Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 231615

Area Forecast Discussion
National Weather Service Salt Lake City UT
1015 AM MDT Sat Sep 23 2017

.SYNOPSIS...An upper low over Nevada will slowly track across
Utah through the weekend, keeping cool and in some areas wet
weather in place. Another low may impact Utah midweek.


.DISCUSSION...A cool and somewhat moist easterly flow is under
cutting the moist southerly flow over Uinta County Wyoming this
morning and should prevail through the afternoon as the 700mb
baroclinic zones tightens up along the UT/WY border. Have added
patchy fog this morning and lowered the temps by several degrees
as sunshine is not expected at all today. Have also removed any
mention of showers for this morning as airmass rather stable.

The upper level closed low forming over Nevada will continue to
deepen a little more through today as energy seen on the WV
satellite imagery flows southward down the backside of this
elongated trough. This low will slowly migrate eastward into
southwest Utah this afternoon bringing a threat of isolated
thunderstorms. Elsewhere, do not see enough instability for
thunderstorms to occur with GFS Lifted Index values generally
above 0. Have therefore removed any threat of thunderstorms from
forecast across the rest of the CWA for today. The low level cold
air has pushed in across southwest Utah and with an extensive
cloud deck now and not expected to break as up slow flow remains
in place through the day, have lowered the temps there by 2-5

Sky cover was updated as well for mainly this morning with the
extensive stratus already in place across southwest Wyoming and
southwest Utah. Increased cloud cover for the Wasatch Mountain
valleys as the easterly flow aloft at 700mb upglides over the
cooler surface air. Perhaps there is an argument for sunnier
skies for eastern zones this morning but with cooling aloft this
afternoon the PC forecast looks on track.


.AVIATION...The current VFR conditions at slc terminal will begin
to deteriorate after 22Z. Ceiling around 4 kft will develop late
this afternoon/early evening. Periods of rain with ceilings near
2500 feet will develop between 03z-05z, then lower below 2000 feet
late tonight. Winds will be light west-northwest then increase
behind a cold front late this afternoon or early this evening.


UT...Winter Weather Advisory from 6 PM this evening to midnight MDT
     Sunday night for UTZ007.

     Winter Weather Advisory from 6 PM this evening to 4 PM MDT
     Sunday for UTZ517.




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