Scientific Forecaster Discussion
fxus65 kslc 250451
Area forecast discussion
National Weather Service Salt Lake City Utah
330 PM MDT Mon Jul 24 2017
Synopsis...monsoonal moisture spreading north across the Great
Basin will maintain widespread precipitation across Utah through
midweek. A gradual drying trend is expected for the latter portion
of the week.
Short term (tonight through 12z wednesday)...the monsoonal surge
which began earlier today should cover the entire forecast area by
late tonight. Across southern Utah the convection that generated
some heavy rainfall has turned more stratiform and somewhat less
intense this evening. This break will be short-lived as the
shortwave lifting north through Arizona advances into southwest Utah
later tonight. Already beginning to see an increase in convection
with significant cloud top cooling noted with the storms entering
extreme southwest Utah late this evening.
Increasing dynamic lift from the advancing shortwave into a
conditionally unstable air mass across southern/central Utah should
easily generate another round of widespread and occasionally heavy
rains later tonight through Tuesday. Will maintain the current Flash
Flood Watch as configured, with the best threat for flooding
returning late tonight through Tuesday morning, then one final push
late Tuesday afternoon through mid-evening.
Up north a second shortwave lifting east-northeast out of Nevada is
creating a steadily expanding area of convection late this evening.
This activity will continue throughout the night, then decrease
rapidly behind the shortwave as it exits the area Tuesday morning.
Dynamic subsidence may hold convection back much Tuesday afternoon,
then break through again late Tuesday afternoon as a second
shortwave moves through during the late afternoon through overnight
Previous long term (after 00z thursday)...a shortwave trough moving
through Nevada into southeast Idaho Thursday will usher in drier mid to
upper level air in Utah. Low level moisture will continue to linger
throughout much of Utah, with precipitable water values ranging between 0.8-1.0"
across the state. Thus, expect isolated to scattered thunderstorms
across much of Utah Thursday afternoon, with the best coverage over
and near the higher terrain. Central and northern Utah will continue
to dry out Friday, as dry air continues to stream in from the west.
The upper level ridge will shift over the four corner region Friday
afternoon, with an uptick in mid to upper level moisture expected to
wrap around the ridge and into southern Utah Friday afternoon,
allowing for isolated to scattered convection to develop across the
higher terrain of southern Utah.
High temperatures will be on the increase Saturday afternoon as the
ridge shifts across east-central Utah. High temperatures will run
about 5f above normal state-wide with temperatures approaching the
century mark across the Wasatch front. Isolated to scattered
convection will once again develop across southern Utah's higher
terrain Saturday, where mid to upper level moisture continues to
hang around, while northern and central Utah remain dry.
With minimal change to the mean ridge position through day 7,
maintained convective potential through the end of the forecast
period (pops trended towards climo a bit), while maintaining above
climo temps both night/day.
Aviation...the shortwave moving east-northeast out of Nevada will
generate showers and a few thunderstorms for the terminal area
overnight. Brief MVFR conditions in heavier rains are possible.
Gusty winds will accompany thunderstorms, though speeds will
generally ream in at or below 30 kts. Showers and Stroms will likely
end early Tuesday morning, then reform again during the late
afternoon and evening hours Tuesday.
Utah...Flash Flood Watch through Tuesday evening for utz010-012>016-
For more information from noaa's National Weather Service visit...