166
FXUS65 KSLC 171026
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
426 AM MDT Mon Jun 17 2024

.SYNOPSIS...A strong cold front will cross the region Monday,
bringing a much colder airmass to the area for Tuesday.
Temperatures will quickly moderate midweek, with another period of
very hot temperatures by Sunday.

&&

.SHORT TERM (Through 12Z/6AM Wednesday)...Primary focus in the
short term period of the forecast revolves around an unseasonably
strong cold front that will blast across northern Utah and SW
Wyoming this afternoon, central Utah this evening and southern
Utah late this evening and overnight. Ahead of the front, breezy
S-SW winds will increase into the 30-40 mph range, with the
strongest winds along and east of Utah`s mountain spine. High-res
model mean suggests the cold front will enter northwest Utah
around the Noon hour today, surge south across Dugway by 3PM and
crossing the Wasatch Front between 2PM and 5PM. By 9PM, the front
will have reached the Uinta Basin, Castle Country, and will be
blasting through the Black Ridge Canyon between Cedar City and St.
George. Model consensus suggests widespread gusts in the 35-45
mph range will accompany the front, and persist behind the cold
frontal passage for 1-3 hours most areas, along with an abrupt
shift in wind direction to the N-NW. Wind-prone locations in such
a regime such as Park Valley, the I-80 corridor between Wendover
and Tooele and northern Utah Counties will have the potential to
experience locally stronger winds for a longer duration. Given
favorable stability profiles, we can`t rule out a brief (2-6 hour)
period of gusts in the 45-55 mph range here. Timeframe for this
period of locally terrain- enhanced stronger gusts is between
3PM-7PM along the I-80 corridor and Dugway, and between 4PM and
8PM across northern Utah County.

The thermal gradient across this front is truly quite impressive,
with forecast 700mb temperatures at 6PM this evening ranging from
minus 3C at SLC to plus 17C at Moab! Temperatures will fall
rapidly behind the front. With such an extreme temperature
gradient, some locations will be primed to exceed model mean
gusts. We think one of those areas will be across Castle Country,
where confidence is highest in Wind Advisory wind thresholds (45
mph gusts for 3 hours or more) being reached. Here, between 6PM
and 3AM Tuesday morning, gusts in the 45-55 mph range are likely.
It`s worth mentioning there is a low, or 10% chance for gusts as
high as 70 mph near canyons of Castle Country. As a result, have
issued a Wind Advisory for Castle Country to address this hazard.
Gusts will also likely top 45 mph through the Black Ridge Canyon
between 9PM and the early overnight hours, but confidence is not
high enough in widespread geographical extent of winds for 3 hours
or more. Nonetheless, folks should be prepared for strong
crosswinds on east-west routes behind the front, patchy blowing
dust and isolated instances of tree and powerline damage. Expect
rough chop on area waterways as well. It is recommended to secure
loose, lightweight objects.

Temperatures will be cold enough behind the front to support
freezing temperatures in outlying areas of the Wasatch Back
Tuesday morning, including such areas as Park City and the Ogden
Valley, including Eden and Liberty. For this reason, a Freeze
Watch remains in effect for these areas. Across the Wasatch Front,
temperatures will plunge into the 40s. Across outlying areas of
the Cache Valley, temperatures may approach 32F as well, with
just under a 10% chance of reaching 32F Tuesday morning in Logan.
Additionally, should enough moisture be in place, a few lake
induced showers may develop downstream of the Great Salt Lake,
with lake effect probabilities approaching 20% this evening.
Temperatures will be cold enough to support snow showers up the
Cottonwoods, but temperatures will remain warm enough to favor
rain in the Salt Lake Valley and adjacent benches.

.LONG TERM (After 12z/6AM Wednesday)...Following the much
anticipated early week trough, model guidance maintains good
agreement on meant troughing remaining in place to the west of the
forecast area through much of the upcoming week. An upstream trough
will promote increasingly warm southwesterly flow which will
strongly favor temperatures warming from right around climatological
normals on Wednesday to well above normal by Sunday. In fact, by
Sunday the Salt Lake City area could see another shot at 100 degrees
as model statistics support a 50 percent chance of exceeding 99
degrees and a nearly 40 percent chance of exceeding 100 degrees! For
the St. George area, temperatures could easily rise back into the
mid-100s. For both of these areas during the overnight period lows
may only drop into the mid-to-upper 70s, providing very little
recovery for those without proper cooling. There is generally medium
to high confidence in this warm up through the second half of the
week. As such, will need to evaluate heat risk for these areas over
the coming days as headlines may need to be considered.

Another aspect of the forecast that will be a welcomed change is the
increasing confidence in the introduction of moisture over the
eastern half of Utah late in the work week. Leading up to about
Friday, dry and breezy southwesterly flow will keep much of Utah
with elevated, to near-critical, fire weather conditions. However,
models showing increasing potential for moisture to ooze in from the
Gulf of Mexico and spread across the eastern half of Utah. Most of
the moisture increases are noted in the lower-to-mid levels which
will help to destabilize the atmosphere and bring potential for
stronger thunderstorms over the eastern half of Utah. GEFS and EPS
both show precipitable water levels upwards of 190 to 250 percent of
normal by Friday, respectively. This potential moisture flux could
very well give us one of our first hydrologically concerning events
for slot canyons, slickrock areas, and burn scars. After Friday,
moisture wanes and we return to mostly dry conditions across the
area... though isolated showers and thunderstorms are likely to
linger across the eastern half of Utah through at least Saturday.


&&

.AVIATION...KSLC...A cold front moves across the region today,
allowing for light southerly winds to switch to a northerly flow
around 15Z. Gusty afternoon winds are expected over the airfield,
where gusts will peak around 30-35kts. Lower level clouds will
increase during late afternoon/ early evening, obscuring local
topography but still remaining above VFR thresholds.

.REST OF UTAH AND SOUTHWEST WYOMING...A cold front will progress
across the region today, progressing from northern Utah early this
morning, through the Wasatch Front through the mid-morning, and into
southern Utah by the evening. Winds ahead of the front are expected
to remain elevated, with gusts around 30-35kts. Behind the front,
similar gust speeds are expected but out of a northerly direction.
Shower activity is expected across the northern third of Utah and
southwest Wyoming, with isolated snow showers being very possible in
southwest Wyoming after sundown and before midnight.

&&

.FIRE WEATHER...A strong, mainly dry cold front will cross the state
Monday into Monday night. Ahead of this front, expect gusty
southerly winds across southern Utah with very low humidities. The
front will bring an abrupt change in wind direction to the north
to northwest...remaining strong and gusty for several hours behind
the front. Wind gusts in the 35-45 mph range will be common along
and behind the front with locally stronger gusts. The front will
cross northern Utah in the afternoon, central Utah in the evening
and southern Utah from late evening trough the overnight hours
Monday night. While temperatures will be considerably cooler in
many locations Tuesday, humidities will not rebound much across
southern Utah. Another round of critical fire weather conditions
is possible Thursday into Friday across southern Utah as southwest
winds increase ahead of the next system. Mid-level moisture may
increase by Friday, spreading west from the Gulf of Mexico, which
may bring lightning to areas that have been very dry for a
considerable period of time across southern Utah. Something to
watch moving forward.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Freeze Watch from this evening through Tuesday morning for
     UTZ108.

     Wind Advisory from 6 PM this evening to 3 AM MDT Tuesday for
     UTZ120.

     Red Flag Warning until 9 PM MDT this evening for UTZ495-496.

     Red Flag Warning until 3 AM MDT Tuesday for UTZ498.

     Red Flag Warning until midnight MDT tonight for UTZ497.

WY...None.

&&

$$

ADeSmet/Webber

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