Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 191122

Area Forecast Discussion
National Weather Service Salt Lake City UT
522 AM MDT Tue Sep 19 2017

.SYNOPSIS...A cold front will cross northern and central Utah
today. A colder upper trough will move into Utah starting late
Wednesday night and will linger over the area through the upcoming


.SHORT TERM (Thru 00Z Friday)...An upper trof is moving into the
nrn Rockies early this morning with the axis upstream over
central NV. The associated cold front is working into nrn UT and
is passing SLC at this time. Showers along and north of the front
have persisted overnight and expect these to continue through most
of the morning from about Provo north.

Showers will taper off rapidly once the trof axis passes around
midday along with some clearing. Snow levels have dipped to near
8000 feet in the nrn mtns and several inches accumulation is
possible above about 9000 ft.

The cold front will work south thru the CWA today stalling over
srn UT tonight. Temps across the north will be about 20 deg cooler
than yesterday while the south stays warm. Gusty swly winds ahead
of the front will persist today with gusty nw winds behind it for
a time this morning.

The flow backs around to swly on Wed as the next cold trof digs
into the PacNW. The stalled cold front lifts north as a warm front
in the morning to a position across far nw UT by 00z Thu.
Southwest winds increase across the CWA Wed aftn and temps warm
back up to near normal across the north.

The front over far nwrn UT Wed eve begins to edge back southward
as a cold front as the upstream trof moves inland. A broad swath
of precip is forecast to develop along and north of the front Wed
night that follows it thru the CWA as it moves slowly southeast.
The front reaches SLC early Thu but it looks like the rain holds
off until afternoon to reach that far south. Precip should be just
starting to spread into swrn UT late in the day. Winds ahead of
the front will get strong over southern and ern UT in the aftn.

.LONG TERM (After 00Z Friday)...The EC continues to be the model
of choice through the extended. Noticed that the 00Z GFS
ensemble actually resembled the EC more so than it did the GFS
operational run. The combination of a good 700mb baroclinic zone
stretching from southwest Utah to southwest Wyoming and a decent
jet aloft should provide for good vertical motions between 00Z and
06Z Friday. Have increased PoPs to likely under this swath. Snow
levels will lower to about 7500ft across northern mtns by 06Z and
to 7000ft by 12Z. The central and southern mtns will have snow
levels lowering to about 8500-9000ft by 12Z Friday. The
baroclinicity weakens overnight into Friday as the trough moves
east so have only boosted PoPs to likely in some mountain
locations which may need to be adjusted upwards if the baroclinic
zones holds together a little better since the jet aloft is still
in place.

Unlike the GFS, the EC has the 500mb cold pool lifting
northeastward Saturday afternoon into Saturday night with 500mb
mb vorticity advection which supports keeping scattered showers
going across the northern 1/2 to 2/3 of the CWA into Saturday
night. The EC shows a drier and warmer NW flow developing Sunday
into early next week as it pulls the trough NE into the Plains
compared to GFS which holds the cold upper circulation much closer
over SW Wyoming. Once again the progressive pattern we are in
would suggest that the EC is more correct in moving the trough
eastward faster.

Temperatures will be about 15-20 degrees below normal Friday
through Saturday before a gradual warming trend occurs. Dry
conditions are expected after Sunday evening across the entire


.AVIATION...Northwest winds are expected at the SLC terminal today
along with VFR conditions. Showers through about 18-20Z will cause
cigs to lower at times below 7000k ft AGL through 19Z with a 40
percent chance of lingering through 21Z.


.FIRE WEATHER...A cold front will cross northern and central Utah
today with showers and cooler temperatures while the south stays
breezy and mild. The front will stall across southern Utah tonight
then dissipate on Wednesday as south winds pick up again. It will
be windy with warmer temperatures area wide on Wednesday ahead of
the next cold front. This front will be stronger and is forecast
to move slowly across the district Wednesday night through
Thursday night. Expect widespread valley rain and mountain snow
over the north and west with precipitation becoming more showery
on Friday. Strong winds will develop south of the front on
Thursday. Much cooler temperatures will follow the front into the
region with highs Thursday behind the front falling over 20
degrees from Wednesday. Cool and unsettled conditions are expected
to continue through at least the upcoming weekend.





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