Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 241055

Area Forecast Discussion
National Weather Service Salt Lake City UT
355 AM MST Fri Nov 24 2017

.SYNOPSIS...A fast moving but weak weather disturbance will cross
northern Utah this afternoon. Strong high pressure aloft will
return this weekend, followed by a storm system early next week.


.SHORT TERM (Until 00z Tuesday)...A fast-moving shortwave
currently over southeast Oregon will move across northern
Utah/southwest Wyoming by early this afternoon. This feature does
appear that it will have fairly good baroclinic structure as it
moves through the area. Sufficient ambient moisture (PWAT values
0.50"-0.60"), decent low-level cold advection, dynamic lift from
the passing shortwave and the potential support for deep lift
from the overhead jet all point towards a short period of organized
precip across far northern Utah/southwest Wyoming during the

Building heights to the west in the wake of this shortwave will
lead to an increasingly anti-cyclonic flow aloft and an end to
any lingering showers early in the evening. A trailing secondary
shortwave late tonight/early Saturday should remain just north of
the state. Not anticipating any precip with this second feature,
though clouds may increase a bit through early Saturday.

A strong ridge of high pressure aloft will develop across the
interior west this weekend. This ridge will lead to dry
conditions and a continuation of unseasonably warm temperatures
Saturday. The axis of the upper ridge will shift just to the east
of Utah Sunday. This shift will result in an increase in southwest
flow aloft which will translate into breezy conditions and still
warmer temps for mainly western Utah Sunday.

The next Pacific trough will reach the west coast Sunday night.
Substantial differences exist in the global models concerning the
timing and intensity of this features as it advances into the
Great Basin. The latest run of the GFS remains a bit of an outlier
as it maintains a consolidated trough which arrives over Utah
Monday. The Canadian and ECMWF in contrast show a more pronounced
split to the trough well to the west. This splitting of the trough
will slow down the eastward progression and concentrate more
energy across southern Utah beyond the current short term forecast
period. At this time will follow the slower solutions of the
ECMWF and Canadian which would lead to limited convective precip
during the day Monday.

.LONG TERM (After 00Z Tuesday)...As the upper low progresses
southeastward Tuesday, the flow aloft turns northerly with the 700mb
baroclinic zone sagging southward through Utah and becoming more
disorganized. Quite a change in the extended forecast models from 24
hours ago to the current view, advertising a warmer and quicker
storm system for next week. As the flow shifts more northerly behind
the front, and a warmer, less frontogenetic system, a less favorable
snow event looks possible.

It was good to see the models come into somewhat better agreement as
of late with the Mon/Tues system. With the drastic flip-flop
solutions, most notably the GFS, confidence is still on the lower
side with regards on exactly how this will play out. Leaned heavier
on the ECMWF solution with regards to timing and snow levels

With shortwave ridging/zonal flow building in behind the departing
trough, both the GFS and EC (00z version) are advertising a weak
shortwave trough to drop south through mostly the northeast portion
of Utah late Wednesday. This system appears to be colder than the
previous one, and is consistent among extended models (700mb temps -
10C to -12C). Limited moisture is being advertised with this one
even with a better northwest flow regiment. Will have to continue to
monitor this as it develops further.


.AVIATION...Conditions at the KSLC terminal will be VFR through
the valid TAF period. Winds varying from northwest to southeast
overnight should settle in from the northwest by 16z - 17z. Ceilings
are expected to remain above 7000 feet during the day. A wind shift
to the southeast is expected by 03z.





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