695
FXUS65 KSLC 220943
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
343 AM MDT Wed May 22 2024

.SYNOPSIS...Increasing southwesterly flow today will bring a
warming and drying trend, along with gusty afternoon winds. A cold
front will cross the area tonight through Thursday, bringing
cooler conditions region-wide, along with a chance of
precipitation across northern Utah. The weather pattern will
remain active into the weekend with a more potent system expected
Saturday.

&&

.SHORT TERM (Through 12Z/6AM Friday)...An upper low spreading into
the Pacific Northwest early this morning is beginning to induce
southwesterly flow aloft downstream across the northern Great
Basin. As this low continues to dig southeast today, this
downstream flow will continue to increase resulting in breezy to
windy conditions across the forecast area this afternoon. This
will also ensure deep mixing, allowing for a warming and drying
trend for all areas. Max temperatures will trend anywhere from 8
to 14 degrees warmer today, topping out in the low to mid 70s
along the Wasatch Front and points along the I-15 corridor, with
80s across the lower deserts of southern and eastern Utah.

The cold front associated with the approaching low will reach
northwest Utah by late afternoon, then slowly progress south
through northern and central Utah this evening through tonight,
and eventually cross southern Utah Thursday. Isolated to scattered
convection along this boundary late this afternoon and evening
will pose a threat for strong microburst winds given the deeply
mixed boundary layer and elevated flow aloft. Otherwise
precipitation will be largely confined to areas north of I-80
tonight into early Thursday, as the upper low pivots and swings
east through southern Idaho. Much cooler air will drop snow levels
to near 6000 feet after midnight with any lingering precipitation,
however any accumulation will remain minimal at best. This colder
airmass will knock 10-12 degrees off max temps for Thursday across
northern and central Utah, while southern Utah will remain windy
and mild until the front passes Thursday afternoon.

.LONG TERM (After 12Z/6AM Friday)...Starting out on Friday, a
somewhat diffuse remnant baroclinic zone will remain draped from
west to east, likely somewhere across central Utah. Anticipate a few
isolated showers to develop over the high terrain Friday afternoon,
especially near the remnant boundary. While still below
climatological normal for late May, temperatures north of the
remnant boundary should see afternoon highs rebound upward about 5-
10F or so in comparison to highs on Thursday.

Friday night into Saturday another shortwave trough and associated
fairly weak surface reflection will push into/through the region. As
a result, will see precipitation chances gradually increase through
the night, likely becoming maximized Saturday afternoon as the
trough axis and associated surface features look to move through. If
timing holds, will also see a bit of a boost given some daytime
heating. Overall the system still doesn`t appear too remarkable, but
will result in an uptick of more widespread scattered showers and a
few thunderstorms Saturday, with maybe a bit more noted along the
surface boundary. Given mean ensemble PWATs near to slightly above
normal, biggest concern would be any storms popping up and maturing
quickly enough over sensitive areas such as area slot canyons and
typically dry washes... Though even then it looks like mean storm
motion won`t be exceptionally slow or anything. All the same, those
recreating accordingly (or elsewhere around the forecast region)
should at least keep an eye on the weather conditions. Afternoon
highs across the northern 2/3 of the forecast area will remain
similar to that of Friday, while the southern 1/3 will see a
cooldown of a few degrees or so.

In general, anticipate activity to gradually wind down Saturday
night into Sunday, though some guidance (such as the deterministic
GFS) show a second more robust shortwave and cold front pushing
through. Looking at ensemble scenarios, about 60% or so show more of
a departing trough with maybe some weak ridging starting to nose in
from the west. This would be the drier/warmer of the scenarios.
Around 20% of ensemble members have a weaker grazing type of trough,
which would be more likely to yield a bit cooler and unsettled
weather, primarily for the northern portions of the forecast region.
The remaining 20% of ensembles paint a picture more similar to the
deterministic GFS with a stronger shortwave/cold frontal passage,
which would be the wettest/coolest of the outcomes, and likely allow
for some impacts to spread a bit further south.

Model guidance continues to yield good consensus in a ridge
gradually building over the region Memorial Day on into midweek.
While there are some differences noted in just how quickly the ridge
builds in, pattern is likely to feature a fairly quick warmup and
dry conditions. By Tuesday, afternoon highs look likely to be
running about 5-10F above climatological normal for late May, with
further warming likely Wednesday as the ridge axis is forecast to be
close to overhead. As of this morning`s run, the NBM now gives a 34%
chance for KSLC to see it`s first 90F or higher day of the year. For
some others who may be looking for chances at 90F+, NBM gives a 0%
chance at KEVW, 4% chance at KLGU, 10% chance at KOGD, and 13%
chance at KPVU. While 90F+ is almost assured for those down in Lower
Washington County, NBM also gives a 10% chance to hit triple digits
at KSGU for Wednesday`s high. Suffice to say, ready or not, a taste
of more Summer like conditions appears to be likely in some capacity.

&&

.AVIATION...KSLC...Gradual increase in VFR cloud cover ahead of
approaching system. Additionally, will see southerly winds increase
after sunrise, becoming gusty by mid morning on into the afternoon
hours. Some guidance sources suggest potential for periods of
westerly crosswinds mid afternoon Wednesday, which will be something
to keep an eye on. Otherwise, should see a somewhat dry cold frontal
passage (shower chances ~20-30%) ~03-05Z early Thursday, with a
period of gusty NW winds following frontal passage. Slightly lighter
NW winds then favored to persist on through Thursday morning.

.REST OF UTAH AND SOUTHWEST WYOMING...At southern terminals, TAF
period features clear to mostly clear skies, and largely diurnally
normal winds with some modestly gusty conditions expected through
the day Wednesday. At northern terminals, an approaching system will
result in a gradual increase in VFR cloud cover through the period.
Most terminals will see a favored south to west component to wind
directions through the day, with many locations seeing gusts during
the day in the 20kt to 35kt range or so (higher chances at more
exposed and typically gusty terminals). By late Wednesday evening, a
cold front will drop southward resulting in a flip to north-
northwesterly winds, including a period of gusty conditions
following the front. Widespread precipitation not expected, but
scattered showers likely to accompany the front, with highest
chances from N UT into SW WY.


&&

.FIRE WEATHER...A dry and mild southwesterly flow will spread
across the region today ahead of an approaching cold front. This
flow will allow for a warming trend drying trend across all areas,
as well as south to southwest winds gusting in excess of 30 mph
across all areas. The approaching cold front will reach far
northwest Utah this afternoon, then push through northern and
central Utah overnight. Dry, mild and breezy conditions will
persist into Thursday across southern Utah before the front passes
midday. Behind this front, a cooler and more stable airmass will
spread across the region, with any precipitation Wednesday night
through Thursday confined to northern Utah.

The pattern will remain active into the weekend, as a more potent
weather system moves into the region Saturday. Forecast models have
trended stronger and wetter with this system, and it`s looking more
likely that precipitation will be fairly widespread Saturday across
northern and central Utah, and perhaps more scattered across the
south. This precipitation may linger into the day Sunday, before
a warming and drying trend follows for the first half of next
week.

&&

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

$$

Seaman/Warthen

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