Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 122141

Area Forecast Discussion
National Weather Service Salt Lake City UT
341 PM MDT Mon Mar 12 2018

.SYNOPSIS...High pressure will build over the area through
Tuesday. A broad Pacific storm system will impact the region
beginning midweek.


.SHORT TERM (Through 00Z Friday)...High pressure firmly in place
over the region this afternoon with the axis just west of the
Utah/Nevada border. As a result, seeing mostly clear skies and
mild temperatures this afternoon across Utah and southwest
Wyoming, with maxes running around 10F above seasonal normals. The
ridge axis shifts just east of the area tomorrow as the airmass
continues to warm, so maxes tomorrow will approach record values
in some locations, especially across northern Utah.

The Pacific storm system currently centered near 135W will
continue tracking east over the next few days, reaching the
California coast on Wednesday. Ahead of this system, southerly
winds will pick up over the forecast area, especially over western
Utah where models are indicating 700mb flow of around 50 kts
Wednesday morning. The system is progged to split as it moves
onshore, with the first piece moving into the area along with the
associated cold front Wednesday afternoon through Wednesday night,
resulting in a period of precip.

EC/GFS continue to disagree on the details regarding this first
system, with the GFS showing it weakening significantly as it
moves through and keeping the associated precip primarily over
northern portions of the forecast area. The feature remains more
robust in the EC solution and is also broader, extending into
northern Arizona. As a result, the resultant precip and cooling of
temperatures extends more into southern Utah. Have favored the GFS
with this package as it has been more consistent, but have
extended chance POPs into southern Utah to account for the EC
solution. The associated cooldown will be undoubtedly significant,
moving maxes back to near or slightly below seasonal normals for
Thursday. All guidance keeps shortwave energy over at least
northern Utah through the end of the work week, so have maintained
some POPs through the short term period.

.LONG TERM (After 00Z Friday)...High confidence exists regarding
increasingly unsettled and cooler conditions across the area late
week and especially into the weekend. Specific evolution of the long
wave trough as it slowly translates inland and across the Great
Basin/northern Rockies region during this time remains much lower
confidence, though am beginning to see more things to key in on.
This especially holds true regarding the most likely period for the
parent trough crossing the area (either Saturday or Saturday night).

Differences continue to exist in globals regarding the amplitude and
specific timing of the above mentioned, so have opted to go with a
blend of ensemble mean progs with the operationals, and the majority
point to late Saturday and Saturday night being the most likely
period for the trough passage. With this, did focus highest PoPs for
the Saturday night period coincident with a gradual transition to
allow for that precip to transition to valley snow. Outside of this
bigger picture trend, limited skill exists to provide much in the
way of more detail at this time.


.AVIATION...VFR conditions will persist at the SLC terminal
through the evening with decreasing clouds. Northwest winds are
expected to switch to the southeast between 03z-04z.




SHORT TERM...Traphagan
LONG TERM...Merrill

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