Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 191557

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

.SYNOPSIS...A cold front is crossing 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


.DISCUSSION...Showers are continuing across northern Utah and
southwest Wyoming this morning, as a cold front has pushed through
the area. Gusty winds are ongoing this morning both ahead of and
behind the front, especially in prone locations, including windy
northwesterlies in Utah Valley. This front is not expected to make
it past central Utah, as the parent trough to the north heads due
east, eventually allowing showers to lift out of the forecast
area through late afternoon and evening. The northern half of the
forecast area should have highs about 20 degrees cooler than
yesterday, while southern Utah keeps similar temperatures to
yesterday with breezy southwest winds.

Wednesday is expected to be a warmer day, with a break between
storm systems. A stronger and colder front is forecast to move
through northern Utah Wednesday night through Thursday, producing
widespread precipitation across the north, including snow levels
dropping to about 6500 feet. This front will bring the coolest
temperatures of the fall so far, which will settle in across the
area heading into the weekend.

The forecast was updated earlier this morning to tweak the hourly
temperature curve, as temperatures had fallen a bit more than
expected across northern Utah. Otherwise, the forecast looks good,
and no further updates are anticipated. The previous long term
discussion follows.

.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
throughout the day today. Rain showers will gradually diminish at
the terminal through about 1630-1700Z. Ceilings near 5000 feet AGL
are expected to improve after 17Z. Additional showers may develop in
the vicinity of the terminal after 18Z, though any showers will come
to an end prior to 00Z. Periodic reductions in ceilings to near 5000
feet AGL will be possible near any showers this afternoon.


.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.




LONG TERM...Struthwolf

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