FXUS65 KSLC 032237
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
337 PM MST Tue Dec 3 2024

.SYNOPSIS...Valley inversions will continue to strengthen through
the week and into the weekend. The next chance for precipitation,
and alleviating inversion haze, will be on Sunday.


&&

.DISCUSSION...Inversion conditions continue to strengthen and
deepen across valleys of central and northern Utah. Looking at the
12Z sounding from KSLC there is a deep inversion extending up
~5000 feet above the surface. This is about 1500 feet deeper than
the inversion from yesterday's 12Z sounding. The Utah Department
of Environmental Quality Air Quality Division is currently
forecasting Salt Lake and Davis to remain in orange/unhealthy for
sensitive groups conditions through at least Thursday. Other
monitored valleys across northern and central Utah are forecast to
hold onto at least moderate conditions through Thursday, with the
exception of Utah county that is currently forecast to reach
orange conditions by Thursday. 

In addition to haze, fog potential will increase with each passing
day, particularly in locations near bodies of water in valleys
such as near the Great Salt Lake and smaller lakes and
tributaries. These will be most prominent overnight and through
the morning hours. Valley cold pools will also continue to 
strengthen throughout the week as temperatures in the bottom of 
valleys will run much colder than those at higher elevations and 
mountain locations.

A weak shortwave on Friday continues to weaken with a trajectory
further away from the forecast area. This will do little to
improve inversion conditions. The next potential storm to help
vent out valleys is advertised to arrive on Sunday in most of the
ensemble members (~84%). Slightly less of the ensemble members
(~61%) show a wetter scenario with the remaining members bringing 
little to no precipitation. The long residence time over interior
Canada and the PNW could deplete a lot of the moisture the airmass 
has to work with by the time it arrives. The one thing that is
more certain to arrive with the airmass is much colder
temperatures as H7 mean temperatures are forecast down to -13C.
If moisture does accompany the front there should be cold enough 
air for snow down to valley floors.


&&

.AVIATION...KSLC...Persistent valley haze will bring high end MVFR 
conditions through the overnight hours, and borderline MVFR 
conditions during the afternoon. Slantwise visibility will be 
heavily restricted around sunset and sunrise. Otherwise, winds are 
expected to be generally light and follow diurnally driven upvalley/ 
downvalley trends.

.REST OF UTAH AND SOUTHWEST WYOMING...Urban haze along the Wasatch 
Front will bring high end MVFR conditions due to visibility 
restrictions through the overnight hours, with only minor 
improvements during the afternoon hours. Winds will be generally 
light and terrain driven across all terminals, with speeds less than 
7kts for most areas. There is about a 30-40% chance of fog 
development during the overnight hours for terminals on the Wasatch 
Back and in the Cache Valley.

&&

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

$$

Mahan/Webber

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