694
FXUS65 KSLC 281104
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
504 AM MDT Sun Apr 28 2024

.SYNOPSIS...Northwesterly flow will bring slightly below normal
temperatures across the region today. Southwesterly flow will
spread across the area Monday bringing a warming trend. A fast
moving cold front will cross the area late Monday through Monday
night, with a colder trough expected midweek.


&&

.SHORT TERM (Through 12Z/6AM Tuesday)...In the wake of an upper
low spinning over the central High Plains, a general northwesterly
flow aloft prevails across the forecast area early this morning. A
weak wave embedded within this flow has been driving a band of
shallow convection across northern Utah, which has been weakening
over the past hour or so as it crosses the Wasatch Crest. The
remnants of this band should clear the CWA by sunrise, with
lingering moisture coupled with daytime heating yielding isolated
to scattered showers across mainly northern and central Utah this
afternoon and early evening. With increased sunshine this
afternoon and gradually rising heights, max temperatures will
trend 5-8F warmer across the forecast area, reaching the low the
low 60s along the Wasatch Front southward to Cedar City, and 70s
across the lower elevations of southern Utah.

Southwesterly flow will increase Monday yielding breezy to locally
windy conditions across western Utah. Increased mixing coupled
with warming aloft will allow max temps to trend up another 5-8F,
with upper 60s along the Wasatch Front south to Cedar City, and
low 80s around St George and Bullfrog.

This increased flow is in advance of a shortwave trough which
will dig through the northern Rockies Monday, pushing a cold front
through northern Utah late Monday afternoon, then eventually into
central Utah Monday evening. Model guidance has trended a little
deeper with the parent shortwave with better jet support spreading
across the forecast area with the passing baroclinic zone. This
forcing will allow a broken band of precipitation to accompany
the frontal boundary as it pushes south through the area. Minimal
precip is expected in the northern valleys as this boundary pushes
through, with up to 0.25" QPF across the northern mountains
through late Monday evening.

.LONG TERM (After 12Z/6AM Tuesday)...Guidance remains in good
agreement that an active, progressive weather pattern will remain in
place with low probability of high impact weather over the forecast
area. Late Tuesday through Wednesday will feature a trough moving
across at least a portion of the forecast area, bringing wetter and
cooler weather. Thursday forward, there lies much more uncertainty
in the evolution of the pattern, with solutions ranging from a
cooler trough to a ridge that would bring warmer and drier weather.

Tuesday will start out dry with near seasonal temperatures across
the northern half of Utah and southwest Wyoming and above average
(by about 5-7 degrees) across the southern half of Utah. Afternoon
cloud development is expected across the northern half of the area
as moisture lingers, and a few of those clouds will develop into a
light shower (mostly over the northern mountains).

Tuesday evening through Wednesday, a shortwave trough is expected to
follow in the wake of the wave moving through on Monday. Ensemble
guidance still seems to be fairly split with how deep this trough
will become as it moves over the forecast area. While ~55% of
guidance supports a shallower trough that would keep a cold front
confined to the northern half of the area, the remaining 45% favor a
deeper trough that would introduce a colder airmass to much of the
region. From the deterministic guidance perspective, the guidance
remains fairly split with a slight favoring toward the deeper
trough. What this uncertainty means for the sensible weather will be
a lower confidence forecast in the temperatures for both Wednesday
and Thursday (i.e. the post frontal environment), particularly
across the southern half of the area. At this point in time, there
is still about a 6-10 degree spread in the most likely temperature
range for the Salt Lake City, Cedar City, and St. George areas.
Precipitation will accompany this system, but again, not expecting
any significant impacts as the high end of the most likely scenario
(e.g. 75th percentile) is generally less than 0.05" of rain. Will
likely see snow mix in at the higher elevation valleys, but not
expecting measurable amounts... moreso just snow in the air.

Moving past this trough there is a considerable amount of
uncertainty revolving around how quickly this trough moves out of
the area and how quickly a ridge builds in its wake (if at all).
Current model guidance is favoring a ridge developing over the West
late in the week/ early in the weekend. However, there are about 20%
of ensemble members that continue to favor a trough over the West.
Furthermore, there is even more uncertainty revolving around how
quickly the aforementioned ridge moves out of the region
thereafter... still a lot to work through, but thinking a warming
trend will be introduced through the second half of the week as the
aforementioned trough moves east of the area.

&&

.AVIATION...KSLC...VFR conditions are expected to prevail over the
KSLC terminal through the valid TAF period. Light southerly winds
will persist through the morning hours, reverting to a northerly
flow around 18Z. Afternoon cloud development is expected to generate
bases around 5kft AGL, which will likely lead to obscuration of
local topography.

.Rest of Utah and Southwest Wyoming...VFR conditions are expected
across a majority of the forecast area, with localized MVFR to IFR
conditions expected at higher elevation valleys across northern Utah
and southwest Wyoming. Isolated to scattered showers are expected
across the northern half of the area, however, no major impacts to
terminals are expected. Winds will favor diurnal trends through the
early morning, with northwesterly flow dominating most of the area
during the afternoon hours.
&&

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

$$

Seaman/Webber

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