Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 222208
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
408 PM MDT Mon May 22 2017

.SYNOPSIS...High pressure aloft will expand east across the Great
Basin Tuesday, then shift east of the area on Wednesday. The next
series of weather disturbances off the Pacific will first impact
Utah late Wednesday, with additional disturbances through the
first half of the upcoming weekend.

&&

.SHORT TERM (Until 06z Friday)...The upper ridge positioned across
the west coast states this afternoon will expand east across the
Great Basin by Tuesday. This ridge will continue the warming trend
of today, with most areas of Utah warming above their late May
norms.

The residual moisture as defined in the GOES PWAT imagery across
northeast Utah/southwest Wyoming has spawned an extensive area of
terrain- based cumulus this afternoon. Daytime heating the
driving force for the cloud development, with sufficient
differential heating over the higher terrain possibly producing a
few showers late this afternoon. Clouds and any showers should
dissipate fairly quickly this evening with the loss of daytime
heating.

The next storm system currently over the Gulf of Alaska will
continue southeast into the Pacific Northwest/northern Rockies by
early Wednesday. The core of this feature will remain well removed
to the north of Utah over southern Canada as it track east late in
the week. A series of what look to be energetic vorticity lobes
rotating around the parent upper low will cross through northern
Utah/southwest Wyoming beginning late Wednesday night/Thursday,
and continuing beyond the short term forecast period.

The associated low-level baroclinic zone nudged into northern
Utah by the first of these vorticity lobes will serve as the focus
for convection late Wednesday night/Thursday. Convergence into
this low-level thermal boundary supported by the dynamic lift and
modest cooling in the mid-level will generate scattered
convection. Moisture is somewhat of a limiting factor, so not
anticipating much on the way of heavy precip outside of isolated
stronger storms over the higher terrain Thursday afternoon and
evening.

.LONG TERM (After 06z Friday)...Remnant frontal boundary draped
across central Utah Thursday night will remain either nearly
stationary heading into Friday (ECMWF) or lift slightly north with
baroclinicity focusing over northern Utah during the morning (GFS).
The subtle differences in placement during the morning hours only
factors into initiation time and placement of any convective
development and a few degrees temp through midday, as the next lobe
of the long wave trough will be poised to drop into northern UT
during the afternoon. Both solutions place the front over central UT
by the afternoon regardless, so these details for now remain
somewhat of a moot point in the long range. Have maintained
generally isolated to widely scattered convection across the
northern half for the day, largely diurnal.

This final lobe of the longwave trough will continue to carve
southeast across the area through Saturday with convective
development most likely along the cold front as it eventually slides
across Castle Country, and over the higher terrain of the
northern/central mtns. Have started to expand PoPs to have a mention
in the southeast as such.

Beginning Sunday a transition period will begin with encroachment of
a mid level ridge building in from the west. Though details
regarding breadth of warming are noticeable in globals (EC a few
degrees warmer each day), the big picture takeaway for the remainder
of the long term period points towards warming trend temps and
stable conditions.

&&

.AVIATION...The SLC terminal will be under mostly clear skies
through the valid TAF period. Winds should remain diurnally driven,
switching from the northwest to a southeast direction between 03z
and 04z this evening.

&&

.FIRE WEATHER...High pressure aloft will expand across the entire
Great Basin for Tuesday. This high will continue the trend of
warmer temps, low humidities and generally light winds. This high
pressure aloft will move east out of Utah late Wednesday ahead of
the next Pacific storm system settling into the Pacific Northwest
and northern Rockies.

The core of this next storm will remain well removed to to the
north north as it track slowly east near the Canadian border.
Disturbances rotating around the main storm will nudge a cold
front into northern Utah Wednesday night, with this front settling
into central Utah at the end of the week. Significantly cooler
temps and modestly higher RH values will follow the front.
Scattered showers and isolated thunderstorms are expected along
and trailing the front, with wetting rains generally confined to
the higher elevations of northeast Utah.

Strong high pressure aloft will become established once across the
western states beginning Sunday, and remaining in place through
around midweek. Very warm temps and low Rh values are expected
during that period.

&&

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

$$

SHORT TERM/FIRE WEATHER...CONGER
LONG TERM...MERRILL
AVIATION...DEWEY

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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