Scientific Forecaster Discussion
fxus65 kslc 181616
Area forecast discussion
National Weather Service Salt Lake City Utah
1016 am MDT Wed Sep 18 2019
Synopsis...warmer temperatures and increasing southerly winds
are expected today ahead of the next storm system approaching Utah
from the Pacific northwest. This storm will move through the area
late Thursday through Friday, bringing cooler temperatures and an
expanding area of precipitation. Drier conditions will follow for
Discussion...the cold core upper trough currently positioned
along the Pacific northwest coast will continue on a slow eastward
track across the Great Basin/northern rockies through Friday.
Southwest flow aloft downstream from this trough along with the
strengthening cold front advancing east across Nevada will result
in warmer and windy conditions across much of the western and
northern portions of the forecast area this afternoon. Much
cooler temperatures along with an expanding area of precipitation
will press into mainly northern/central Utah and southwest
Wyoming with the trough passage late Thursday/Friday.
The surface cold front, based on satellite imagery, has likely
moved into extreme northwest Nevada/eastern Oregon this morning.
The thermal gradient defining this frontal boundary should tighten
as it crosses northern Nevada this afternoon. Convection
associated with this feature will likely concentrate along the
trailing near 700mb baroclinic zone. The early afternoon
convection will be weak and somewhat isolated in coverage as
convergence into the low-level boundary will be minimal, moisture
limited, and the mid-level cold air will be lagging back to the
west with the main trough.
Anticipating an increase in intensity and areal coverage of
convection later in the afternoon as low-level convergence
increases with increasing moisture/instability as the mid-level
trough and associated cold air aloft advance across northern
Nevada. Increasing jet support rounding the base of the trough
will also add the upper divergence component to the mix to
support stronger, organized convection.
Convection in Utah will likely be limited to the far northwest
corner late this afternoon and evening. Convection will gradually
expand across northwest Utah along the advancing low-level
baroclinic zone, though strong convection would still lag back to
the west closer to the best dynamic/thermal forcing and upper jet
By late Thursday/Friday a broad area of synoptic-scale lift will
exist across the northern half of the forecast as the core of the
upper trough works east through the area. Widespread precip looks
to develop with this feature, with the areal extent likely greater
than indicated in the model guidance. The expected near 700mb
temps would suggest snow levels down to elevations close to the
higher valley locations of far northern Utah late Thursday night
through Friday morning.
No updates planned at this time.
Aviation...southerly winds are expected to become increasingly
gusty at the kslc terminal this afternoon, with a 60% chance of wind
gusts in excess of 30 mph developing after 18z. A cold front is
expected to cross the terminal between 10-12z Wednesday switching
winds to the northwest earlier than normal.
Utah...red flag warning until 10 PM MDT this evening for utz492.
Fire Weather Watch from Thursday morning through Thursday
evening for utz497-498.
Red flag warning until 10 PM MDT Thursday for utz495.
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