609
FXUS65 KBOU 040626
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1126 PM MST Wed Dec 3 2025

.KEY MESSAGES...

- Areas of dense fog north of Denver tonight to mid morning
  Thursday.

- Milder to end the week, but strengthening winds and increased
  potential for heavier and prolonged mountain snowfall into the
  weekend.

&&

.UPDATE...
Issued at 855 PM MST Wed Dec 3 2025

Stratus and very light snow/flurries continue to linger over the
western plains, the lower foothills and the plains south of I-70.
Areas of fog have developed across the northern half of the plains
as well. As some of the models indicate areas of fog and low
clouds for some of the plains, will update the grids in keep this
going longer. this evening.

&&

.SHORT TERM /Through Thursday/...
Issued at 314 PM MST Wed Dec 3 2025

Upper level trough over the region slowly continues to shift
east- southeast through tonight. Weak northeast upslope low level
flow ends and winds turn more westerly. Snow continues to end from
north to south, ending mid evening over the southern foothills
and Palmer Divide. Web cameras show roads are mostly wet across
the Denver metro area. As temperatures fall towards sunset, road
conditions may worsen. Best chance for slippery roads will be
south of Denver along I-25 and westward into the foothills. As far
as the Winter Weather Advisories go, already expired the north
ones where snow has ended. May be able to expire the Boulder and
Denver areas early, will see how the snow plays out. Plan on
keeping the Park County advisory going into the evening hours.

The easterly flow across the continental divide is producing
downslope conditions across Summit and Grand Counties, scattered
snow showers will remain possible through about sunset and
additional snowfall expected to be light and less than an inch.

Drier air spreads across the area tonight with mostly clear skies
expected for much of the area come Thursday morning. Some clouds
will persist in the mountains. Patchy fog will be possible with
the best chance for fog being north of Denver in Weld and Morgan
Counties.

Mostly sunny skies will lead to a warmer day Thursday. Fresh snow
on the ground likely keeps highs below normal with readings in
the 30s to lower 40s. Surface pressure lowers through the day over
northeast Colorado, increasing the pressure gradient across the
continental divide. Expect gusty west to northwest winds to
develop across the Front Range mountains and higher foothills
through the day Thursday with gusts to 40 mph possible.

&&

.LONG TERM /Thursday night through Wednesday/...
Issued at 314 PM MST Wed Dec 3 2025

The general pattern hasn`t changed much for the long term period,
with a gradual warming trend still expected into next week.
Multiple waves of mountain snow, becoming heavy at times, will
continue under increasing northwesterly flow aloft, while the
lower elevations will largely remain dry. Be prepared for winter
travel conditions if heading to the high country this weekend.

Orographic snowfall will return to the mountains beginning
Thursday night, as moisture and flow aloft start to increase with
a 150 kt upper-level jet approaching from the Pacific Northwest.
Cross- sections show a mountain wave signature in place, which
will bring gusty winds to the upper lee side of the Front Range
Mountains overnight (and potential for a pretty sunrise on Friday
morning!). Only light accumulations are anticipated overnight for
the northern mountains, though QPF was slightly increased for
this forecast package as ensembles show a slight uptick for the
Medicine Bow Range south to the Indian Peaks.

Mountain orographics will hold on to light snow across the higher
elevations through Friday (up to 5 inches for the Park Range, 1-3
inches for the Medicine Bow south to the Indian Peaks), before
synoptic forcings increase with the arrival of the aforementioned
jet, reinforcing mountain snowfall. The left exit region will
setup over the forecast area late Friday night, and the greatest
QG ascent is expected between 6Z-18Z (11PM-11AM) Saturday. With
steepening mid- level lapse rates and a hint of frontogenesis
expected, we could see some periods of heavy snowfall (1
inch/hour) with this system, especially for the Park Range and
Rabbit Ears Pass, where hazardous travel will be likely during the
aforementioned time frame, with snow covered roads and reduced
visibilities expected. Snowfall accumulations approaching two feet
will be possible between Saturday and Sunday in the Park Range,
with lesser totals expected for the Central Mountains, where the
I-70 corridor could see between 3-9 inches from Georgetown to Vail
Pass. The Medicine Bow south to the Indian Peaks will settle in
the middle, with 6 to 11 inches possible for elevations above
9,000 feet. Be prepared for winter driving conditions when
traveling into any of the high country this weekend.

While the plains are expected to largely remain dry, we did increase
PoPs for portions of the lower elevations on Saturday, where both
ensembles and deterministic guidance are now hinting at influence
from the left exit region of the jet aloft bringing some very
light QPF (~.01 to .05 inches) to areas along the Wyoming border,
but would like to see what the hi-res solutions grasp onto before
upping QPF any farther. The main story for the lower elevations
will be with temperatures gradually warming through the weekend,
reaching the 50s to kick off the week.

&&

.AVIATION /06Z TAFS through 06Z Friday/...
Issued at 1124 PM MST Wed Dec 3 2025

Satellite shows the MVFR stratus deck is in the process of eroding
off the foothills from the southwest as light downslope flow takes
shape. This will bring clearing skies overnight, but a small threat
of fog. Drainage winds are starting to kick in with a more
southerly flow close to 7-9 kts, which in theory should be enough
to keep fog out of the airports. It could be close, though, as
some short range models still show fog at KDEN now til ~15Z. For
now, we will continue with the VCFG in the forecast with only a
low probability (20-25%) of any meaningful fog.

Regarding winds, light southwest flow should persist til about
18Z. Then wind direction signals become mixed. Usually with snow
on the ground we end up with an afternoon wind out of the
southeast, but pressure gradients would suggest west/northwest.
For now, we`ll just go with VRB since wind speeds should remain
less than 8 kts and low confidence in any one direction
prevailing. Light drainage winds from the south/southwest will
resume rather quickly by 01Z Friday. VFR conditions will persist
once the stratus/fog threat end.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 10 AM MST Thursday for COZ038-043-044.

&&

$$

UPDATE.......66
SHORT TERM...12
LONG TERM.....9
AVIATION...20