Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 142200
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
400 PM MDT Sat Apr 14 2018

.SYNOPSIS...High pressure aloft across the Great Basin will bring
a warming trend to Utah through Sunday. The next Pacific storm
system will impact the region early in the upcoming work week.

&&

.SHORT TERM (Through 00Z Wednesday)...Upper level ridging is
centered over the Great Basin this afternoon, leading to sunny to
partly cloudy skies across most of Utah and southwest Wyoming, and
temperatures near normal for mid-April. This warming trend will
continue on Sunday, as the ridge axis shifts over Colorado and
southwesterly flow begins to increase across the Great Basin.
Increased mid and high level cloud cover tomorrow may limit high
temperatures by a couple degrees, but in general mixing should be
sufficient to allow temperatures to climb nicely.

Southwest winds will begin to increase significantly late Sunday
into Monday as a Pacific trough begins pushing inland, and the
surface low tracks across northern Nevada and northern Utah.
This decent surface gradient, coupled with 40-60 knot winds at
700mb, should create windy conditions across the area, especially
in western Utah through the day Monday. One limiting factor with
this wind event, when compared to the one that happened a few days
ago, is that the surface low is not really deepening as it moves
into the area, and instead is relatively steady state pressure-
wise as it traverses the state.

All of this said, have hoisted a high wind watch for west-central
and southwest Utah on this shift, for Monday morning through
Monday evening. There is some concern that the strong winds could
begin Sunday night or earlier on Monday morning, but there will be
an opportunity to tweak the timing before upgrading the watch to
an advisory/warning if necessary. Other locations will likely
need headlines in the future for this wind event, especially the
northwest desert and the Sevier Valley, but those locations are
somewhat lower confidence, so have not included them at this
time.

The cold front associated with this storm stalls a bit over
northwest Utah early Monday, before sweeping across the state
Monday afternoon through Monday night. This is another cold front
with a tight baroclinic zone, and should bring a round of
precipitation with this low level forcing, but the heavier precip
amounts may hold off until the lagging upper level support moves
over the area early Tuesday morning. This front will bring snow
levels down to the valley floors across the northern two thirds of
Utah by Monday night. Precipitation looks to taper off through
the day Tuesday; the trough axis shifts quickly east of the area
by 18Z Tuesday, though mountain showers could linger a bit longer
in the moist northwest flow. Either way, current timing indicates
that conditions should stabilize quickly after 21Z Tuesday as
ridging re-builds over the Great Basin.


.LONG TERM (After 00Z Wednesday)...General overall pattern fairly
consistent between global models in the long term. A ridge is
forecast to build into the area from the west Tuesday night into
Wednesday bringing a return to warmer and drier conditions with
lighter winds. The next storm system will then cross the area as a
closed low during the latter half of the week.

The 12z GFS and EC are in remarkably good agreement regarding the
approach of the low on Thursday, considering the increased
uncertainty inherent with closed lows. Run-to-run consistency is
still something to contend with, but details should become clearer
with time. However, given the latest trends, the slower solution is
being favored, and precipitation is not expected to really develop
until Thursday evening/night. However, given northeasterly flow
along the northern periphery of the low, precipitation does not
appear to be very favorable for the Wasatch Front Thursday night.
West-central and southwest Utah seem to be a better bet given more
favorable upslope flow.

The GFS and EC start to diverge during the day Friday regrading the
egress of the upper low. The GFS is faster and lifts the low center
a bit farther north than the EC. As a result, the GFS brings in a
period of northwesterly flow aloft that would be favorable for the
Wasatch Range and adjacent valleys, whereas this is not the case in
the EC. Still, expect a period of wet weather for a good portion of
Utah with this storm late Thursday into Friday. Snow levels are
likely to remain off most valleys as the airmass will remain on the
mild side.

&&

.AVIATION...Northwesterly winds at the SLC terminal are expected to
shift to the southeast between 02-03Z.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...High Wind Watch from Monday morning through Monday evening for
     UTZ015-016.

WY...None.
&&

$$

SHORT TERM...Schoening
LONG TERM...Cheng
AVIATION...Kruse

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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