NWS Salt Lake City, UT wrote its last area forecast discussion before the first event at Feb 3, 4:10 AM MST, 7 hours 50 minutes earlier.
Area forecast discussion, Feb 3, 4:10 AM MST, 7 hours 50 minutes before
Area Forecast Discussion
National Weather Service Salt Lake City UT
410 AM MST Mon Feb 3 2025
.SYNOPSIS...A warm and windy southwest flow will reside across
the region through Tuesday. A series of storm systems will follow
beginning Wednesday, and continuing through the end of the week,
bringing cooler temperatures and the potential for precipitation.
&&
.SHORT TERM (Through 12Z/5AM Wednesday)...An unseasonably warm
southwesterly flow will reside across the forecast area through
the short term period. This will bring record challenging
temperatures, both daytime Maxes and high overnight Mins. As an
axis of 4-6C 700mb air spreads across the forecast area this
afternoon, temperatures will trend a little warmer than Sunday.
Mid and high level moisture will limit solar insolation somewhat,
however a tightening pressure gradient will support mixing of this
warm air aloft the surface. This is already evident early this
morning as south winds have kept overnight mins in the mid 40s to
mid 50s across most western valleys. With this mixing, afternoon
temperatures in the mid 60s to low 70s will be common across the
valleys south of I-80, which is 20-25F above climo.
This gradient will remain across the forecast area through the
short term, maintaining winds through the overnight hours and
keeping min temps elevated. Have trended overnight temps toward
the 95th percentile of the NBM, but in many cases may still be a
little on the low side based on what's currently occurring. The
airmass aloft cools slightly on Tuesday, however max temps will
continue to run 15-20F above climo, while overnight temps Tuesday
night remain near or above daily records as the southerly gradient
persists. Will need to monitor the Sevier Valley as well as
southern/eastern Tooele County, as the potential is there for
these areas to approach advisory level winds as well this
afternoon and again Tuesday.
Lower elevation winds today through Tuesday will be maximized
across favored areas of west central and southwest Utah, from
roughly Milford northward to Highway 6. Have gone ahead with a
Wind Advisory for these areas, and maintained it through Tuesday
night as winds will remain elevated through the overnight hours.
.LONG TERM...(After 12Z/5AM Wednesday)...Warm, deep-layer
southwesterly flow will remain in place at the start of the long
term period on Wednesday, resulting in another day of above normal
temperatures. Temperatures, however, will cool slightly across
northern Utah and SW Wyoming as a weak baroclinic zone is forecast
by the majority of the model suite to drop into this area. As a
result, record or near-record temperatures will be replaced by
those that are 5F-15F above normal across the north. Across
central and southern Utah, temperatures will remain 10F-15F above
normal. The above-mentioned baroclinic zone will be accompanied by
the passage of a progressive shortwave trough and 140kt jet
streak across the Northern Rockies, and this will provide enough
moisture and lift for a period of valley rain and mountain snow
showers from generally the Wednesday-Thursday morning timeframe.
Flow will remain roughly southwesterly, thus certain areas such as
Sundance and Ben Lomond are likely to be favored. Currently, the
most likely QPF amounts are around 0.50-1.00" in the most favored
areas, with generally 3-9 inches of snow for the Upper
Cottonwoods. QPF amounts have trended downwards somewhat from
earlier runs. There is a low chance that precipitation may end as
a period of light snow Wednesday morning across the northern
valleys, but this appears to have limited impact at this time.
Winds will remain breezy across many of the same areas once again
Wednesday, although speeds will come down a bit as the gradient
weakens. For most of the wind-prone locations of west- central and
southwest Utah as well as SW Wyoming, majority of the
southwesterly wind gusts are forecast to fall into the 35-45 mph
range, strongest during the afternoon.
A brief break in the action remains possible on Thursday, though
light mountain showers could continue if enough low-level moisture
remains in place. This activity will be light and
inconsequential, however.
Another system looms on the horizon for the Friday through early
Saturday timeframe. A trough moving into the western CONUS is
likely to pass across Utah between late Friday and early Sunday,
bringing a strong cold front and appreciable moisture Friday into
early Saturday. IVT and IWV plots do indicate the presence of a
weak Atmospheric River associated with this system. GEFS
trajectory is slightly less favorable for Utah and SW Wyoming,
with a moisture plume axis oriented more SW-NE. The Sierras would
tend to "eat" most of the moisture in this scenario. However, EC
members favor a trajectory that sneaks around the Sierras,
allowing for better moisture transport into Utah and SW Wyoming.
These differences partially explain some of the QPF spread.
Speaking of QPF, it had been trending upward with the past few
model cycles, but has appeared to level off now in the latest
runs, even decreasing slightly in the means. This system appears
to be comprised of 3 parts: 1) Pre-frontal warm advection
precipitation 2) Banded precipitation along the frontal passage
and 3) Post-frontal moist WNW flow with favorable orographics for
locations such as the Upper Cottonwoods. The first phase of the
system would tend to favor terrain that does well in SW flow. The
second phase of the system would be more productive for valleys
(with mainly rain ending as snow Saturday morning), and finally
the third phase of the system would be more productive for east
benches and terrain that does will in NW flow.
As noted previously, there is a decent subset of guidances that
indicates dry air mass moving in shortly after the passage of the
cold front, which would cut down on potential precip in the third
phase of the system. Temperatures are also likely to plummet down
to around -13C to -16C at 700-mb by Saturday morning. Thus,
valleys could see snow showers on Saturday...again, if that low-
level moisture lingers. Currently, most likely scenario for
northern valleys is a trace to 1", with generally 8-16" of snow
for northern mountains with locally higher amounts. We'll continue
to refine these ranges as the relevant timeframe approaches.
&&
.AVIATION...KSLC...Gusty south winds will continue through
tonight across the terminal, with gusts in the 25-30kt range
common. Best chance for stronger gusts than this will generally be
between 21Z-02Z, when high-end scenario gusts as high as 40-45kts
will be possible (10-20% chance). Otherwise, gusts will likely
settle back down into the 25-30kt range after 02Z. Southwesterly
wind shear at 2kft in place through 00Z, with speeds around 30kts.
After 00Z, wind shear strengthens, with SW winds of 50kts as low
as 2.5kft. VFR conditions, although some hazy conditions cannot be
ruled out due to blowing dust transported into the region from
the SW.
.REST OF UTAH AND SOUTHWEST WYOMING...VFR conditions largely
expected through this period outside of areas of blowing dust
across portions of southwest and west-central Utah. For southwest
Wyoming, gusts around 40 knots are likely, with occasional gusts
to 50-55kts possible during the afternoon. Low level wind shear is
likely for locations with south winds, as southwest winds around
30 knots are established near 2kft, strengthening to 40-50kts
after 00Z. Mostly cloudy or overcast conditions are likely for
southwest Wyoming and much of Utah, with fewer clouds throughout
southern Utah. This will be in the form of a mid-level cloud deck.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Wind Advisory from noon today to 4 AM MST Wednesday for UTZ115-
122.
WY...None.
&&
Seaman/ADeSmet
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