860
FXUS65 KSLC 012033
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
Issued by National Weather Service Grand Junction CO
233 PM MDT Wed May 1 2024

.SYNOPSIS...A cool but relatively stable airmass will reside
across much of Utah and southwest Wyoming today. The exception
will be southern Utah where scattered showers will persist
through this evening as a cold front moves out of the region. A
relatively cool and unsettled pattern will persist through the
remainder of the week, with the next weather system affecting
northern Utah and southwest Wyoming Thursday night into Friday.

&&

.SHORT TERM (Through 12Z/6AM Friday)...Showers have developed a
bit further west and south than most guidance indicated as the
tail end of the lingering frontal boundary continues to push
southward across southern Utah. Increased the PoPs in the near
term to expand coverage westward towards Bryce Canyon, with the
coverage remaining scattered south of a line from Bryce Canyon to
Capitol Reef through Canyonlands NP. These showers seem largely
driven by instability as lapse rates remain steep this afternoon
upwards of 8 to 9 C/km. This shower activity is fairly light with
mostly gusty winds upwards of 30 to 40 kts due to showers and
virga in some areas. These showers are expected to continue moving
southwest to northeast with the areal coverage slowly drifting
southward and out of the area by this evening. A shortwave trough
is pushing through across the north behind this boundary with some
CAA entering northwest Utah in the west-northwest flow as H7 temps
drop to between -7C and -9C. This should allow overnight lows to
drop below freezing across much of the area. However, a Freeze
Warning remains in effect for those areas that are most
susceptible, which includes East Box Elder County and the Utah
Valley (UTZ103 and 106). Even though other lower elevations fall
near to below freezing, they haven`t reached their average last
freeze dates, so no products remain in effect for those areas.
While there is some concern with cloud cover, it looks to remain
scattered overnight which shouldn`t impede those areas mentioned
in the Freeze Warning from reaching those conditions.

Temperatures on Thursday will rebound quite nicely as the cold air
retreats northward and WAA pushes in from the west and southwest.
Highs should warm up by about 5 degrees compared to today under a
westerly flow aloft with dry conditions expected. We are still
under the influence of the upper level trough that is still
sitting over the Intermountain West and Northern Rockies with yet
another shortwave moving across the north Thursday night into
Friday morning. This will generate some shower activity with some
high elevation snow but amounts at this time look minimal with a
few tenths to maybe an inch or two in the higher elevations of the
western Uintas and Bear River Range. Much of the central and
southern areas should remain dry throughout Thursday into Friday
morning.


.LONG TERM (After 12Z/6AM Friday)...The long-term period begins
with another shortwave trough grazing northern Utah, bringing
isolated showers to the northern third of Utah and southwest
Wyoming on Friday before drying out in the evening and overnight.
A shortwave ridge will then build across Utah on Saturday, but
this feature will be transient as another strong closed low
forming off the coast of the PacNW begins to move inland.
Increasing southwesterly flow is also expected on Saturday along
with strong warm-air advection with H7 temperatures reaching +7C
by Saturday evening. Ensemble guidance suggests H7 winds reaching
around 35-50kts across southwestern UT, with surface wind gusts
approaching High Wind Warning criteria (50kts)...something that
will need to be monitored in the coming days.

As the closed low continues inland, this will bring a potent cold
front through our forecast area later in the weekend. The main
impacts with this front will be a quick transition to
northwesterly winds, onset of widespread precipitation, potential
for thunderstorms along the frontal boundary, and snow levels
dropping to around 5500-6500ft. Winds could be quite gusty behind
the front; ensemble guidance suggests a mean of around 20-30kts at
700-mb, though the GFS is a bit more anomalous, reaching 45kts
over northern Utah. Precipitation chances will likely continue
through Monday as the parent trough continues to shift over the
western US, as well as the chances for afternoon thunderstorms
given steeper lapse rates under the cold core. H7 temperatures
will drop quite a bit with this trough, down to around -6C to -9C.

There is still a lot of uncertainty regarding the timing of the
cold front. This could move through as early as late Saturday
evening (21% of ensemble members) or as late as Sunday evening
(another 21%). The most likely solution is Sunday morning to
around mid day. The rest of the coming week looks to remain cooler
following Sunday`s strong cold front with a few shortwaves moving
through the northwest flow on the backside of the upper level
trough, keeping scattered showers early to mid next week in place
across the northern areas.

&&

.AVIATION....KSLC...Northwesterly flow will continue, with gusts
to 20kts possible mainly during the afternoon. Light, southeasterly
flow is expected around 09-10z. VFR conditions will prevail.

.REST OF UTAH AND SOUTHWEST WYOMING...Northerly to northwesterly
winds will prevail through the afternoon and evening across the
area, becoming gusty to around 20-25kts, especially across eastern
areas. These northerly winds will weaken, becoming light and
diurnally-driven overnight. VFR conditions will prevail.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Freeze Warning from midnight tonight to 9 AM MDT Thursday for
     UTZ103-106.

WY...None.
&&

$$

SHORT TERM...WFO Grand Junction
LONG TERM...WFO Salt Lake City
AVIATION...WFO Grand Junction

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