Wednesday, May 24, 2017, 4:19 AM EDT
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Area Forecast Discussion
Valid At
Wed, Dec 31, 7:00pm EST
FXUS65 KSLC 240339

Area Forecast Discussion
National Weather Service Salt Lake City UT
939 PM MDT Tue May 23 2017

.SYNOPSIS...High pressure aloft will shift east of the region 
early Wednesday. This exiting high pressure will be followed by
a series of weather disturbances which will impact Utah late 
Wednesday through the first half of the upcoming weekend.


.SHORT TERM (Through 12Z Friday)...The axis of the upper ridge
entering western Utah at mid-evening will continue east across 
the state overnight ahead of the upper low advancing southeast
along the Britcol coast. This low will take a turn to the east,
tracking across southern Canada through the end of the week.

A series of vorticity lobes will rotate south along the back side
of the upper low, with each of these reaching northern Utah at 
some point through early Saturday. The first of these features
will drive a fairly strong baroclinic zone south across the 
northern half of Utah Wednesday night. Moisture drawn in ahead of
this feature California could fire up isolated convection late
Wednesday, with this convection increasing along the baroclinic
zone the northern third of Utah and southwest Wyoming. Mid-level
dynamic support for lift will likely shear off to the east as the
thermal boundary settles into central Utah and weakens. Could
still see some loosely organized showers along the boundary,
though the trend on areal coverage and intensity should be
decreasing heading into Thursday.

Subsequent vorticity lobes rotating south into Utah will bring
additional cool air south with convective precip increasing along
these dynamic features. Temps will be somewhat cooler heading into
the end of the week. Precip types should remain as rain at all
elevations through Thursday night, though can not rule out a
little snow mixing with the rain at the highest elevations of the

.PREVIOUS LONG TERM (After 12Z Friday)...Global models remain in 
good big picture agreement regarding evolution of the northern 
Rockies long wave trough, and the associated short wave energy 
rotating through it late week. With the remnant cold front stalled
over central Utah to begin the long term period, encroachment of 
the next short wave into northern Utah Friday will tighten thermal
packing across northern/central Utah providing a focus for 
scattered convection by midday. Vertical profiles in BUFRS suggest
the bulk of convection will need to be forced due to limited 
instability, so anticipate showers/storms to largely remain 
confined to the frontal zone, gradually shifting south/east into 
Friday night as the short wave sags into central Utah overnight. 
Made subtle changes to PoPs, namely continuing a slight increasing
trend across Castle County Friday night due to the anticipated 
forcing in place at that time.

Downstream progression of the short wave and attendant cold front 
Saturday will limit additional convective potential, but have 
maintained slight chance PoPs over the terrain due to remnant low 
level moisture supporting an opportunity for shallow convection to 
form over the mtns.

Beginning Sunday a transition period will begin with encroachment of 
a mid level ridge building in from the west. Globals continue to 
portray a notable warming trend beginning Sunday and lasting through 
the end of the long term period within an increasingly stable 
environment as such. Temps by midweek will most likely be pushing 10 
or more degrees above climo as a negatively tilted ridge axis 
positions overhead. 


.AVIATION...High pressure aloft moving east across Utah tonight
will maintain VFR conditions at the terminal until late in the
current TAF period. Light southeast winds will become more
southerly and increase ahead of a cold front advancing on Utah
from the north Wednesday. This front will reach the terminal area
between 00z and 02z Wednesday evening. VFR conditions will
persist behind the front, though a few showers could develop over
or near the terminal.





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