Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 231157
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
457 AM MST Thu Jan 23 2020

.SYNOPSIS...High pressure aloft will shift east across the Great
Basin and bring more stable conditions to the area through
Thursday night. A fast-moving trough will impact northern Utah and
southwest Wyoming Friday, with high pressure aloft retuning for
the weekend.

&&

.SYNOPSIS...High pressure aloft will shift east across the Great
Basin and bring more stable conditions to the area through
tonight. A fast-moving trough will impact northern Utah and
southwest Wyoming Friday, with high pressure aloft retuning for
the weekend.

&&

.SHORT TERM (Through 00Z Sunday)...A mid level ridge encompasses
much of the Great Basin early this morning, with the associated
axis located near the crest of the Sierras. This is inducing a
mean northwest flow downstream across the forecast area, where
lingering moisture within this flow continues to allow for light
orographically forced precipitation along the Wasatch Range.
Further south lingering moisture across the eastern valleys
continues to result in areas of low stratus and fog. Both the
northern snowfall and the stratus/fog across the eastern valleys
should persist into the morning hours and have adjusted the near
term forecast accordingly.

The mid level ridge is forecast to weaken today into tonight as
the axis slowly shifts east. This is in response to a shortwave
trough which is currently approaching the Pacific Northwest
coast. This feature is forecast to crest the mean ridge position
as it translates inland later tonight through Friday, before
crossing northern Utah and southwest Wyoming Friday afternoon
through Friday night. This will bring another round of snow across
the higher terrain with a chance of rain or a rain/snow mix across
the northern valleys during this timeframe. As such have increased
the PoPs across the north considerably. Mid level ridging will
follow for Saturday, bringing and end to any lingering
precipitation.

.LONG TERM (After 12Z Sunday)...In large, ridging will dominate
the southeastern Pacific throughout the long term, shifting the
mean storm track north along the Pacific coast. This will be
further driven by a mean trough setting up over the gulf of AK,
with split flow existing further upstream. Several short waves, or
remnants of, remain forecast to traverse across the northern
Rockies within this regime, with southern fringes (or splits)
crossing the area throughout the long term period on the
downstream side of the ridge. None perceived to be very organized,
but each maintaining a semi- active pattern limiting persistent
inversion potential moving forward.

Model consensus continues to portray the first of these crossing
the local region Sunday Night through Monday, shearing inland and
with passage as the more dominant large scale feature driving
local weather will be the aforementioned ridge. A high likelihood
for modest at best precip exists exists for the mtn spines and
adjacent upstream valleys across the western portions of the area
during this time, but limited cold advection should retain mostly
valley rain as the primary p-type.

Ensemble means favor this pattern to hold pat thereafter, with
deterministic guidance suggesting maintenance of a dirty ridge
with several other weak disturbances crossing the area in rapid
fashion. Have limited confidence in the timing of these, thus have
leaned on blended guidance of slight chance/chance PoPs focused
over the north as the most likely outcome at this time.

&&

.AVIATION...Cigs are expected to remain below 6000ft AGL at the
KSLC terminal throughout the valid TAF period, with mountain
obscuration of local terrain remaining in place. Outside of this,
VFR conditions are expected to hold. Southeasterly winds currently
in place are expected to switch to a light northwest between
20-21z, but periods of light and variable conditions are expected.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...None.
WY...None.
&&

$$

Seaman/Merril

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For frequently asked questions about the Area Forecast Discussion
visit...
http://weather.gov/saltlakecity/general/afd_faqs.php


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