418
FXUS65 KSLC 212201
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
401 PM MDT Tue May 21 2024

.SYNOPSIS...Warmer and drier conditions spread over the area on
Wednesday before the next cold front pushes into Utah. Thursday
will feature cooler temperatures as another cold airmass settles.
An active weather pattern remains forecast heading into the
weekend, with some uncertainty revolving around the forecast next
week.

&&

.SHORT TERM (Through 12Z/6AM Thursday)...A trough that brought a
cooler and more moist conditions to a large majority of the
forecast area will continue departing the region through the
evening hours. Afternoon instability driven showers have been
noted across the northeastern portion of the CWA as the mid-level
cold core moves across northern Utah and Wyoming. This cold core
continues its track eastward through the evening which, alongside
loss of heating, will contribute to decaying shower activity.

Thereafter, a brief period of zonal flow will take control of the
region in the mid-levels. Lower in the atmosphere, warm and dry
south to southwesterly return flow will bring a stout change in
conditions heading into Wednesday. As compared to Tuesday, high
temperatures on Wednesday will be on the order of 5 to 15 degrees
warmer. The higher end of this warming will be see across northern
Utah where highs will be pushing back into the mid-70s on the
Wasatch Front.

Increasing lower level flow ahead of the next cold frontal
boundary will bring breezy afternoon winds across much of Utah and
southwest Wyoming on Wednesday afternoon. With temperatures rising
and drier air being introduced to the area, these winds will
combine with the aforementioned and create areas of critical fire
weather conditions. See the "Fire Weather" section of the AFD for
more details.

The next cold frontal boundary begins pushing into northern Utah
late Wednesday/ early Thursday morning as another trough settles
over the West. The boundary looks to progress through the southern
Wasatch Front by 3-4AM Thursday, continuing its progression
through the day. As the boundary progresses across the northern
portions of the area overnight, precipitation looks to be limited
to the northeastern portions of the CWA as a deeper moisture
profile lacks for the remainder of the area. Even then, not
expecting much in the way of impacts. Could see some snow mix into
the higher elevation valleys of the Wasatch Back, Bear River
Valley, and Uinta Co., Wyoming, however, impacts/ accumulations
from snow are likely to be negligible given the warm antecedent
conditions and speed at which the boundary will progress.

.LONG TERM (After 12Z/6AM Thursday), Issued 409 AM MDT...
Long term forecast period begins with a shortwave trough moving
east into the Northern Rockies, with an associated cold frontal
boundary moving southward through Utah. This front continues to
appear fairly dry in nature, with most guidance (including what
limited high res CAM guidance is now available) suggesting just
some light showers along/near the front, and largely remaining
north of US-40 or so. Boundary still looks to stall somewhere near
to a bit south of the I-70 corridor as the parent shortwave
continues eastward, with much cooler postfrontal temperatures
settling. To that point, Thursday afternoon highs for locations
behind the front look to be around 5 to 15 degrees cooler than
that of Wednesday. Aside from temps/precip, still seeing potential
for some prefrontal wind gusts ~25-40 mph, generally across
southern and eastern Utah, as well as some gusty postfrontal winds
in portions of the southwest Wyoming. For Friday, remnant
boundary will likely remain draped somewhere across central Utah,
and help trigger some isolated to scattered diurnal showers as
weaker trailing energy advects through overhead. Airmass will
moderate during the day as well, so will see temperatures begin to
rebound back upwards.

Warming temperatures continue into Saturday as the old baroclinic
zone washes out and H7 temperatures increase. As a result, expect
daytime highs Saturday near to maybe a bit below climatological
normal for late May. Continued energy advecting through in advance
of another approaching shortwave will once again trigger some
isolated to scattered showers across the forecast region. General
consensus amongst guidance is that this shortwave and associated
cold front take a similar progression to the prior system Saturday
evening into Sunday, with the fairly dry front moving south and
stalling/washing out across central Utah Sunday. The exception to
this scenario appears to be something akin to the deterministic
Canadian model (and supported by ~30% of ensembles) where shortwave
is more disjointed/weaker, and thus any surface reflection is much
more muted. That would likely be a drier and more mild scenario, but
for now kept NBM guidance for Sunday which includes a cooldown of
several degrees from central Utah northward in addition to some
continued isolated to scattered showers.

A bit of uncertainty remains for Memorial Day, with around 55% of
ensemble membership supporting a quick building ridge, and the other
45% maintaining some sort of weak lingering trough influences. For
the ridge scenario, dry conditions and normal to slightly above
normal temperatures would be expected. For the weak/lingering
trough, a more muted warmup and maybe some isolated precipitation
chances (generally further north in the forecast region) would be a
bit more likely. In any case, little suggests anything of a washout
type of day or much in the way of anything substantial at this time,
but those with outdoor plans may want to keep an eye on the forecast
all the same. Almost all guidance then supports further building of
a ridge moving into midweek, with dry conditions and warm
temperatures favored. While out just beyond the general time period
of this forecast (and subject to change being over a week out),
current NBM guidance even carries a 25% chance for KSLC to see its
first 90 degree day on Wednesday 5/29. For context, the mean first
90+ degree day for KSLC specifically is 6/3, so not too far off all
things considered.

&&

.AVIATION...KSLC...VFR conditions will persist for the KSLC terminal
through the period. Conditions will remain dry with a few high
clouds. Northerly winds will transition to a southerly drainage flow
overnight.

.REST OF UTAH AND SOUTHWEST WYOMING...VFR conditions will persist
across the airspace. Dry conditions will continue with only a few
high clouds. A gusty northerly wind component across most sites will
weaken overnight as winds become light and variable.

&&

.FIRE WEATHER...A trough which brought a colder and more moist airmass
to Utah will depart the region today, allowing for a drier and warmer
southerly return flow to prevail across the region. Wednesday will
feature high temperatures that are 5 to 15 degrees warmer than what
has been observed across Utah on Tuesday, with the higher end of this
warming range expected across northern Utah. Drier air will cause
afternoon minimum relative humidity values to drop by 3-5% for most
areas. Additionally, an increase in wind speed is expected out of the
southwest and will create areas of critical fire weather conditions
across Utah, mostly confined to the western half of the state.

Another cold front begins pushing into Utah late Wednesday night
through Thursday morning, and will bring a low to medium (15-30%)
chance of showers and an isolated thunderstorm across the northern
Utah mountains. Passing showers will bring generally less than a
35% chance of a wetting rain. Temperatures and relative humidity
remain a bit more moderated through the late week and first half
of the weekend as an active weather pattern maintains a cooler and
wetter atmosphere. There is increasing confidence that a warmer
and drier pattern will spread over Utah next week, which may bring
some of the hottest temperatures so far this year.



&&

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

$$

SHORT TERM...Webber
LONG TERM...Warthen
AVIATION...Mahan
FIRE WEATHER...Webber

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