Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 272123

Area Forecast Discussion
National Weather Service Salt Lake City UT
323 PM MDT Tue Sep 27 2016

.SYNOPSIS...High pressure will break down and shift east tonight
as a weak storm system moving up from the south begins spreading
moisture back to the area. This moisture reaches northern Utah
by Wednesday evening and remains across the area into the weekend.


.SHORT TERM (Thru 00Z Friday)...Dry ridge conditions remain in
place across UT this afternoon with the high remaining centered
over nrn UT. A weak closed low is starting to lift out of Mexico
into swrn AZ and the associated moisture covers most of AZ.

The ridge over nrn UT is forecast to break down and shift east
over the next 24 hours allowing the low to start to open up and
move north with the associated moisture spreading into srn UT. The
moisture reaches nrn UT Wed eve.

Convective forcing will be weak on Wed due to weak dynamics with
the opening wave and shorter days resulting in less daytime
heating. The best chance of rain looks to be in close proximity
to the opening wave over srn UT Wed night and nrn UT Thu morning.

The opening wave leaves a remnant closed low behind off nrn Baja
as it lifts out to the northeast. This remnant low entrains
moisture from dying TS Roslyn and then it too then lifts newd
into AZ on Thu reaching sern UT during the aftn.

.LONG TERM (After 00Z Friday)...Active pattern setting up for the
long term portion of the forecast.  Upper level diffluence and
moderate mid-level moisture will aid in the continued threat of
precipitation across portions of eastern Utah Thursday evening into
Friday morning. An upper level trough digging off the Pacific Coast
will help to shunt this midlevel moisture east of the area by Friday
afternoon, though enough remnant moisture should remain to allow for
a few showers and possibly a thunderstorm across mainly the higher
terrain Friday afternoon and early evening.

The previously mentioned upper level trough will be the focus of the
weather Saturday through Tuesday. Several vorticity maximums will
rotate around this trough Saturday into Sunday into the Interior
West. This will help to provide sufficient lift for precipitation
across portions of northern and central Utah until the main trough
crosses the area.

Finally, a stronger wave will cause the trough to deepen and dig
southeastward, crossing the Great Basin later Sunday into Monday. As
this wave rounds the trough, the trough is expected to lift into the
northern Rockies Monday. Behind this trough, northwest flow is
expected to develop, likely with at least a few disturbances moving
through the area Tuesday through the Thursday.

Probably one of the more noticeable effects of this trough will be
below normal temperatures by Monday, with the Wasatch Front
struggling to get into the 60s after temperatures near 80 Saturday.


.AVIATION...Northwesterly winds at the KSLC terminal are expected
to switch to southeast between 03-04z.


.FIRE WEATHER...Moisture will start to spread into southern Utah
tonight as a weather system over southwestern Arizona begins to
lift north. This system will weaken as it lifts through the
district Wednesday night through Thursday but will bring a chance
of rain to many areas as it goes. RH will come up but clearing
indices will also rise as the airmass becomes more unstable.
Another system will bring a better chance of rain to southeastern
Utah Thursday afternoon into Friday morning.

The moisture from these systems is expected to linger over the
area Friday into Saturday keeping a threat of isolated showers and
thunderstorms going for most of the district.

A cold front approaching from the northwest on Saturday will kick
up the south winds across the district Saturday into Sunday.
Colder air will spread into the north late Sunday through Monday
bringing the snow levels down to around 6000 feet across the





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