Area Forecast Discussion
Issued by NWS Salt Lake City, UT
FXUS65 KSLC 191046
Area Forecast Discussion
National Weather Service Salt Lake City UT
446 AM MDT TUE JUL 19 2016
.SYNOPSIS...High pressure over the southern plains with an upper
level trough along the Pacific Northwest coast will leave the
Great Basin under a southwest flow through much of the week, with
moisture remaining over southern and eastern Utah.
.SHORT TERM (Through 06Z Friday)...A mid level ridge centered
across the southern Plains coupled with an upper low spinning
along the Pacific Northwest coast is inducing a deep layer
southwesterly flow across the Great Basin region this morning.
Moisture within this flow which advected northward across the
forecast area Monday remains in place across the east, while drier
mid level air noted in water vapor imagery has advected into
western UT. This has resulted in a notable decrease in GOES
derived precipitable water values across western and central Ut.
Despite the lingering moisture only meager instability is expected
to develop today owing to marginal mid level lapse rates and
moisture remaining largely confined to the mid levels with a very
deeply mixed sub cloud layer. As such have trimmed POPs across
the eastern valleys back into the isolated range, with a bit
better coverage along the terrain. With drier air, southerly flow,
and deep mixing across western UT will see a slight uptick in max
temps today with KSLC making a run at the 100 degree mark.
Not much change in the overall pattern is expected throughout the
short term period, with moisture perhaps increasing just a bit and
expanding a bit north and westward, but convection remaining
largely limited by meager instability. Have maintained the
highest POPs east of I-15 while the west largely remains dry
through the forecast period. Temperatures will fluctuate little
from day to day with KSLC flirting with the 100 degree mark each
afternoon through Thursday.
.LONG TERM (After 06Z Friday)...The mean ridge dominating the
southwestern CONUS will continue to build west into Friday as the
previously persistent upstream trough over the PacNW continues to
split with remnant energy retrograding west towards 140W.
Resultant flow aloft locally will trend more west-northwest aloft
allowing a drier airmass to spread across the eastern Great Basin
beginning late week as a result. Have maintained isolated coverage
of convection over the central mtn spines over central/eastern
Utah due to evacuation of holdover low level moisture from
previous days, though as a whole the area will transition into a
drying trend into and through the weekend.
Bottom line outside of this isolated convection potential on
Friday, the area will trend drier and remain above seasonal
regarding temps as the influence of the high will promote modest
subsidence driving surface temps some 5+ degrees above climo into
early next week.
.AVIATION...Southerly surface winds are expected to become
increasingly gusty after 15/16z this morning at the KSLC terminal.
With this said, a 30 percent chance exists that gusts exceeding 30
mph will occur in the 16-20z window. A 40 percent chance exists
that the lake breeze will attempt to shift winds to the northwest
between 21-23z this afternoon, though it remains possible that
this boundary will only push part way across the terminal if it
advances at all.
.FIRE WEATHER...Moisture which has worked its way northward
across southern and eastern Utah will remain in place today
allowing for elevated humidity values. despite this moisture the
airmass will remain quite stable with only isolated to widely
scattered thunderstorm coverage this afternoon and evening.
Meanwhile drier air will reside across western Utah. Little
change is expected through Wednesday before the airmass dries out
late in the week through the upcoming weekend.
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