Avalanche in Utah, January 10, 2023

Area Forecast Discussion
National Weather Service Salt Lake City UT
423 AM MST Tue Jan 10 2023

.SYNOPSIS...A moisture rich Pacific storm system will bring
periods of lower elevation valley rain and significant mountain
snow through Wednesday. High pressure will temporarily move in
for the end of the work week before a series of storm systems
impact the area this weekend into early next week.

&&

.SHORT TERM (Through 12Z Thursday)...Utah and southwest Wyoming
remain under a rather moist southwest flow this morning as the
first of two troughs slides across the area. Associated
precipitation is heaviest over northern portions of the forecast
area, with snow levels in the 5500-6500 foot range, though some
pockets of lower snow levels are likely with heavier rates. Also
seeing a secondary maximum of precipitation over southwest Utah,
which could result in some enhanced totals for the Pine Valley
mountains as well as Brian Head. Seeing some strong, gusty winds
continue on the leading edge of the trough over the Tooele valley
as well as west central and southwest Utah, with some gusts in
excess of 40 mph. Going headlines cover these threats well.
Precipitation, heavy at times, will continue through the morning
before the first trough exits, allowing very brief shortwave
ridging to develop. As a result, anticipating a relative lull in
precipitation late morning/early afternoon with winds trending
downward as well.

The second larger trough will move into the Great Basin during the
day, with the cold front on the leading edge of the trough
approaching the Utah/Nevada border late afternoon. The arrival of
this trough will allow rain and snow to redevelop, initially
heaviest over southwest Utah in conjunction with the best short
wave energy and jet support. During the evening and early morning
the cold front will slide roughly west to east across the state,
and with good fgen forcing it is likely a good band of precip will
develop with some fairly intense rates. Snow levels will likely
drop quickly during this time, reaching most valley floors, and
higher snow ratios will result in less dense snow for the higher
terrain. Overall, have continued to nudge snowfall totals up just
a bit as models come into better agreement with regard to some
higher totals. Snow will continue through Wednesday morning,
becoming increasingly focused over the mountains of northern Utah,
before tapering off Wednesday afternoon.

.LONG TERM (After 12Z Thursday)...A short-lived ridge builds into
the Great Basin by Thursday before the return of more unsettled
weather on Sunday. This active pattern looks to persist through the
remainder of the long term period.

There is nearly perfect agreement amongst ensemble members about
this ridge of high pressure. It will bring a return to southerly
flow aloft which will help temperatures stay 5-10 degrees above
normal for most of the CWA, aside from lower Washington county where
temperatures will be near average. In addition to the relatively
warm temperatures, a rare (as of late) glimpse of sun will be most
likely on Thursday afternoon before clouds begin to increase again
ahead of our next storm.

A shortwave moves through early Saturday which will only result in
cooling aloft and small precip chances for the northern mountains.
This is ahead of a much more potent longwave trough arriving late
weekend. There is quite a bit of uncertainty in regards to the
trajectory, both spatially and temporally, of this trough. About 50%
of members have the trough digging further south bringing a bulk of
the precipitation further south across southern Utah and Arizona.
The other half keeps precipitation further north. Regardless,
temperatures aloft appear cold enough to support valley rain
transitioning to snow with any remaining precipitation on the back
end of the storm. Another trough quickly follows in the footsteps
Monday/Tuesday. This trough appears colder in nature.

&&

.AVIATION...KSLC...VFR conditions will prevail for the KSLC terminal
through tomorrow afternoon. Southerly winds >10kts will continue
through the period with gusts near 20kts. CIGs will hover near
mountain obscuration levels before rain pushes into the terminal
near 00Z.

.REST OF UTAH AND SOUTHWEST WYOMING...Rain and higher terrain snow
is pushing out of the area turning IFR/LIFR to MVFR/VFR as the day
progresses and CIGs/VIS improves. Mountain obscuration will still
remain for the northern half of the area. Another areawide storm
arrives this evening bringing a quick burst of rain and snow that
will drop conditions to IFR/LIFR.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Wind Advisory until 5 AM MST early this morning for UTZ102.

     Winter Weather Advisory until 5 PM MST Wednesday for UTZ107>110-
     113-114-117-120-125.

     Winter Storm Warning until 5 PM MST Wednesday for UTZ111-112.

     Wind Advisory until 8 PM MST this evening for UTZ115-122.

WY...Winter Weather Advisory until 5 PM MST Wednesday for WYZ021.

&&

SHORT TERM...Traphagan
LONG TERM/AVIATION...Mahan

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http://weather.gov/saltlakecity

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visit...
http://weather.gov/saltlakecity/general/afd_faqs.php