Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 160257

Area Forecast Discussion
National Weather Service Salt Lake City UT
857 PM MDT Thu Mar 15 2018

.SYNOPSIS...The broad upper level trough across the western
states will maintain cool and unsettled conditions across Utah
this weekend. High pressure aloft will return next week and bring
a warming trend to the region.


.SHORT TERM (Through 00z Monday)...The trough rotating east-
northeast out of the parent low along the southwest Oregon coast
will split as it moves across southern/central Utah this evening.
At mid-evening sufficient instability and lift associated with
this weakening trough will generate scattered showers/isolated
thunderstorms through the balance of the evening. This activity
will become isolated across northeast Utah/southwest Wyoming late
tonight/early Friday as a weak shortwave ridge develops between
the exiting trough and the upper low near the west coast.

For Friday a few terrain-tied instability showers are about all
that will develop during the afternoon. This will all begin to
change Friday night as the coastal upper low begins a slow
eastward drift into the western Great Basin by Saturday morning.

Ahead of the main upper low the near 700mb baroclinic zone will
reach the Utah/Nevada border by late Friday night. This boundary
will likely be the focus for the initial round of light precip
triggered by the passing of the first shortwave ejecting out ahead
of the main low. The near 700mb baroclinic zone will tighten up as
it enters western Utah with precip increasing fairly rapidly along
and west of the boundary toward the center of the advancing upper
low. Anticipating a fairly widespread precip event Saturday night
through early Sunday as the core of the slowly weakening upper low
moves across the state.`Precip will wind down fairly quickly late
Sunday as the remnant of the upper moves off to the east.

.LONG TERM (After 00z Monday)...GFS and Canadian models continue to
trend with a ridge building into the Great Basin Monday night
through midweek, with the airmass gradually warming. However, the
12z and previous 00z runs of the EC have been more insistent on a
shortwave trough crossing the area Monday night. While some members
of the GFS ensemble try to bring this trough across Utah as well, in
general, most solutions have this trough weakening out before
reaching the area. Have added some slight chance PoPs Monday night
to account for possibility that the EC solution might pan out,
otherwise not making any significant changes pending better
model agreement on the details of the forecast.

The mean ridge is progged to shift east of the area Wednesday
afternoon allowing south winds to increase through Thursday.
Moisture from the Pacific looks to spread into the area ahead of the
next approaching trough, but the EC is about a half day slower in
this regard than the GFS, and all models are a bit slower than
previous runs. Regardless of the timing differences, it seems that
widespread precipitation still looks to be a possible during the
latter part of next week.


.AVIATION...A few passing showers remain possible at the SLC
terminal through around 06z with a 20 percent chance of a brief
reduction to MVFR conditions. Otherwise, expect a clearing trend in
showers and sky cover overnight. South winds will become established
by around 04z.





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