Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 252132

Area Forecast Discussion
National Weather Service Salt Lake City UT
332 PM MDT Sun Jun 25 2017

.SYNOPSIS...High pressure will shift east, allowing a mild
southwesterly flow to develop across the region Monday. A cooling
trend will begin on Tuesday and continue into Thursday before
high pressure returns for the end of the week.


.SHORT TERM (Through 12Z Wednesday)...Afternoon satellite imagery
and objective analysis show a mid level ridge remains centered
across the Desert Southwest, with the ridge axis building
northeastward across the eastern Great Basin. Mid level moisture
embedded near this ridge axis has allowed for limited cumulus
development across the higher terrain of southern Utah. Have
maintained slight chance PoPs across this area into the evening

An upper low spinning off the California coast is forecast to lift
northeastward into the Pacific Northwest/northern Great Basin
Monday through Monday night. As the ridge axis shifts east of the
forecast area, southwesterly flow aloft will overspread western
Utah allowing for a warming trend across the north, with KSLC
making a run at the 100 degree mark. Meanwhile the St George area
is expected to cool slightly, and given this have opted to allow
the going Excessive Heat Warning to expire this evening.

May see convection develop across northeast NV Monday afternoon
and spread into northwest Utah during the evening, which is hinted
at in the GFS, however many of the convective allowing models are
not developing convection Monday afternoon. Have maintained slight
chance PoPs for now across the northern third of the forecast area.

As this low evolves into an open wave while ejecting northeast,
the trailing surface front will cross northern Utah late Monday
night into Tuesday. This boundary is expected to cross the area as
a dry feature, but will knock 4-8 degrees off Max temperatures in
the north Tuesday, and 3-5 degrees in the south.

.LONG TERM (After 12Z Wednesday)....Weak waves will continue to
impact primarily northern Utah Wednesday into Thursday, keeping a
threat of convection over the higher terrain. This will also allow
temperatures to stay near to just slightly above seasonal normals.

EC/GFS then indicate high pressure building over the forecast area
Friday through the first part of the weekend, resulting in a drying
trend with a slight warming trend in temperatures. EC indicates some
modest cooling by day seven with the arrival of a Pacific storm
system, but the GFS keeps the trough onshore and keeps the ridge in
place through the end of the forecast period. Have introduced some
isolated POPs for next Sunday and lowered temperatures slightly to
account for the EC solution.


.AVIATION...The KSLC terminal will see VFR conditions through the
valid TAF period. Northwest winds will switch to southeast between
03-04z this evening.


.FIRE WEATHER...High pressure aloft remains centered across the
Desert Southwest this afternoon. Mid level moisture embedded
within this high will maintain a threat of isolated thunderstorms
across the southern mountains through this evening. This high is
forecast to move east Monday, allowing southwesterly flow to
overspread much of western Utah, resulting in Red Flag conditions
Monday afternoon across much of central and southwest Utah. In
addition, a warming trend is expected across the north while
conditions in the south remain hot and dry. There is also
a threat for isolated high based showers and thunderstorms
across northern Utah late Monday afternoon and Monday evening
with activity spreading out of northeast Nevada. Held off on
issuing a Fire Weather Watch given a high degree of uncertainty
regarding whether this convection will indeed develop and spread
into northwest Utah, as many convective allowing models remain dry
across this area Monday afternoon. A dry cold front is expected
to sweep through northern Utah Tuesday, followed by a dry westerly
flow for much of the remainder of the week.


UT...Red Flag Warning from noon to 10 PM MDT Monday for UTZ492-493-

     Excessive Heat Warning until 10 PM MDT this evening for UTZ019.




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