Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 240344
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
944 PM MDT Thu Mar 23 2017

.SYNOPSIS...A Pacific storm system will exit Utah overnight,
followed by high pressure aloft for Friday. A new Pacific weather
disturbance will arrive this weekend, followed by another storm
system during the first half of next week.

&&

.SHORT TERM (Through 00z Monday)...The prolific upper trough that
brought widespread moderate to heavy valley rain and mountain
snow to most of the state has moved east into the central Rockies
this evening. Clearing/drying will take hold overnight as high
pressure aloft moves east across the Great Basin. Temps should
bounce back Friday afternoon as an increasingly warm southwest
flow aloft develops as the upper ridge slides east of Utah.

The next Pacific upper level trough currently off the Pacific
Northwest/BritCol coasts will follow the exiting upper ridge,
reaching Utah late Saturday. This trough will split as it moves
inland Friday night, with more of the energy remaining with the
northern split across the Pacific Northwest/northern Rockies.

The southern split, though not as well put together in terms of
baroclinic structure, will still bring sufficient dynamic lift
and cold air aloft to generate enough synoptic-scale lift for
scattered precip along and ahead of the trough axis late Saturday
through Saturday evening. Ridging behind the passing trough should
quickly end any lingering precip late Saturday night, with
generally dry conditions and mild temps to follow for Sunday.

.LONG TERM (After 00z Monday)...The active weather pattern looks
to continue through the long term period, as a Pacific trough will
begin to impact the state during the day on Monday. Although all
guidance depicts this feature, there are significant differences
in its amplitude, projected track/speed and consequently its
impacts on sensible weather. The GFS is the most amplified and
slowest solution, first transitioning the Pacific wave into a
closed low early Mon and then digging it down to the
Arizona/Mexico border Tues/Wed. This solution would likely result
in the best precip being focused over Southern and Central Utah
during the Tue/Wed timeframe, although some precip is also
possible on Monday in western Utah near a stalled mid-level
boundary and over the Central Utah mountains due to moist
southwesterly flow. Furthermore with the GFS solution the coldest
temps would be pinned much further south, and northern Utah would
experience a period of warm advection Tues/Wed raising temps to
near climatology.

The EC and (especially) the Canadian are less amplified and faster
with this feature driving a cold front through Northern/Central Utah
late Monday/early Tuesday. This would result in more precip for
Northern Utah and also significantly cooler temperatures. Even with
this cooler solution, snow levels would likely remain above valley
floors in Northern Utah, although the Canadian solution would
potentially bring slow down to the benches (i.e. 5000-6000 foot
zone). For this forecast package leaned towards the EC/Canadian
solution and consequently cooled temps a bit, raised PoPs for the
Mon-Tues timeframe, and backed off some on PoPs for the Tues/Wed
timeframe. The caveat being that due to the aforementioned
differences in guidance significant modifications to these
forecast parameters may be necessary in subsequent updates
depending on model trends.

After the first system moves out (either Wed or Thurs depending on
which solution verifies) there will be a brief respite until another
Pacific trough begins to deepen just upstream of the forecast
area. Although a cool down and precip appear likely with this
system, details are tough to nail down at this point, thus went
with a simple model blend for PoPs and went just below climatology
for late week temps.

&&

.AVIATION...The bulk of the cloudiness and associated precip has
moved out of the KSLC terminal, consequently VFR conditions are
expected to prevail overnight. Winds will be light and generally
southerly through the overnight period, although there is a 20
percent chance of a temporary shift to the northwest in the 03-08Z
timeframe.

&&

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

$$

SHORT TERM...CONGER
LONG TERM/AVIATION...CARR

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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