Area Forecast Discussion
Issued by NWS Salt Lake City, UT
FXUS65 KSLC 272256
Area Forecast Discussion
National Weather Service Salt Lake City UT
356 PM MST Sun Nov 27 2016
.SYNOPSIS...A cold Pacific storm system will cross the region late
tonight through Monday. A cold northerly flow will follow through
midweek, with another storm system possible late in the week.
.SHORT TERM (Through 12z Wednesday)...Afternoon water vapor
imagery continues to depict a longwave trough encompassing the
western US, with several shortwave features rotating through the
mean flow. One such wave is currently digging through the Desert
Southwest, with the associated mid level trough axis crossing the
forecast area at this time. Weak ascent coupled with a moist
airmass is allowing for showers across much of the forecast area
this afternoon, however as this wave moves east of the area this
evening a brief break in precipitation is expected.
The next upstream wave, currently moving onshore along the Pacific
Northwest coastline, is forecast to quickly dig southeast through
the Great Basin late tonight through Monday. Warm advection ahead
of this wave will spread across northern Utah after midnight which
should allow snow to develop near the Idaho border, as well as
other areas of northern Utah typically favored in southwesterly
flow such as the Ogden Valley. Snow is expected to quickly fill
in during the morning hours Monday across northern Utah as the
parent wave approaches, becoming orographically enhanced in the
wake of the passing surface-700mb trough axis within a moist and
unstable northwest flow. Snowfall is expected to develop along the
I-15 corridor of central and southwest Utah during the afternoon
hours. As colder air filters into the region a favorable
environment for lake effect snowfall will set up over the Great
Salt Lake. At this time it appears this will initially impact the
Salt Lake Valley Monday evening, then shift west into the Tooele
Valley overnight into Tuesday morning.
Went ahead and upgraded the going Winter Storm Watch to a Warning
for the Wasatch Front, Cache Valley, and Wasatch Mountain Valleys,
where both the morning and evening commutes are expected to be
significantly impacted. Highest snow totals are expected along
the benches of the Wasatch Front owing to orographically
enhancement. Also issued Winter Weather Advisories for most of
western Utah, mainly focused on the Interstate 84 (Monday
morning) and Interstate 15 (Monday afternoon) corridors. Snowfall
in these areas will likely also impact travel, but due to a
shorter snowfall duration amounts are not expected to be as great
as the Wasatch Front.
Additionally, winds will be gusty and potentially strong in the
wake of the cold front during the day. Held off on headlines for
now, although may need wind advisories for both northwest Utah and
Castle Country Monday afternoon and evening.
.LONG TERM (After 12Z Wednesday)...The trough continues to exit to
the east on Wednesday, with shortwave ridging building over the
Great Basin. Any warming of temperatures is not expected to be
significant, especially since the next trough in the mean northwest
flow pushes into the region starting Wednesday night.
The bulk of the mid and upper level energy stays west and south of
the area Thursday and Friday, though Utah does get some weak and
moist cold advection. This could kick off some light shower activity
across the state, especially on Thursday and Thursday night. Have
continued to slowly increase POPs and sky cover through this period,
though precipitation totals do not look significant at this time.
Most of the trough is south of Utah by Friday night, with a more
stable anticyclonic flow setting up over the Great Basin. The
weekend still looks primarily dry across the area, though increased
cloud cover is possible across the north as the ridge flattens and
increased moisture moves over Idaho.
.AVIATION...West-northwesterly winds at the SLC terminal
should switch to the southeast around 07-09Z, though there is a
chance that this switch occurs as early as 04Z. Ceilings are
expected to hover in the 6-8kft range overnight until they lower
significantly again after 10Z Monday.
UT...Winter Storm Warning until 5 AM MST Tuesday for UTZ007>010-517-
Winter Storm Warning from 2 AM to 11 PM MST Monday for
Winter Weather Advisory from 2 AM to 11 AM MST Monday for UTZ005.
Winter Weather Advisory from 11 AM to 11 PM MST Monday for
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