Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 121040
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
440 AM MDT Thu Oct 12 2017

.SYNOPSIS...A dry cold front will cross northern and western Utah
this morning then stall. The front will retreat north on Friday
then push south again Friday night and Saturday as a colder storm
system crosses the north.

&&

.SHORT TERM (Thru 00Z Monday)...A broad cold upper trof extends
from the nrn Plains to the PacNW states early this morning. This
system is moisture starved and the associated cold front is dry as
it crosses nrn UT with just a band of mid and high clouds.

The front will stall across the south this afternoon with cooler
temps and lighter winds north of the front while it stays breezy
and mild south of it. The clouds across the north should move out
of the CWA by afternoon.

The broad upper trof remains in place thru Fri with a colder short
wave dropping out of wrn Canada into the PacNW. The flow over UT
backs somewhat Fri and increases as the trof deepens to our west.
This sends the front back northward Fri aftn with the winds aloft
surfacing in most areas, and warmer temps.

The colder short wave rotates thru the base of the trof and across
nrn UT late Fri thru early Sat sending the cold front back south
again and bringing scattered showers to the north. The airmass
with this wave will be cold enough for snow to the valley floors
but do not expect much if any valley accumulation. The mountains
could pick up a couple inches, mainly north of I-80.

The short wave moves quickly east Sat morning with drying in the
afternoon and temps aloft already starting to warm back up. Sat
will be a cool day however as the warming aloft is not expected
to mix down. Sat night could be chilly in most areas in spite of
the warming aloft due to the low level cold air in place and the
expected clear calm conditions. We are forecasting the first
freeze at SLC Sun morning that could finish off any gardens in the
Salt Lake valley that have not yet frozen.

Rising heights, a warming airmass and clear skies will bring
temps back up on Sun altho warming will be sluggish due to poor
mixing.


.LONG TERM (After 00Z Monday)...Tranquil weather is expected
across the forecast area for the majority of the long term
period, as a broad mid level ridge becomes established across the
region Monday through Tuesday. This will yield a warming trend
with temperatures rebounding to near climo across the north by
Tuesday, and slightly above climo across the south.

The medium range models are in agreement weakening this ridge on
Wednesday and allowing a predominantly zonal flow to become
established across the eastern Pacific/western CONUS. However
differences between the ECMWF and GFS become obvious later
Wednesday into Thursday, as the GFS is much more aggressive
punching a strong Pacific jet into the Pacific Northwest/northern
Great Basin, potentially bringing precipitation to northern Utah
late Wednesday night into Thursday. Meanwhile the ECMWF is
considerably slower and more amplified with this feature, which
would yield a drier and more mild Thursday. For now have leaned on
the EC and kept the forecast dry through day 7.


&&

.AVIATION...Northwest winds with VFR conditions will prevail at
KSLC through the day today. There is a 20 percent chance these
winds become light and variable during the 11-14Z timeframe.

&&

.FIRE WEATHER...A dry cold front is pushing through northern Utah
early this morning and will cross the northern and western
portions of the district today before it stalls out over the
south. This front will bring cooler temperatures, higher humidity
and lower clearing indices in the stable airmass behind the front.
A westerly flow over the area Friday will bring stronger
transport winds. The front will retreat north allowing the winds
to surface in the afternoon and raising the clearing index.

A stronger cold front will sweep south Friday night into early
Saturday with a chance of snow showers over the north while the
front remains dry across the rest of the area. In the wake of
this system a dry westerly flow will bring a warming trend Sunday
through the middle of next week.

&&

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

$$

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

For more information from NOAA`s National Weather Service visit...
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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