NWS Salt Lake City, UT wrote its last area forecast discussion before the first event at Feb 26, 4:00 AM MST, 5 hours earlier.
Area forecast discussion, Feb 26, 4:00 AM MST, 5 hours before
Area Forecast Discussion
National Weather Service Salt Lake City UT
400 AM MST Mon Feb 26 2024
.SYNOPSIS...A strong cold front will cross the region tonight into
Tuesday morning bringing a markedly colder airmass to the region
and snow to valley floors above 4000 feet. High pressure will
build into the area for midweek before another strong, cold
Pacific system will bring the potential for valley snow and much
colder temperatures to the region Friday into the weekend.
&&
.SHORT TERM (Through 12Z Wednesday)...A return to winter is in the
cards for the Beehive State with an arctic influenced trough
crossing the region through Tuesday (hope everyone enjoyed false
spring 1). Early morning upper air and satellite analysis
indicates a strong polar jet oriented from north to south across
the Gulf of Alaska into the Pacific Northwest. A shortwave trough
is located on the east side of the jet and will elongate into a
broader trough through the day today, digging south and east into
the Pacific Northwest. Meanwhile, an upper level low remains off
the southern California Coast with a pronounced subtropical jet
across the southern tier of the US.
The previously mentioned cold upper level trough will continue to
shift south and east through the afternoon and evening. The
associated strong cold front will reach northern Utah around 7-8
PM this evening. HREF frontogenesis fields correlate a strong
signal of a strengthening cold front shifting south and east
through northern and central Utah through Tuesday morning. This is
also well correlated with tight thermal packing at 700mb. At SLC
for example, 700mb temperatures will begin the evening around
~-4C, falling to near -15C by 12Z Tuesday. This front will cross
through southern Utah by Tuesday morning, bringing a much colder
airmass to the region.
With a strong, robust cold front, expect a quick transition to
snow for all valley locations above 4000 feet. A band of moderate
to heavy snow is expected to cross the northern Wasatch Front,
Cache Valley, Bear Lake and Bear River Valley and eastern Box
Elder county between 8 PM tonight and 2 AM Tuesday, the Salt
Lake, Tooele and Utah Valleys between midnight tonight and 6 AM
Tuesday. Expect strong, gusty winds up to 40 mph or so coinciding
with the moderate to heavy snow and rapidly falling temperatures.
Those with plans to be on the roads during this time should be
prepared for hazardous driving conditions. This front will
continue through central and southern Utah through Tuesday
morning.
With such a strongly forced band, expect a period of subsidence
for a few hours behind the band. This should eventually end across
northern Utah, with 500mb temperatures near -37C or so. With very
steep lapse rates and sufficient remaining moisture, expect snow
showers to redevelop Tuesday morning and continue into Tuesday
evening, when the loss of insolation will combine with the
back edge of the trough shifting out of the state.
While there may be lake enhancement to this precipitation on top
of the already steep lapse rates, do not expect a band of lake
effect snow at this time. With swift dry air advection, expect the
threat of any lake effect snow is minimal Wednesday morning.
Kept going winter weather advisories and warnings, adding Tooele
Valley to the winter weather advisory as conditions will be
consistent with other Wasatch Front areas. While this storm looks
to put down a quick 1 to 3 inches with the cold front, the
combination of very intense precipitation, strong winds, and
quickly falling temperatures will cause hazardous driving
conditions (as mentioned previously).
As far as the wind threat, continued the wind advisory for
northwestern Utah. Expect strong wind gusts pre-frontal from the
west to southwest, with a marked shift to the northwest between 6
PM and 8 PM, bringing a strong crosswind to I-80 through the Great
Salt Lake Desert. Current guidance suggests the wind threat will
largely end between midnight and 2 AM. If this continues, the wind
advisory may be canceled early.
Another wind advisory continues for Castle Country for early
Tuesday morning into Tuesday afternoon. The 00Z HREF suggests
these winds may actually peak earlier, around 9 PM Monday (70%
chance of gusts to 50 mph near Ferron) to about 1 AM Tuesday (30%
chance of winds gusts to 50 mph near Ferron). This HREF run has a
<30% of winds reaching wind advisory criteria after 1 AM Tuesday.
This may necessitate the adjustment of the going wind advisory.
Finally, issued a wind advisory for southeastern Utah. Guidance
indicates a 60%+ probability of wind gusts over 45 mph in this
area. Given 700mb flow between 40-50kts across the Grand
Staircase, greater Lake Powell area and the western Canyonlands
area, expect at least occasional gusts in the 45-50 mph through
this evening and into early Tuesday morning. This may bring strong
crosswinds to US-89 between Kanab and the Utah/Arizona border.
.LONG TERM (After 12Z Wednesday)...Through the day Wednesday,
will see cool and dry northwesterly flow behind the departing
trough shift more zonal to potentially subtle ridging. In any
case, the drier and more stable conditions will keep the area
devoid of precipitation. Additionally, will see temperatures
rebound a good bit from the prior day, though afternoon highs will
still fall near to around 5F below climatological normal for late
February. On Thursday, deep layer flow will begin to shift more
southwesterly as a large scale trough begins to sink through the
PacNW. While this will start to increase moisture advection into
the region, lack of more widespread synoptic lift will largely
keep the region dry, with perhaps some low end orographic
precipitation starting to work into the far northern Utah
mountains by later in the evening. Otherwise, will see a continued
warming trend to around 5F-10F above normal, and some marginal
wind gusts (~20-35 mph) in the afternoon particularly for portions
of western Utah.
Friday onward through the remainder of the forecast period, this
strong trough and an associated cold front will work their way
through the forecast region. While uncertainty remains on exact
timing as well as some of the more fine scale details/numbers,
signal in guidance remains favorable for a period of impactful
weather.
The potential for strong wind gusts continues to look fairly
impressive Friday and Saturday in the prefrontal environment as
700mb winds accelerate into the 40-70 kt range or so with the
advancing trough. Conditions appear favorable for some of this
high momentum air to mix down to the surface, either via thermal
mixing during the daytime hours (especially if skies can remain on
the clearer side), or potentially by precipitation helping mix
down strong winds. On Friday, NBM probabilities suggest around an
80% chance to see period of wind gusts in excess of 45 mph (Wind
Advisory criteria) for much of Utah's West Desert region,
including Milford. These chances decrease to around 50% near
Delta, and around 20% closer to the Salt Lake Valley. Even if sub-
advisory, elsewhere frequent gusts in the 20-35 mph range appear
likely. Similar probabilities are noted Saturday, with around
30-50% chance of wind gusts in excess of 45 mph also noted from
south central Utah up into The Swell and Castle Country. For both
days, the ECMWF Extreme Forecast Index highlights much of the
forecast region in shading depicting winds quite anomalous
relative to climatology, further enhancing confidence in the
likelihood of breezy conditions.
Strong southwesterly flow will help generate moist upslope
orographic precipitation for much of the mountainous terrain
Friday into Saturday, with precipitation then maximized as a
potent cold front looks set to move through. Exact timing of the
push of this sharp baroclinic zone remains a bit uncertain, but
combination of deterministic and ensemble guidance suggest
sometime from late Saturday afternoon to midday Sunday. Ensemble
75th/25th percentile 700mb temps start around -3C/-6C on the warm
side of the boundary, and fall to around -12C/-16C on the cold
side. In turn, would anticipate a quick drop in snow levels
(especially if the front is as sharp as some deterministic
guidance suggests), with p-type at lower elevations transitioning
to snow, and accumulating snow looking increasingly possible. If
nothing else, it appears like another good system for area
mountains in regards to water amounts with current suite of
guidance showing widespread amounts of 1 to 2 inches SWE, and
locally higher amounts possible in some typically favored spots.
Following the cold front, will see a very cold airmass settle
into the region as the base of the trough slides in. In addition
to temperatures falling to around 10F-20F below climatological
normal, will likely see some continued isolated to scattered
instability driven snow showers, though moisture will become
increasingly limited moving into early next week.
&&
.AVIATION...KSLC...Approaching system will result in increasing
southerly winds on Monday, likely gusting in the 20-30 kt range
through the afternoon (with ~20% chance of occasional gusts 30-40
kts). Isolated to scattered rain showers possible through the
afternoon, and will also carry wind gust threat. A well defined
cold frontal boundary expected to pass with most likely timing
~04-06z Tuesday. This will bring sharp NW wind shift and cooldown,
and likely a brief period of moderate to heavy snow along with
significantly lowered VIS/CIGS. Thereafter, winds relax somewhat
with lighter snow showers becoming more scattered through the
night.
.REST OF UTAH AND SOUTHWEST WYOMING...On Monday, anticipate
increasing VFR cloud cover in addition to gusty (largely southerly
favored) winds through the afternoon as a system approaches. Will
see increasing precipitation chances at northern terminals
through the afternoon as a cold front approaches. This cold front
quickly moves through from north to south Monday evening into the
overnight hours, bringing quick wind switch to NW, rapidly falling
temperatures, and likely brief period of moderate to heavy snow
with marked reduction to VIS/CIGS. Lighter and more scattered snow
showers remain possible thereafter through the night. Front will
bring increasing impacts to southern terminals by Tuesday morning.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Wind Advisory from 11 AM this morning to 5 AM MST Tuesday for
UTZ101-128-130-131.
Winter Weather Advisory from 11 PM this evening to 5 PM MST
Tuesday for UTZ102-105-106-118.
Winter Weather Advisory from 8 PM this evening to 5 PM MST
Tuesday for UTZ103-104-107-109.
Winter Weather Advisory from 5 PM this afternoon to 5 PM MST
Tuesday for UTZ108-125.
Winter Storm Warning from 11 AM this morning to 5 PM MST Tuesday
for UTZ110-112-113.
Winter Storm Warning from 11 AM this morning to 11 PM MST
Tuesday for UTZ111.
Winter Weather Advisory from 2 AM to 5 PM MST Tuesday for UTZ115-
116-122.
Winter Storm Warning from 5 PM this afternoon to 5 PM MST
Tuesday for UTZ117.
Wind Advisory from 5 AM to 5 PM MST Tuesday for UTZ120.
WY...Winter Storm Warning from 11 AM this morning to 5 PM MST Tuesday
for WYZ021.
&&
Kruse/Warthen
For more information from NOAA's National Weather Service visit...
http://weather.gov/saltlakecity