Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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310
FXUS65 KSLC 221031
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
431 AM MDT Thu Jun 22 2017

.SYNOPSIS...A drier northwest flow will settle into the area today
with cooler temperatures across the north. High pressure will
redevelop for the early part of next week.

&&

.SHORT TERM (Through 12z Saturday)...Short wave energy translating
east across the northern Rockies states has transitioned the
northern portions of the forecast area into a slightly cyclonic flow
aloft, with a shallow surface boundary pushing south into central UT
at this time. Sensibly, the biggest take away from passage of this
feature will be a net cooling of some 10 degrees across the northern
half within an enhanced N-S MSLP gradient, but the far south will
note little if any change in temps etc. from the last few days.

SPC SREF, HRRR, and NCAR ensemble do advertise a window of
instability developing early this afternoon across the far eastern
mtn spines in the Uintas and Book Cliffs, but do not feel this
convective potential will linger nor promote much potential for
storms. Have some token 20% PoPs for these areas, but as a whole we
are evolving into a drying/stabilizing environment in wake of the
boundary, and the transition in flow aloft dominated by the northern
branch.

Dry and stable conditions will be maintained through the end of the
week thereafter, with the net N-S MSLP gradient suppressing both
moisture/instability south and east of the area. Said cooling of 10
degrees or so from yesterday`s highs will continue to be realized
largely north of I-70 again on Friday, but far southern portions
will remain well above average.

.LONG TERM (After 12z Saturday)...A dry northwesterly flow aloft is
forecast to remain in place on Saturday with temperatures changing
little from Friday. High pressure will then build into the Great
Basin Sunday into Monday, with temperatures trending warmer again
across northern and central Utah. Meanwhile, temperatures will
remain quite warm across the south.

Some midlevel moisture is progged to spread into the area Sunday
night which could result in some high-based convection Monday. This
moisture and associated convective potential looks to remain in
place through Tuesday before drier air spreads in from the northwest
in the wake of a shallow cold front associated with a weak shortwave
trough. Temperatures will start trending downward on Tuesday, but
after that model spread increases with the GFS and EC trending in
opposite directions for the second half of the week. The GFS
indicates a continued cooling trend as a stronger secondary trough
carves into northern Utah while the EC re-builds a ridge over the
area.

&&

.AVIATION...Northerly winds are expected to persist at the SLC
terminal through the day, though periods of light and variable winds
are possible early this morning. Otherwise, VFR conditions are
expected throughout the day.

&&

.FIRE WEATHER...The primary fire weather concern over the next 24
hours hones in on critical wind potential and bone dry RH across
many eastern/southern areas where fuels are cured and the Haines
remains projected at a 6. Red Flag Warnings remain in place for the
susceptible areas where fire growth and/or maintenance is most prone
in these areas. See RFW/FWF for further details on specific fire
weather zones and elevations. This threat will be greatest during
the peak heating hours focused between noon and 10pm today.

The shallow boundary working south into central/southern Utah
driving this heightened wind potential will promote cooling across
the northern portions of the district with temps peaking some 10
degrees or so cooler today vs. the last few. This said, breezy (sub
critical) northerly winds and low RH can be expected across the
northwestern valley areas as well.

Wind trends will back off come Friday as support in wake of the
boundary passage will begin to wane. Can not rule out isolated
critical winds/RH across some of the prone downslope/mountain areas
in the southeast Friday afternoon, but trends in guidance points
towards threshold values not being met attm. Will continue to
monitor.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Excessive Heat Warning until 10 PM MDT this evening for UTZ021.

     Excessive Heat Warning until 10 PM MDT Sunday for UTZ019.

     Red Flag Warning from noon today to 10 PM MDT this evening for
     UTZ482-484-488-489-493-494-496-498.

     Heat Advisory until 10 PM MDT this evening for UTZ013-020.

WY...None.

&&

$$

Merrill/Cheng

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http://weather.gov/saltlakecity

For frequently asked questions about the Area Forecast Discussion
visit...
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