947
FXUS65 KSLC 142303
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
403 PM MST Thu Nov 14 2024

.SYNOPSIS...Mainly dry, windy conditions will last through much of
Friday. As a cold front tracks in from the northwest, winds will
diminish as rain and snow push in. Rain and snow will last into
Saturday, with drier conditions for the end of the weekend.

&&

.SHORT TERM (Through 12Z/5AM Sunday)...A longwave trough off the
west coast of the U.S. is enhancing southwest flow throughout
southwest Wyoming and Utah. Upper diffluence upstream of the
trough has brought a shield of high clouds to southwest Wyoming
and northern Utah, limiting temperatures slightly. Elsewhere in
Utah, the enhanced southwest flow with mostly clear conditions
pushed temperatures to around 5-10F warmer than normal.

Winds will increase and build further northward for Friday as the
longwave trough tracks inland. As the storm system approaches,
isolated to scattered rain and mountain snow showers will push
into southwest Wyoming and Utah. Isolated to scattered showers
will last through much of the day. The trough will become
positively tilted around the same time a baroclinic zone pushes
into Utah. The boundary will track into northwest Utah Friday
afternoon and into the urban corridor of northern Utah Friday
evening. Valley rain and mountain snow is likely for southwest
Wyoming and much of Utah from when the front slides through into
Saturday morning. As the trough splits, a northern branch will
lift to the northeast and a southern branch will transition into a
closed low to the southwest. Snow will continue through much of
Saturday where there is moist upslope flow from the west to
northwest.

Snowfall accumulation of 6-12 inches is likely for portions of
the northern mountains, with the highest totals for the upper
Cottonwoods and for portions of the Northern Wasatch.

Forcing will be weaker further south as forcing diminishes, with
light snowfall accumulations for mountain locations.

.LONG TERM (After 12Z/5AM Sunday)...An exiting trough will leave
shortwave ridging in its wake for Sunday before a trough moves in
from the PNW Monday/Tuesday. Guidance is currently split 50/50 on
a drier trough vs a wetter trough, but temperatures will likely
be cold enough to favor snow down to valley floors (except for far
southern Utah). This trough clears the area by Wednesday with a
high amplitude ridge building into the region and persisting
through the remainder of the long term period. Despite the ridge
building back in, temperatures will remain 5-10 degrees below
normal for the long term.

It seems we are in a rinse-and-repeat pattern with modest PNW
troughs moving through the area delivering advisory level snow to
the mountains once or twice a week since late October. The trough
early next week is in line to continue that narrative. Currently,
50% of ensemble members favor a more direct hit from the approaching
trough (with the EC leading this charge) that would result in a
wetter scenario with colder air extending further into southern
Utah. The other 50% of membership (GEFS heavy) favor a more
northerly track that would keep the colder air further north with
less precipitation. H7 temperatures will be cold enough (ens. mean -
14C) to support snow to valley floors, aside from lower Washington
county.

The ceiling for this storm appears to be pretty low. When
looking at probabilities for snow totals >12" there is currently
only ~20% chance in the upper Cottonwoods and Tushars. This trough
quickly exits by late Tuesday with all of the guidance on board with
building a ridge into the west for the remainder of the period,
however we maintain a cold light northerly flow aloft that will help
keep temperatures below normal. Additionally, with subsidence
developing and a low sun angle we could start to develop more robust
valley inversions with haze and fog resulting that could keep
temperatures colder than forecast in these locations.

&&

.AVIATION...KSLC...Light winds expected to shift S between ~03-05Z
Fri, with high VFR cloud cover maintained overnight. Mid level cloud
cover begins to increase through Friday morning, with potential for
mountain obscuration by early afternoon. As a system approaches,
southerly winds will increase through Friday, with gusts likely in
the 25-30 kt range through the afternoon. Isolated showers (20-30%
chance) begin to develop late afternoon, with chances maximized
(70%+ chance) nearer to time of frontal passage after 00Z. Winds
will be favored to shift to a more W direction following frontal
passage. Snow levels initially around 5500 ft MSL Friday evening
fall to valley floor by Saturday morning.

.REST OF UTAH AND SOUTHWEST WYOMING...Quiet conditions with VFR
cloud cover and generally diurnally normal winds persist overnight
into Friday. Through Friday low/mid level moisture (~5-15 kft AGL)
and cloud cover increases as a system approaches. This will also
result in an enhanced southerly wind component at most terminals,
with likely gusts 20-30 kts at more exposed and typically windier
terminals (e.g. EVW/CDC/BCE). Precipitation chances gradually
increase from west to east through late afternoon Friday, becoming
maximized after 00Z on through the night as a frontal boundary
passes. This will favor most terminals to see a wind shift more W to
WNW or so. Snow levels initially around 4750-5250 ft MSL drop to
4500 ft MSL or less by Saturday morning.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Winter Weather Advisory from 3 PM Friday to 3 PM MST Saturday
     for UTZ110>112.

WY...None.

&&

$$

SHORT TERM...Wilson
LONG TERM...Mahan
AVIATION...Warthen

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