Scientific Forecaster Discussion
fxus65 kslc 231049
Area forecast discussion
National Weather Service Salt Lake City Utah
349 am MST Thu Nov 23 2017
Synopsis...high pressure aloft across the region today will
weaken as a weather disturbance moves east across the northern
rockies tonight. Strong high pressure aloft will return this
weekend, followed by a colder storm system early next week.
Short term (until 00z monday)...the dominant upper ridge across
the region will bring another day of exceptionally warm
temperatures to Utah. Readings this afternoon will hover around
record levels, with more than a few new records expected today.
The weakening upper trough over the eastern Gulf of Alaska will
eject the remnant of this feature east across the northern rockies
tonight/early Friday. The associated low-level baroclinic zone
will settle into and then stall across far northern Utah late
tonight or early Friday.
The moisture plume extending from the tropical central Pacific
northeast into the northern California coast will inject some
moisture into the region ahead of the above mentioned upper
trough. This moisture, though interacting with weak dynamic and
thermally driven lift, will lead to generally light precip focused
along and north of the stalled baroclinic zone. Will nudge pops
up a bit across the far northern zones owing to the source of the
tropical source of the moisture and the location of the stalled
Suspect that the best chance for precip will come Friday morning,
then diminish fairly quickly as heights begin to build and the
flow turns more anti-cyclonic Friday afternoon/evening. Strong
high pressure aloft will center across Utah again on Saturday,
then shift east with an increasingly strong and warm southwest
flow developing Sunday. Anticipating good mixing Sunday, with
temps returning to levels much above normal for late November.
Long term (after 00z monday)...extended models differ in timing for
the trough progressing through the Great Basin Monday by at least 12
hours. With the most recent runs (06z GFS and 00z ec) the GFS once
again has shifted slightly slower and slightly more south. This
being said, confidence remains low with the progression of this
system. Pre-frontal winds Monday still looks to be on the stronger
side across the western half of Utah, as well as gusty northwest
winds behind the front. Made some upward adjustments however minor.
Among the global extended models the cold air associated with the
front seems coincident with the available moisture across northern
Utah. As snow levels plummet Monday (depending on the frontal
passage timing), some valley locations could see snow showers while
the mountains should see a decent snow accumulation. As the flow
shifts to northwest, the baroclinic zone becomes convergent along
the Wasatch front and southward through the central spine through
the south-central mountains. Again, timing has been inconsistent as
well as the track of the system, so confidence remains low in fine
Behind this front, high pressure looks to build in from the west
through the extended period of the forecast. Daytime temperatures
are trending cool to start the week with a gradual rebound upward.
Aviation...the slc terminal is expected to see southeasterly winds
persist until a switch to the northwest between 19z and 21z.
Increasing high clouds through the day should remain above 10000
feet above ground level.
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