Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 171025
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
425 AM MDT Sun Mar 17 2024

.SYNOPSIS...Strongest easterly downslope winds are expected to
linger into Sunday morning, with the strongest winds gradually
becoming closer to the canyons of Weber and Davis counties for
this last phase of the event. Breezy canyon winds will continue
through Sunday night. Meanwhile, a closed low will continue to
bring rain and snow showers to southern Utah into Tuesday, with
the most widespread activity Sunday.

&&

.SHORT TERM (Through 12Z/6AM Wednesday)...Stubborn, closed upper
low remains parked near Phoenix, AZ early Sunday morning with a
strong ridge of high pressure in place across the PacNW. Model
consensus continues to suggest the low will move little through
Tuesday evening while undergoing slight, gradual weakening.
Meanwhile, the ridge is expected to inch southward towards the
Western Great Basin through this time. This configuration will
maintain an easterly flow across the area through Monday evening.
Downslope easterly wind event remains underway early this morning,
with the strongest winds near terrain and the canyons of Weber
and Davis counties, with the strongest gusts near Park Lane in
Farmington and the mouth of Weber Canyon. For a couple of hours
late Saturday night and early Sunday morning, winds topped 60 mph
from Centerville to the mouth of Weber Canyon. Winds have
decreased some from this peak, now centered in the 45-55 mph
range. This is a reasonable expected range for gusts through the
morning, with a slight increase in speeds expected shortly after
sunrise.

Models suggest a slight weakening of the pressure gradient and
700mb winds this afternoon, with another slight increase tonight.
Considered extending the Wind Advisory through tonight to account
for the forecast increase, but ensemble mean probability of 45
mph winds drops below 50% this afternoon and remains below 50%
tonight. In fact, probabilities for gusts to 45 mph drops down to
about 20% after 2PM this afternoon, but increases again to 50%
between 8PM and 11PM. Given the probabilities do not creep above
50% this evening, opted to not extend the Advisory at this time.
However, wouldn`t be surprised to see a few gusts to 45 mph this
evening in wind-prone locations, especially around Park Lane and
the mouth of Weber Canyon, as gusts to 45 mph is represented by
the ensemble max values. Breezy east winds will continue into
Monday evening, but will drop into the 15-25 mph range with a few
gusts to 35 mph through Monday morning. We finally begin to lose
the gusty east winds by Monday afternoon and evening, closing the
book on a prolonged easterly downslope wind event that began
Thursday morning.

Meanwhile, rain and snow showers will continue across southern
Utah through Tuesday afternoon, with the most widespread,
organized activity Sunday. Activity will become more spotty and
showery by Monday and Tuesday. Even so, today`s activity will be
lighter than the impressive amounts (there`s a 50% chance that
precipitation reached 1 in 100 year amounts for the time of year
in the Boulder Mountain and Henry Mountains area) of the past few
days. Biggest impacts today will be some winter driving conditions
(especially this morning along I-70 from Salina Summit through
higher elevations of the Swell) this morning. A few showers this
afternoon will be capable of easterly/northeasterly gusts in the
25-35 mph range. With so much rain and snow haven fallen over
southern Utah over the past few days, there is some concern about
possible snowmelt flooding as we get into the mid and especially
late week period. We will continue to assess this potential over
the next couple of days.

.LONG TERM (After 12Z Wednesday)...By Wednesday our cutoff low
responsible for the windy conditions across northern Utah and
bountiful precipitation across the south will finally be moving
east. High pressure will be left in its wake resulting in dry
conditions and temperatures 5-10 degrees above normal. The quiet
weather will be fleeting, however, as a trough will be moving in
from the PNW late in the week through the weekend. The timing of
this trough is still uncertain, but it will likely be ushering in an
active pattern that will potentially remain in place through the
following week.

By Thursday, southwesterly flow aloft will begin to advect moisture
back into the region. Thursday and Friday will likely stay mostly
dry across the region, but 44% of ensemble members do bring a
shortwave through late Thursday and Friday that could bring some
minor precipitation to the higher terrain. The remaining 56% of
members don`t have this feature and keep conditions dry and warm.
It`s not until the weekend that the aforementioned trough begins to
impact the region. This trough will be bringing decaying atmospheric
river moisture into the Great Basin. 44% of members have this trough
arriving on Saturday with widespread valley rain and mountain snow
initially. The remaining members delay this arrival until Sunday.
The focus for the heaviest precipitation will likely lie along a
baroclinic zone that sweeps through the area that could potentially
drop snow levels down to valley floors, but guidance has a wide
spread regarding how cold temperatures get. The H7 temperature
spread within the 25th-75th percentile ranges from ~-5C to -11C.
Regardless of precipitation type, most of the region looks to
receive another round of copious moisture with cooling temperatures
some time next weekend.

&&

.AVIATION...KSLC...VFR conditions will prevail across the KSLC
terminal through the period. Dry conditions and mostly clear skies
will persist with winds maintaining an easterly component. Brief
easterly gusts to 25kts will remain possible through the morning
hours before lighter winds settle into the area.

.REST OF UTAH AND SOUTHWEST WYOMING...VFR conditions will prevail
across the central and northern airspace with a few high clouds and
easterly winds continuing with brief gusts. Across southern Utah,
light precipitation and low CIGs will create intermittent MVFR/IFR
conditions before improving to mostly VFR in the afternoon. Winds
across the south will be light and variable.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Wind Advisory until noon MDT today for UTZ104.

WY...None.
&&

$$

ADeSmet/Mahan

For more information from NOAA`s National Weather Service visit...
http://weather.gov/saltlakecity


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