Scientific Forecaster Discussion
fxus65 kslc 200345
Area forecast discussion
National Weather Service Salt Lake City Utah
945 PM MDT Tue Sep 19 2017
Synopsis...Wednesday will be a break between storm systems, and
then a cold upper trough will move into Utah starting Wednesday
night. This colder storm system will linger over the area through
the end of the week and into the upcoming weekend.
Discussion...the upper trough that brought precipitation and cooler
air to the forecast area last night and today is now heading towards
the northern Great Plains. The decaying cold front has made it past
a Milford to Green River line and is expected to make very little
additional forward progress. A cyclonic westerly flow aloft remains
in place currently, but will become a bit more zonal by late tonight
or early tomorrow morning as the pattern flattens. The cold airmass
and mostly clear skies will allow for much cooler overnight mins
compared to last night for areas behind the cold front.
A warmer southwesterly flow aloft will develop tomorrow in advance
of the next trough which will be carving into the Pacific northwest
region. The associated cold front will then sag into northwest Utah
by tomorrow evening, then slowly cross the rest of the forecast area
through Friday. This slow movement is due to the trough axis
remaining elongated upstream and then eventually pinching off into a
closed low while various vort lobes eject through the area. With the
cold front strengthening with increasing convergence into the
boundary, a band of precipitation is expected to develop, while the
front's slow-moving nature should allow for long duration of
precipitation which should result in relatively high amounts for
much of the northwestern half of Utah as well as southwest Wyoming.
Updated the forecast mainly to remove pops, reduce cloud cover, and
increase Eastern Valley winds for the rest of the evening.
Aviation...northerly winds will continue at the slc terminal
through 06-08z. Otherwise, expect VFR conditions with some clouds
well above 7000ft.
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