336
FXUS65 KSLC 200957
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
257 AM MST Thu Nov 20 2025

.SYNOPSIS...An active pattern continues with several upper level
lows crossing the region through Sunday. The northern stream
becomes active, bringing several disturbances through the West
Tuesday into Thursday.

&&

.DISCUSSION...An active pattern continues across the West, with
several upper level lows rotating through the mean flow. The first
upper level low is near Yuma, AZ this morning, followed by the
next one near the Washington Coast.

As far as this morning, dense fog has developed in several
locations. Across the Cache Valley and eastern Box Elder County
(particularly the I-15 corridor north of Brigham City to the Idaho
stateline), dense fog has developed. Visibilities at or below 0.25
mile to 0.10 mile have been reported in locations such as
Plymouth, Wellsville, Logan, and Richmond. Those with travel plans
across the Cache Valley and the I-15 corridor north of Brigham
City should be prepared for dense fog, with visibility quickly
dropping below 0.25 miles. Issued a dense fog advisory for these
locations through 8 AM.

Patchy dense fog has been reported in other areas such as Castle
Country, near Dugway, and in areas where stratus is intersecting
terrain. Will continue to monitor for expansion of the going dense
fog advisory.

As the upper level low near Yuma continues to shift east and then
northeast through early Friday and an upper level circulation
shifts across eastern Utah, valley rain and mountain snow will
continue across much of the region. Amounts will be light however,
with valleys largely ranging from around 0.05-0.15", mountains
seeing 0.10-0.25".

The next upper level low will be off the southern California Coast
Friday. This upper level low will shift east and the northeast
(just like the low previous) Saturday into Sunday. Around 25% of
the guidance brings the upper level low across the 4 Corners
area, with around 0.10-0.25" of valley rain/mountain snow across
southeastern and south central Utah Sunday. Around 25% shift this
upper level low further south, bringing around 0.05-0.10" of
precipitation to south central and southern Utah. The last 50% of
ensemble members are even further south and east and this path
would bring less than 0.05" to all but far southeastern Utah.
Regardless, all scenarios would remain below any advisory
criteria.

As the second upper level low ejects into the central Plains, the
northern stream begins to get more active across the region. A
digging upper level trough will impact at least portions of the
Intermountain Region Monday into Tuesday. There are wide
variations in depth and timing, with the majority of the ensemble
members keeping the best forcing for precipitation across
Montana, but bringing at least a weak, dry cold front into
northern Utah Monday into early Tuesday. Somewhere around 25% of
the ensemble members bring the shortwave trough through the
central Rockies, with a period of light precipitation associated
with the cold front across northern Utah. Either solution shows
little threat of impactful precipitation at this time, however,
with guidance suggesting around 0.05-0.10" of SWE for the northern
mountains.

Looking ahead to Thanksgiving...a jet max coincident with
northwest flow across northern Utah is increasing the threat of
precipitation...especially across northern Utah. Around 40% of
ensemble members bring 0.15-0.50" of precipitation to northern
Utah, highest in mountain areas. Right now there is about a 50%
chance of snow levels around northern valley bench locations
Thursday, around 25% for valley floors, lowest near the Utah/Idaho
border. Something to keep an eye on, but it`s still quite far
into the extended forecast period.

&&

.AVIATION...KSLC...VFR conditions will persist through the period
for the KSLC terminal. Isolated light showers are possible (30%
chance) throughout the day with CIGs lowering enough for
intermittent mountain obscuration. Winds will be light and
diurnally driven with some light variable winds associated with
showers.

.REST OF UTAH AND SOUTHWEST WYOMING...Mostly VFR conditions will
persist for the airspace with morning LIFR across valleys near the
Idaho border as dense fog continues through the mid morning.
Elsewhere, lowered CIGs causing intermittent mountain obscuration
and brief showers will be possible (30% chance) throughout the
period. Winds will be light and diurnally driven with light
variable winds near showers.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Dense Fog Advisory until 8 AM MST this morning for UTZ103-107.

WY...None.
&&

$$

Kruse/Mahan

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