093
FXUS65 KBOU 061746
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1046 AM MST Sat Dec 6 2025

.KEY MESSAGES...

- Significant snow and wind event for the mountains through this
  evening. Heavy snow and gusty winds expected, with substantial
  travel impacts possible across most of the mountain corridors.

- Strong winds at times into early next week.

- Milder temperatures ahead, with above normal temperatures by
  early next week.

&&

.SHORT TERM /Through Saturday/...
Issued at 232 PM MST Fri Dec 5 2025

Mountain snowfall has overperformed today. Several ski resort snow
stakes have recorded over 6 inches of snow today, and CDOT webcams
have also seen periods of moderate snow and travel impacts across
portions of the I-70 corridor. At least a couple more hours of
snow showers is expected this afternoon before drier air (as seen
by water vapor satellite imagery) works back into the region by
the early evening hours. However, this will be short lived as a
more impactful wave of snowfall arrives a few hours later.

The first significant winter storm of the season is expected to
reach the forecast area by late this evening as a plume of deeper
moisture arrives. Model cross sections are quite favorable for
orographic snowfall, with moisture depths reach 400mb in a well-
aligned west-northwesterly flow. We`ll also have some upper level
support as a 140kt upper jet streak slowly sinks south tonight
into Saturday. While the mountains will see the more significant
snowfall totals, it looks likely that light to moderate snowfall
will also spread into the high mountain valleys by Saturday
morning. Moisture gradually diminishes during the daytime, but
there should be enough lift from the upper jet to at least keep a
few bands of snow around through most of the day. HREF mean/PMM
QPF totals through 00z Sunday are generally around 1-2" for the
Park Range and 0.75-1.5" for the Front Range and Summit County
mountains. Snowfall ratios will likely be a little lower than
climatology would suggest with this storm due to initially warm
temperatures and impacts from the wind (more on that below), but
snowfall totals should range from 4-10" across the mountain
valleys, 7-15" across the I-70 mountains, and 1-2 feet over the
Park Range. One thing worth watching is if guidance is a little
too dry with QPF for the latter half of the day... which could
lead to some localized totals up to 30" in favored terrain.

Perhaps more impactful than the snow will be the wind with this
event. A 75kt 500mb speed max tracks almost directly over the
mountains Saturday... with even stronger flow closer to 350-450mb.
With subsidence increasing behind the passage of a weak shortwave,
we should see widespread strong wind gusts develop during the late
morning to early afternoon hours. Guidance is in reasonably good
agreement advertising gusts of 35-50 mph across the mountain
valleys and 50-75 mph gusts across the mountain passes. Depending
on how much overlap there is between the moderate/heavy snow and
the increasing winds, there could be a period of near blizzard
conditions across portions of the high country. We`ve expanded the
Winter Storm Warning into Middle Park and issued a Winter Weather
Advisory across North Park due to the potential for snow and
blowing snow there.

Across the plains, dry but breezy conditions should develop during
the afternoon as mid-level flow and subsidence increase. Guidance
favors wind gusts of 30-50 mph across the metro and plains. A few
rain or snow showers may attempt to make it across the mountains
during the day but chances for measurable precipitation remain
quite low (<20%). Temperatures should also be a little warmer with
highs in the mid to upper 40s.

&&

.LONG TERM /Saturday night through Friday/...
Issued at 232 PM MST Fri Dec 5 2025

Will see mountain winds decrease Saturday evening as the strong
mid level flow shifts south. However, breezy to windy conditions
will prevail much of the night. Gusts of 20 to 30 mph are expected
with higher exposed areas seeing gusts up to 50 mph. The decrease
in winds leads to less orographic lift and a decrease in
snowfall. Travel Saturday night will remain difficult throughout
the mountains due to the continued light snow, recent snowfall,
and gusty winds. Up an additional 3 inches of snowfall will be
possible, most of this coming during the evening. Snowfall
continues to decrease and ends most areas Sunday as drier air
moves across the mountains. East of mountains, winds are expected
decrease Saturday evening, but are expected to increase again
Sunday, especially along the east slopes of the Front Range
Mountains and foothills where a mountain wave may develop where
gusts to 60 mph will be possible. Over the plains, winds increase
by afternoon with 40 mph gusts possible.

Northwest flow aloft will continue into next week around a large
upper level high off the California and Mexico coast. The main
storm track is expected to be north of Colorado with systems
grazing the northern mountains. The timing of these systems that
move across the mountains is somewhat uncertain, but there looks
to be one around Monday and a second one late Tuesday and into
Wednesday. Downslope flow east of the mountains will keep the
lower elevations dry and mild. Windy conditions will be possible
at times, mostly likely timing looks to be Monday night and into
Tuesday.

For Thursday and Friday, the position of the upper level high
will determine the weather across Colorado. At this time, models
show the upper level high drifting eastward with Colorado still
seeing a weaker northwest flow aloft. This is expected to bring
dry conditions throughout the area and continue the mild
temperatures. With this almost a week away, there is a chance the
high does not advance as far east as advertised. If this ends up
being the case, cooler temperatures and snow for the northern
mountains will be possible.

&&

.AVIATION /18Z TAFS through 18Z Sunday/...
Issued at 1046 AM MST Sat Dec 6 2025

Challenging forecast for the next six hours or so, until 00Z
Sunday. Northwest low level flow has produced an anti-cyclone with
north to northeast winds moving into DEN. This should decrease
the downslope component some and scattered showers will be
possible this afternoon. Expect winds to stay a northerly
direction (NW, N, or NE) through 00Z Sunday. Outflow from the
showers could produce gusts to around 30 knots. Expect the showers
to be mostly rain. A stronger shower could briefly produce snow
or graupel. Ceilings could fall to 5000-6000 feet under the
stronger showers. Winds are expected to become weaker after 00Z
Sunday and settle a southerly direction by 06Z.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 11 PM MST this evening for COZ030.

Winter Storm Warning until 11 PM MST this evening for COZ031>034.

&&

$$

SHORT TERM...Hiris
LONG TERM....12
AVIATION...12