Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 200406

Area Forecast Discussion
National Weather Service Salt Lake City UT
1006 PM MDT Thu Oct 19 2017

.SYNOPSIS...A rather cold storm system entering the Pacific
Northwest tonight will sweep east across the Great Basin Friday
through Friday evening. A strong cold front will bring
substantially cold temperatures to Utah through the first half
of the weekend.


.SHORT TERM (Until 12z Sunday)...The cold core upper level trough
along the Pacific Northwest coast this evening will continue
inland overnight, then track east across the northern
Rockies/northern Great Basin Friday. The associated surface cold
front will continue strengthen overnight/early Friday as the
supporting low level cold advection increases ahead of the
approaching upper trough.

The front should reach far northwest Utah early Friday morning,
then surge east across the state during the day. Southerly winds
will increase overnight with support from near 700mb southwest
winds between 40-50 knot winds. Not anticipating much in the way
of precip along the frontal boundary as it outruns the dynamic
lift and mid-level cold from the upper trough. The best chance at
precip will arrive with the main trough, though even then this
precip will be confined mainly to the north closer to the colder
air and best dynamic lift.

Temperatures beginning Friday will turn much colder behind the
front as near 700mb temps drop 13-16 degrees Celsius from this
evening through Friday night. Temperatures will remain below
normal through Saturday night.

.PREVIOUS LONG TERM (After 12z Sunday)...The warm front at the
nose of the short wave ridge building into the Great Basin will be
moving out of nrn UT Sun morning. Clouds across the north will be
dissipating and the airmass warming during the day with surface
temps responding well due to a well mixed airmass. Models now
produce a little qpf for the far nrn mtns Sun morning and added
some low pops for this area.

The ridge remains centered to our west thru Mon with another weak
flat wave on the nw flow bringing clouds and wind to the nrn CWA
Sun night into Mon. Do not expect any precip from this but it should
prevent valley inversions from developing and expect highs Mon to
be quite mild once again.

The strong upper ridge moves overhead Mon night thru Tue night
with a very mild airmass aloft. Increasing inversions however may
result in temps not warming much more in the nrn and ern valleys.

The guidance agrees that the ridge retreats west somewhat Wed into
Thu as a low amplitude but vigorous short wave trof clips the nrn
CWA. Do not expect precip from this feature either but once again
it should bring some cloudiness, and increase in winds, and
cooling aloft to the area.


.AVIATION...The developing cold front still well to the west of
Utah this evening will reach far northwest Utah early Friday.
Gusty southerly winds will advance to the terminal midnight, then
gradually increasing through the balance of the overnight hours.

Southerly winds will peak Friday morning before shifting to the
west-northwest with the passage of the cold front between 17z and
19z. Ceilings will lower along and behind the front, dropping to
around 4 kft in precip around 20z





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