Scientific Forecaster Discussion
fxus65 kslc 162233
Area forecast discussion
National Weather Service Salt Lake City Utah
433 PM MDT Mon Sep 16 2019
Synopsis...a strong cold front will sweep southeast across the
northern Utah this evening, then weaken as it moves into southern
Utah late tonight through Tuesday. Much cooler temperatures will
trail the cold front, followed by a brief warmup midweek ahead of
the next storm system arriving late in the week.
Short term (until 00z friday)...the upper trough with an embedded
vorticity Max along the Oregon/California border will continue
east and gradually weaken as it crosses the Great Basin through
early Tuesday. The associated surface front will remain fairly
strong as it moves out of Nevada and into northwest Utah this
evening. This front will weaken as it work into central/southern
Utah later tonight.
The main issue tonight will be the wind associated with the cold
front. This cold front supported by the fairly strong near 700mb
southwest winds has generated strong southerly winds across much
of western Utah this afternoon. These winds in the pre-frontal
environment will remain elevated early this evening, then switch
to the west and remain elevated across far northwest Utah trough
late evening. Persistent low-level cold advection will keep winds
elevated across the far north overnight. Lack of thermal support
farther to the south will result in decreasing winds behind the
front through central/southern Utah after midnight.
Convective precip looks to remain limited in intensity and areal
coverage as the aforementioned vorticity Max tracks east through
the western/northern Great Basin through early Tuesday. In Utah
the best chance for convection will come behind the surface front
and will concentrated near the vorticity Max embedded in the mid-
level cold pool along the Utah/Idaho border.
A dry/stable air mass and much cooler temperatures trailing the
cold front will bring fall-like conditions to the area Tuesday.
A new and colder upper trough advancing south along the britcol
coast will settle into the Pacific northwest by early Wednesday.
Backing flow across the Great Basin ahead of this feature will
bring warmer and windier conditions back into Utah Wednesday.
The cold front associated with this second trough will reach
far northwest Utah late Wednesday, then slowly work east as the
upper trough advances through the western Great Basin/northern
rockies through Thursday.
Areas east of this surface boundary will remain windy and warm
through Thursday afternoon. Behind the front much cooler
temperatures will return, with precip remaining close to the
strongest lift and cold air aloft with the trough over northwest
Utah and points north and west.
Long term (after 00z friday)...the deepening positively tilted
trough swings through the Great Basin late Thursday into Friday
brining another round of gusty pre-frontal winds and precipitation
along with colder temperatures. This system digs a bit farther south
than the previous one and has some colder air associated with it.
The frontal passage looks to be late day/evening timing, similar to
this past trough passage, but should have some weaker winds behind
As the cold core moves over northern Utah Friday the best energy
will be lined up with precipitation timing. This could result in
showery conditions across northern Utah Friday morning through
afternoon. Models, both deterministic and ensembles have a good
handle on this system and are thankfully all in agreement with one
another largely. Some variances over the last few runs, but overall
the trend is coming together much better. As the weather system
lifts to the northeast by Saturday, rising heights and warming
temperatures will slowly build back in from the west.
Aviation...southerly winds will continue to increase through the
morning at the slc terminal. Wind gusts are expected to near to
exceed 35kts after 19z. A strong cold front will cross the terminal
between 03-06z tonight...bringing a significant wind shift to the
Fire weather...the upper trough over the West Coast states late
the afternoon will weaken as it moves east across Utah later
tonight through early Tuesday. The associated cold front will
remain strong as it enters Utah this evening, with strong
southerly winds ahead of the front and gusty northwest winds
behind the front this evening. Much cooler temperatures will
follow the front for Tuesday.
The next storm system will move into the Pacific northwest by
early Wednesday, then work slowly east across the northern
rockies and Great Basin late in the week. Windy and warm
conditions will develop ahead of this storm Wednesday and
Thursday, with precipitation and cooler air moving into the
state by late Thursday and Friday.
Utah...red flag warning until 4 am MDT Tuesday for utz478-482-489-
Wind Advisory until 4 am MDT Tuesday for utz001>004-006-014>016-
High Wind Warning until 4 am MDT Tuesday for utz005.
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