695
FXUS65 KSLC 151013
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
413 AM MDT Sat Jun 15 2024

.SYNOPSIS...A slowly approaching trough brings increased risk for
fire weather conditions today through the arrival of the
associated mostly dry cold front on Monday. Cooler temperatures
follow in the wake of the potent cold front on Tuesday, however,
warming temperatures are expected to follow through the second
half of the week.

&&

.SHORT TERM (Through 12Z/6AM Monday)...A broad trough begins
tracking inland into the western U.S. today, bringing an increase
in dry southwesterly flow across the forecast area. Cooler
overhead temperatures begin working into northern Utah and
southwest Wyoming, bringing continued slow cooling of surface
temperatures across this area. That said, will continue to see
high temperatures running around 5 degrees above normal. For the
southern half of Utah, we`ll actually see a bit of warming as
compared to yesterday which will push highs up to around 10
degrees above normal. Afternoon winds will be gusting anywhere
from 20 to 35 mph across Utah and southwest Wyoming, with the
strongest (30-35mph) winds expected in southwest Wyoming. For
southern Utah, elevated fire weather conditions begin ramping up
as relative humidity values drop into the single digits and
combine with breezy afternoon conditions (see Fire Weather
discussion for more). Red Flag Warnings remain in effect for fire
zones with critically dry fuels, though critical fire weather
conditions will not just be limited to these zones.

Late Saturday evening, a weak and shallow frontal boundary is
expected to drop into the western Utah which will help to keep
winds elevated during the overnight hours. While no precipitation
will be associated with this frontal boundary, it will help set
Sunday up to see further cooling across the northern portions of
the forecast area.

The aforementioned trough continues its progression into the area
through the day on Sunday, allowing winds to continue increasing
coincident with the increasing lower level flow. Peak wind gusts
will increase by around 5 to 10 mph across the southern and
eastern portions of Utah while a more stable airmass over the
northwestern portion of Utah will favor weaker winds. Again, fire
weather concerns will be elevated for the areas experiencing
stronger winds alongside low relative humidity (i.e. southern and
eastern Utah).

.LONG TERM (After 12Z/6AM Monday)...A dry but potent cold front
Monday will bring gusty winds, blowing dust, and a dramatic drop
in temperatures to 10-20 degrees below normal by Tuesday.

Early next week, a deepening West Coast trough will begin to track
inland and approach our area, with a 100kt 300MB jet rounding the
base of the trough axis over the Snake River Plain. Such a synoptic
setup is much more typical of spring than the summer doldrums
pattern we have been in lately. The depth of the trough axis is such
that precipitation is highly likely to remain well north of our area
into Idaho and Montana. Rather than precipitation, the arrival of a
mid-level cold front at the leading edge of the trough axis will be
marked by a potent drop in temperatures and a strong pressure
gradient. Despite ensemble mean temperatures trending a bit warmer
in recent runs, the magnitude of the temperature drop is still
impressive by June standards; for example, the current deterministic
GFS shows a range of 700MB temperatures of +14 over central Utah to -
6 over the far northwest corner of Utah. This will translate to
highs dropping into the 60 to 70s for central/northern Utah valleys
by Tuesday, a (likely) welcome relief from the recent heat, and lows
in the 20s in the mountains. In fact, parts of the Wasatch Back such
as the Park City area will be approaching the freezing mark early
Tuesday, which would merit a Freeze Warning according to local
seasonal criteria. Meanwhile, far southern Utah is likely to see a
much more muted drop in temperatures as the colder air will not
reach that far south. The only significant disagreement in global
ensembles is in the frontal timing, anywhere from Monday morning to
Monday evening for Northern Utah. This greatly impacts the highs
Monday afternoon (e.g. an 20 degree 10th-90th percentile spread in
the NBM for SLC).

The other potential hazard with this front is gusty winds and
blowing dust. Pre-frontal southwesterly winds over ridges of
central/southern Utah look to be in the 25-35+ mph range, while post-
frontal winds will feature a short period of strong winds (likely
underdone in global ensembles given the strength of the pressure
gradient). The typical favored windy areas post cold front, e.g.
Point of the Mountain to Eagle Mountain, could see very strong
winds, with a worst-case scenario of warning-level winds approaching
60 mph for a brief period. Such winds combined with largely dry
conditions are likely to kick up significant dust as well, and could
pose a hazard for any wildfire starts.

For the remainder of the workweek, heights will rebound quickly over
the Central Rockies as the mean trough axis retrogrades back to the
West Coast. By late in the workweek, increased mid-level moisture
will advect in just to our east, supporting some threat of
showers/thunderstorms over eastern Utah. That said, unless the
trough position sets up farther west than currently placed in
ensemble means, our area is likely to remain on the hot/dry/breezy
side of the trough, meaning that those conditions are expected to
return by the end of the week.

&&

.AVIATION...KSLC...VFR conditions will continue with only a few
high clouds. Overnight southeast winds are likely to switch to
northwesterly earlier than usual, around mid morning, with some
potential for notable wind shear with stronger northwest winds of 20-
30kt around 1kft AGL. There is a 30% chance that these winds will
mix down to the surface in the morning hours. Winds should decrease
by mid afternoon.

.REST OF UTAH AND SOUTHWEST WYOMING...Generally drier conditions
today with cumulus buildups limited to higher terrain east of US-89
and only a few isolated showers/thunderstorms east of KPUC.
Otherwise southwesterly winds for points south of around KDTA and
westerly to northwesterly winds elsewhere. Wildfire smoke over
central Utah could lead to a few areas of limited visibility around
terrain.

&&

.FIRE WEATHER...A period of critical fire weather conditions featuring
a hot, dry, and windy environment will begin to spread over Utah
today as an upstream trough slowly works into the western U.S.
From today through Monday, afternoon relative humidity values will
bottom out in the low-teens to upper single digits for a large
majority of the area alongside fair to poor overnight humidity
recoveries (ranging from around 30-35 percent in western Utah to
15-20 percent for southern and eastern Utah). Winds will gradually
ramp up through Monday, with peak gusts for Sunday and Monday
expected to reach around 35-40 mph for southern and eastern Utah.
Red Flag Warnings remain in effect for areas with critically dry
(or approaching critical) fuels.

A cold front associated with the trough will progress through
Utah through Monday through Tuesday morning, shifting winds to a
north to northwesterly direction across Utah. There is some
uncertainty on the timing of this frontal passage, so be sure to
monitor future forecasts. Winds in the post-frontal environment
may continue to gust upwards of 25-30 mph, and could remain
elevated through the overnight hours. Though a cooler airmass will
spread over the region by Tuesday, the dry nature of the airmass
will bring minimal relief to low relative humidity. The cooler
airmass departs the area by the middle of the week, bringing a
return to hot, dry, and breezy conditions.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Red Flag Warning from noon to 9 PM MDT Sunday for UTZ495-496.

     Fire Weather Watch from Monday afternoon through Monday evening
     for UTZ495-496.

     Red Flag Warning from noon today to 9 PM MDT Monday for UTZ498.

     Red Flag Warning from noon Sunday to 9 PM MDT Monday for UTZ497.

WY...None.
&&

$$

SHORT TERM...Webber
LONG TERM...Van Cleave
AVIATION...Van Cleave
FIRE WEATHER...Webber

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