380
FXUS65 KSLC 152135
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
335 PM MDT Sun Sep 15 2024

.SYNOPSIS...Winds will become strong and gusty by Monday ahead of
an approaching fall-like storm system, with enough instability for
some strong to severe thunderstorms. The trough will cross the
area late Monday into Tuesday, bringing showers, primarily focused
over northern Utah, along with much cooler temperatures for the
entire area.

&&

.SHORT TERM (Through 12Z Tuesday)...Utah and southwest Wyoming are
under an increasing southwest flow aloft in between a ridge over
the central United States and a broad trough moving onshore along
the Pacific coast. In this flow, have seen increasing moisture
with instability being provided by shortwave energy ejecting out
ahead of the low. Convection this afternoon has been scattered,
high based, and primarily focused over the northern half of the
forecast area. Most of the convection will tend to diminish this
evening, with some storms continuing later over far northwest
Utah where better jet support exists. Temperatures today remain on
the mild side, near seasonal normals over southern Utah but in
excess of 5F above climo over northern Utah.

The Pacific low will slide into the Great Basin by tomorrow
afternoon, and southerly flow aloft will increase further. Flow
aloft is expected to be in excess of 50 kts over western Utah,
where ensembles indicate an 80 to 90 percent chance of wind gusts
exceeding 40 mph tomorrow afternoon. Going Wind Advisory covers
this threat well. Elsewhere, some isolated wind gusts to 40 mph
will be possible, but should not be long lived enough to warrant
any headlines. Position of the upper level jet on the front edge
of this trough will put much of Utah, particularly northern and
eastern portions, under an enhanced risk for more organized
storms, with some severe storms possible. Limiting factor for
storms tomorrow will be moisture, as a dry slot will limit
coverage over at least southwest Utah, but instability should be
sufficient. By late Monday, the trough will begin its slide across
northern Utah, bringing more widespread showers to that portion of
the area.

.LONG TERM (After 12Z Tuesday), Issued 417 AM MDT...A
continuation of a net northeasterly translation of the anomalously
deep upper low in place will occur Tuesday, with the core progged
to be over northwestern Wyoming by 00z Wednesday (filling as it
lifts). Through that period the cold core will be spreading across
the northern tier of the forecast area during the day Tuesday
aiding increased low level instability for a maintenance of
showers/storms across the northern third...most likely north of
the I-80 corridor. Much cooler temps associated with/post passage
into the midweek period, some 10-15 degrees below climo forecast
attm.

Providing the kicker for this first upper low will be a trailing
upper low that will take a further west/south trajectory as it
deepens along the Pac Coast and western Great Basin Wednesday, prior
to lifting ENE across the forecast area Thu-Fri (filling whilst once
again). On Wednesday the focused forcing will be tied to a
strengthening deformation axis centered to the west over Nevada, but
subtle differences in placement within ensembles of such a detail
remain. Consensus maintains chance showers focused generally over
northern/western portions (Wed) tied closest to this feature
however, and going forecast reflects this. Thereafter additional
shower/storm potential appears to be tied along and ahead of the mid
level axis passage and cold core as the trough progresses ENE across
the region through Friday. Primary takeaway with this trough is a
reinforcement of the unseasonably cool airmass, as only modest at
best precip is expected areawide, prior to a drying trend from W-E
to enter into early next weekend.

Globals continue to advertise a third upper low translating
southeast into the area later next weekend into early next week.
Lots of uncertainty in amplitude/track/evolution of this feature so
can`t resolve much more than yet another reinforcement of cooler
than normal conditions attm.

&&

.AVIATION...KSLC...Gusty southerly winds with 25-30kts will
continue, decreasing in speed after 02z. Isolated to scattered
showers and thunderstorms will continue to develop late this
afternoon and into the early evening, with the best chance for
thunder over the terminal between 23-02z. Gusty southerly winds are
expected once again tomorrow (Monday).

.REST OF UTAH AND SOUTHWEST WYOMING...Gusty southerly to
southwesterly winds will continue, decreasing in speed after roughly
02z. Scattered showers and thunderstorms (north of KCDC-KBCE) will
persist through roughly 03z, with a few heavier showers possible
through 07-08z across northern UT and southwestern WY. These storms
will be capable of producing gusty and erratic outflow winds.
Stronger southerly winds will return Monday afternoon with another
chance for showers and thunderstorms.

&&

.FIRE WEATHER...Seeing some high based showers and storms developing
this afternoon, primarily over northern and central Utah. Any
storms that develop will be capable of producing gusty and erratic
thunderstorm winds through the evening. As a Pacific trough
approaches tomorrow, winds will continue to increase over the
area, becoming strong and gusty, particularly over western Utah.
Dynamics will also become increasingly favorable for the develop
of showers and thunderstorms, particularly over northern and
eastern Utah, with some strong storms possible. RH values are
expected to stay at or above 20 percent Monday afternoon, which
will limit fire weather concerns somewhat. The storm system will
cross the area late Monday into Tuesday, bringing additional
showers to northern Utah and much cooler air across the area. The
cooler temperatures will persist for several days.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Wind Advisory from noon to 9 PM MDT Monday for UTZ115-122.

WY...None.
&&

$$

SHORT TERM/FIRE WEATHER...Traphagan
LONG TERM...Merrill
AVIATION...Cunningham

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