Scientific Forecaster Discussion
fxus65 kslc 211034
Area forecast discussion
National Weather Service Salt Lake City Utah
334 am MST Tue Nov 21 2017
Synopsis...high pressure will strengthen across the region today,
and remain in place through the remainder of the week.
Short term (through 00z saturday)...an amplifying mid level
ridge extends across much of the Great Basin northward into the
Pacific northwest early this morning, while downstream a shortwave
trough and associated jet is noted digging through Wyoming. A
remnant moisture plume associated with this trough trails westward
into northern Utah, where isentropic ascent continues to fuel
bursts of precipitation. Much of this has been evaporating before
reaching the valley floors, with Logan sporadically reporting
light rainfall. As the upstream ridge axis continues to strengthen
and build eastward, anticipate any precip threat will continue to
wane, and have confined chance pops through the morning hours
across the higher terrain of northern Utah.
This ridge will become the dominant feature across the region
through Thanksgiving, and with a combination of overnight cloud
cover and warming temperatures aloft, weak valley inversions
should erode allowing for a warming trend across all areas through
Thanksgiving. A shortwave trough is forecast to crest the ridge
axis as it traverses the northern rockies Thursday night, pushing
a shallow frontal boundary through northern Utah Friday.
Anticipate only a slight cooldown across the north while the south
remains unaffected by this feature.
Long term (after 00z saturday)...the weekend starts off the
extended period under building and strengthening high pressure
across the Desert Southwest. Southwest flow aloft increases as the
weekend comes to an end and warm advection prevails over the
A shortwave trough begins to swing inland into northern
California Monday, as global models have come into better
alignment with this feature. Differences still reside among the
models, especially timing, however the track and location are
fairing better sync moving through the Great Basin. Increasing
southwest winds ahead of this feature Monday are being advertised
by models, and as such have increased winds across the west
deserts Monday. As the wave tracks east into Wyoming, cold air
aloft sinks southward bringing a rather weak baroclinic zone
through northern Utah. Some moisture associated with this feature,
and perhaps more behind the departing wave may give way to
showery conditions Tuesday into Wednesday. Speaking of cold air
aloft, snow levels look to lower to benches or valley levels
depending on the model guidance. Confidence in these details is
still very low with this being the far extended, but the pattern
is evolving this direction.
Aviation...mostly cloudy skies will prevail at the slc terminal
through mid-day today. Light southerly winds will shift to the
north by 18z when cigs should begin lifting above 7000 feet. A 30
percent chance that cigs remain at 7000 feet through 22z. A return
of the winds to the southeast is expected by 03z this evening.
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