Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 211542

Area Forecast Discussion
National Weather Service Salt Lake City UT
942 AM MDT Sat Oct 21 2017

.SYNOPSIS...Cool and stable conditions will be in place today,
followed by significantly warmer temperatures Sunday. A weak
disturbance will bring cooler air back to the north Monday,
followed by a warming trend as high pressure aloft returns to the
region into midweek.


.DISCUSSION...Recent H5 analysis indicates a rapid building of
heights across the eastern Great Basin in wake of the most recent
trough passage. Increasing stability coupled with cool yet benign
conditions will be the norm across the area today, with only a net
increase of a mid/upper cloud deck across the north as
anticyclonic NW flow WAA impinges on the northern Rockies region
over the next 24 hours.

Not anticipating any precip of note within the WAA environment in
the short term, this as the core of the upper jet will remain well
north of the area. Current forecast remains on track and no
updates were made or are planned. Previous discussion below...

PREVIOUS DISCUSSION...Next storm system crosses the far northern
Rockies tomorrow night into Monday, allowing a shallow boundary
to slip south across the area. Again due to the jet position think
precipitation prospects are low. Could see locally gusty post
frontal winds across canyon/downslope areas of Southern Utah as
heights build Monday night.

Broad ridging will remain in place across the Southwest at the
start of the long term forecast period. A developmental trough
will approach the Pacific Northwest coast Wednesday morning. At
the same time, the upper level ridge will flatten and retrograde
west. This will allow the trough to continue to dig into the West
Thursday rather than previous model depictions of a splitting,
weakening system.

Timing of the associated frontal passage varies between the global
models and ensembles, but at this point much of the guidance points
to a fairly strong cold front crossing the state Thursday with the
potential for jet support/orographic upglide to enhance
precipitation near and behind the cold front. The GFS solution is
more of glancing blow to the state, whereas the EC solution is much
deeper and colder. Main change to the forecast at this time was to
trend slightly later in the day Thursday with the development of
precipitation. If run to run consistency continues, pops will need
to continue to be increased in later packages.

In the wake of the Thursday trough, ridging rebounds across the
Interior West, though the area remains under north to northwesterly
flow, limiting any potential warming.


.AVIATION...Operational weather concerns will remain minimal at
the KSLC terminal through the valid TAF period. Light and variable
winds currently in place are expected to become a prevailing
northwesterly between 17-18z. Northwesterly winds will remain in
place through the remainder of the day before returning to the
southeast around 04z this eve per norm.





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