Severe Thunderstorm Warning 5, NWS Salt Lake City, UT

Area Forecast Discussion
National Weather Service Salt Lake City UT
348 PM MDT Tue May 28 2024

.SYNOPSIS...A cold front will move through the region Wednesday.
Scattered showers and thunderstorms associated with the front
will bring a threat of lightning and gusty winds. Temperatures
behind the front drop to below normal, but by Friday onward
temperatures areawide return to near to above normal. Largely dry
conditions are also anticipated to settle in following Wednesday's
frontal passage.

&&

.SHORT TERM (Through 12Z/6AM Thursday)...Afternoon synoptic analysis
shows mid/upper level ridge axis beginning to shift east in
response to amplifying troughing into the PacNW. This has allowed
for some weak energy to advect through overhead, which in
combination with diurnal destabilization and mostly mid-level
moisture is resulting in isolated convection. Mostly have seen
convection tend to favor initiating off high terrain before
drifting northeastward, but have seen a bit of general initiation
over portions of western Toole and Box Elder County. With dry
subcloud layers, SPC mesoanalysis highlights the bulk of the
forecast region with DCAPE values at or above 1000 J/kg. As a
result, any convection that matures sufficiently will be capable
of gusty and erratic outflow winds as a primary threat in addition
to lightning. So far today have generally seen max gusts in the
35-50 mph range, but wouldn't entirely rule out a gust 50+ mph
from anything more robust. While a few showers may linger into
the evening, should see activity wane with loss of daytime
heating.

Wednesday continues to look like the more interesting day overall
in regards to convective potential. Model guidance continues to
show good consensus in a cold frontal boundary advancing into the
region as the aforementioned PacNW trough continues to deepen and
shift inland. Some minor differences are noted in exact timing,
but rough timeline has the front entering N UT and SW WY by late
morning to early afternoon, with the front continuing southward
through the afternoon hours, eventually making it into S UT by
late evening (though likely becoming more diffuse by then).
Sufficient moisture feed ahead of the front (ensemble mean PWATs
~100-150% of normal) in combination with extra synoptic support
and convergence along the front should result in scattered
convective development accordingly as the front moves into the
area. That said, CAM guidance ranges from very isolated (HRRR) to
more widespread scattered (high res NAM), with reality probably
somewhere more in the middle. CAMs do also suggest convective
potential becomes less likely as the front drops further into S
UT. While exact timing will influence the degree of
destabilization, HREF mean SBCAPE builds to ~300-1000 J/kg late
morning/early afternoon ahead of the front, and mean deep layer
shear remains in the 20-40 kt range or so. This combination will
be more favorable to allow stronger and more organized convection,
as well as potential for better shear/cold pool balance. As a
result, will have a threat of strong gusty winds with tomorrow's
convection, as well as potentially some small hail. Once again
anticipate convection to further wane in the evening as
instability decreases and the front continues to lose definition.
Aside from convection, cooling H7 temperatures behind the
baroclinic zone will result in much cooler overnight lows, with
more marked decreases the northern half of the forecast region
particularly.

.LONG TERM (After 12Z/6AM Thursday), Issued 404 AM MDT...Thursday
will begin a modest temperature drop in the wake of a cold front
Wednesday. But for the end of May, temperatures are forecast to be
very seasonal and very pleasant. The weather pattern headed into
and through the weekend look to bring rather mild conditions to
the region. Warming temperatures are forecast as southwest flow
arrives by Saturday with high temperatures near the triple digit
marker in St. George and in southeast Utah. High pressure is not
expected to leave the region anytime in this long term forecast.
In fact, there's little variance in ensemble models until next
week, where the question becomes, just how high will temperatures
climb with a building ridge?

&&

.AVIATION...KSLC...Isolated showers capable of gusty, erratic
outflow winds are likely through around 06Z. Light southeast winds
will prevail with mostly clear conditions once showers taper off
through around 16Z. A cold front will transition winds to northwest
around 16Z, with gusts around 20 knots through the afternoon. Clouds
will increase, with isolated to scattered showers and thunderstorms
from roughly 20-00Z. Gusty, erratic outflow winds are likely with
showers and thunderstorms.

.REST OF UTAH AND SOUTHWEST WYOMING...Isolated showers for southwest
Wyoming and northern Utah capable of gusty, erratic outflow winds
will last through around 06Z. Mostly clear conditions with light
winds are likely after. A cold front will track into northwest Utah
around 12Z, sweeping across southwest Wyoming and northern Utah
through the morning and southern Utah through the afternoon and
evening. Isolated to scattered showers and thunderstorms are likely
from roughly 20-03Z, with southwest Wyoming and northern Utah most
likely to get gusty, erratic outflow winds.

&&

.FIRE WEATHER...A cold frontal boundary will move southward through
Utah on Wednesday. The front will likely move through northern
Utah late morning on into the afternoon hours, and central Utah
thereafter from the afternoon into the early evening hours.
Moisture appears sufficient to produce some isolated to scattered
convection along the front, and with fairly high cloud bases,
anticipate convection to carry a threat of gusty and erratic
outflow winds in addition to sporadic lightning. The front will
begin to lose definition as it moves into southern Utah, and
convective threat looks lower accordingly. Colder temperatures set
in behind the front, with below normal temperatures on Thursday
(excluding southern Utah). Temperatures quickly rebound by Friday
on into the weekend, moving back above normal. Drier conditions also
appear likely as a ridge dominated pattern is generally favored to
develop at this time.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...None.
WY...None.
&&

SHORT TERM...Warthen
LONG TERM...NDeSmet
AVIATION...Wilson
FIRE WEATHER...Warthen

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

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