Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 242122

Area Forecast Discussion
National Weather Service Salt Lake City UT
322 PM MDT Mon Oct 24 2016

.SYNOPSIS...A moist southwest flow over the Great Basin will
persist into Tuesday. A couple of weather disturbances embedded
within the southwest flow will generate widespread precipitation
across the region through early Tuesday. A gradual warming and
drying trend will begin midweek as high pressure aloft strengthens
across the Great Basin.


.SHORT TERM (Through 00z Friday)...
Water vapor loop shows southwest flow aloft between a cold closed
low over off the Pacific Northwest coast and a strong ridge over
Texas. MDCARS wind observations show a 100-145kt cyclonic jet into
the Pacific Northwest and northern Rockies. GOES/HRRR/12Z KSLC
RAOB indicate the precipitable water value ranges from 0.25"-0.50"
mountains to 0.65"-0.85" western and southern valleys.

The arrival of the moisture plume will continue to support
destabilization as the day progresses. Meanwhile, diffluence
aloft along with jet coupling will continue to support an increase
in storm coverage through the day.

Simulated reflectivity from the HRRR and NCEP/local WRF models
suggests that organized convection may occur. SREF indicates a
good chance of seeing 40kts of effective shear later this
afternoon. Will have to monitor for a locally heavy rainfall
threat as well as the threat of a few stronger storms. Snow
Levels look to be around 10ft.

A strong Pacific jet nosing into California will reach far
western Utah by morning. This encourages an upper level trough to
cross overhead in advance of this feature tonight. Expecting this
feature to shunt the active weather to the east as the night
progresses. This results in some drying as heights rise to the

Showers will be more isolated to scattered in nature tomorrow
across the north, supported by the left exit region of the
aforementioned jet.

The pattern amplifies Wednesday and Thursday leading to warming
temperatures. Cant rule periods of high clouds with the
combination of Pacific moisture aloft, in proximity to the
weakening jet.

.LONG TERM (After 00z Friday)...
Long wave trough position will remain over the eastern Pacific
through the early portion of the extended but then shift inland
and weaken by early next week. With the trough off the coast
moisture from a sub tropical system currently off the southern
coast of Mexico is expected to be tapped and brought northward by
a short wave rounding the base of the trough on Friday. Although
the dynamics are not the greatest on Friday the fact that there is
sub tropical moisture readily available have increased the PoPs to
slightly above the highest model guidance at this time which
probably is not high enough. Just wanted to start the trend upward
for now.

The GFS keeps a fair amount of moisture around into Saturday but
believe that there is enough subsidence behind the Friday short wave
and ahead of the long wave trough that only isolated showers are
expected in the mountains. The GFS appears to be generating too much
QPF so leaned toward the drier EC solution.

South winds increase on Sunday ahead of the well defined short wave
at the leading edge of the long wave trough moving across Nevada.
The GFS model runs have been trending towards this more progressive
and consolidated trough moving into Utah Sunday night into Monday
over the pass 4 model runs. This is also supported by EC ensemble
mean of the 00Z run so confidence fairly high that a cold front will
move through the CWA with the brunt of the weather across the north.
As a result, have boosted PoPs and lowered temperatures Sunday night
and Monday. Lowered snow levels as well down to near 6500-7000 ft
MSL by Monday morning.


Southerly winds gusting over 25 knots will persist at KSLC until
22-23Z. Southerly winds will remain strong through the night but
gusts will generally be less than 25 kts. After 23-01Z there will
be an increased threat of showers impacting the terminal. These
showers will likely bring periods of erratic winds and lowered




SHORT TERM...Rogowski
LONG TERM...Sturthwolf

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