday and
continuing through Tuesday. This will bring a gradual warming
trend but also poor clearing indices due to the stable conditions
and light transport winds.

&&

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

$$

SHORT TERM/FIRE WEATHER...Wilensky
LONG TERM/AVIATION...Seaman



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