Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 192126

Area Forecast Discussion
National Weather Service Salt Lake City UT
326 PM MDT Mon Jun 19 2017

.SYNOPSIS...High pressure will remain in place across the Great
Basin into Wednesday, bringing very hot temperatures to the
region. A series of dry cold fronts will start a gradual cooling
trend after Wednesday, primarily for northern portions of the
forecast area.


.SHORT TERM (Through 06Z Friday)...Strong high pressure is over the
forecast area this afternoon, resulting in hot and dry conditions
with light winds. Skies are clear with the exception of a bit of
cumulus buildup over the mountains of southern Utah, and PW values
are noticeably drier than yesterday, in the 0.3 to 0.5 inch range
across most of Utah and southwest Wyoming. Maxes today are
running 5-7F warmer than yesterday, which is 10-15F above climo.
Southern Utah is seeing the largest departures from climatology,
resulting in areas of dangerously warm temperatures. Going heat
headlines cover the threat well. Have already broken the maximum
temperature record for the day at Bryce Canyon, and could break or
tie a few more before the day is over.

The airmass will continue to warm tomorrow, with maxes running in
excess of 15F above seasonal normals across the area, so expect
more high temperature records will be broken. A bit of shortwave
energy moving into the ridge will also add enough instability to
combine with the very warm temperatures to result in a few high
based thunderstorms over the higher terrain.

The ridge is still on track to flatten beginning Wednesday in
response to a trough moving east along the US/Canada border. This
system will stay north of the area but will get close enough to
push a mostly dry cold front into the area beginning Thursday.
EC/GFS are now looking fairly similar through Thursday, pushing
the front into central Utah by Thursday afternoon. As a result,
temperatures should cool by around 10F compared to Wednesday`s
forecast maxes while the extreme heat continues over southern


.LONG TERM (After 06Z Friday)...Persistent and typical mid to late
June pattern continues through the long term portion of the
forecast. While mean ridging will be in place, several disturbances
will cross the northern Intermountain Region and may provide a few
chances for precipitation across mainly the higher terrain. Little
chance for precipitation for the lower elevations is expected
through the extended forecast period.

Enhanced mid-level moisture associated with a cold front will move
across central and southern Utah Thursday night may bring the threat
of a few high based showers/thunderstorms overnight. Behind this
boundary, "cold" air advection will bring 700mb temperatures down to
near 9-10C across northern Utah by Friday evening, bringing highs
back to the mid to upper 80s Saturday. It`s possible that Friday may
be a bit cooler than currently forecast.

Mean ridging will continue into early next week. A weak disturbance
riding the top of the ridge may bring the threat of precipitation to
Utah Monday into Tuesday but antecedent conditions preclude much of
a threat of measurable precipitation outside the higher terrain.


.AVIATION...The SLC terminal will see VFR conditions through the
evening with clear skies. Northwest winds are expected to shift to
the southeast between 03Z and 05Z.


.FIRE WEATHER...High pressure will remain the dominant feature over the
fire district through the middle of the week resulting in hot and
dry conditions with light winds. The extreme heat will result in
a Haines index of six for southern Utah through the work week.
Some weak instability will move into the ridge beginning tomorrow,
bringing isolated high based thunderstorms to the higher terrain
that have the potential to produce gusty and/or erratic winds. The
ridge will flatten Wednesday ahead of a cold front that will move
through the fire district beginning Thursday. The approach of the
cold front will increase winds over southern and eastern Utah out
ahead of it, so there is a possibility of red flag conditions for
those locations Thursday into Friday. The front will bring cooler
temperatures to northern Utah by Friday, with the cooler air
expected to move into southern Utah over the weekend.


UT...Heat Advisory until 10 PM MDT Thursday for UTZ013-020.

     Excessive Heat Warning until 10 PM MDT Thursday for UTZ019-021.




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