Area Forecast Discussion
Issued by NWS Salt Lake City, UT
FXUS65 KSLC 270853
Area Forecast Discussion
National Weather Service Salt Lake City UT
253 AM MDT SAT AUG 27 2016
.SYNOPSIS...Moisture will remain in place over southern Utah
today. Drier air will gradually spread into the area from the
north over the weekend and into early next week.
.SHORT TERM (THROUGH 06Z TUESDAY)...
Water vapor loop shows a shortwave trough nearing southwest Utah.
MDCARS wind observations show a 50-80kt cyclonic jet from northern
Nevada into southern California into southwest Utah. GOES/HRRR/00Z
KSLC RAOB indicate the precipitable water value ranges from
0.15"-0.25" northern mountains to 0.75"-1.00" southern valleys.
Starting out this morning with copious cloud cover across the
south as convection begins to diminish in intensity. Convection
should focus into Arizona this morning as the wave continues to
dig further to the southeast.
Questions remain regarding developing enough widespread
instability for deep convection this afternoon due to the
convective debris. Models certainly do so with slow storm motions.
However, the warm cloud layer is quite shallow. Dewpoints at or
above 50F along the Arizona border. So will hold off on a flash
flood watch but do have Moderate Flash Flood Potential across the
eastern parks where dynamic lift could compensate for the slow
destabilization process today.
With some dynamical lift and remnant instability aloft kept low
PoPs in for southern Utah tonight. Sunday and especially Monday
convection should become more diurnal in nature and tied to the
higher terrain as anticyclonic flow develops aloft. This will
support a warming and drying trend across the region.
.LONG TERM (AFTER 06Z TUESDAY)...
Ridging will be in place to start the long term forecast period.
An upper level trough will approach the Pacific Coast early
Tuesday gradually weakening as it crosses the northern Sierras.
Ahead of this trough, moisture will begin to be pulled northward,
first into southeastern Utah Wednesday gradually pushing into
central and northern Utah later Wednesday into Thursday. Much of the
global model guidance has moved toward a slower moisture surge.
Given the model to model and run to run consistency issues, did not
want to be too aggressive with adjusting pops toward the 00Z runs.
Current forecast may contain pops that are too high Tuesday and
Temperatures are expected to remain above normal through Friday as
summer is slow to end at the start of meteorological fall.
Southerly winds at the SLC terminal are expected to shift to the
northwest between 19-20Z.
Yesterday`s ERC values were at or above the 90th percentile
across much of northern Utah, while stations across southern Utah
remain below the 50th percentile.
Convection will be limited to mainly southern Utah today, then
more diurnal and terrain based Sunday and Monday. A warming and
drying trend will prevail into mid week.
A monsoon push will increase the coverage of thunderstorms mid to
late next week, supporting a gradual cooling and moistening trend
and another round of lightning.
SHORT TERM/FIRE WEATHER...Rogowski
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