591
FXUS65 KBOU 091729
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1029 AM MST Tue Dec 9 2025

.KEY MESSAGES...

- Strong, damaging winds across much of our foothills and east-
  facing mountains through Tuesday evening, with gusts 75-90 mph
  expected.

- Locally strong winds may spread into wind-favored lower
  elevations at times today, with lower confidence. All areas
  will be breezy regardless.

- Northern mountains will see on/off light mountain snow into
  Wednesday.

- Another chance for a high wind event along the Front Range
  mountains Wednesday night into Thursday morning.

&&

.UPDATE...
Issued at 330 AM MST Tue Dec 9 2025

The decision was made to upgrade the High Wind Watch to a High
Wind Warning for Fort Collins, Boulder and the western suburbs of
Denver, as well as northern Weld County. There were two main
considerations for issuing the warning. First, the High Wind
Warning for the mountains and foothills is already verifying with
gusts in the 80s including an 81 mph gust at Dakota Hill. The
other consideration was that model guidance had a slight eastward
shift in the strongest winds likely due to better stability in the
forecast. The risk was too high that the western part of the city
of Boulder and the usual windy spots along Highway 93 get 75 mph
wind gusts to not have any highlights out. The eastern part of the
High Wind Warning, that includes the towns of Longmont, Arvada,
and Lakewood, may not hit High Wind Warning criteria but it is
expected the western part of the warning will hit criteria.

&&

.SHORT TERM /Through Tuesday night/...
Issued at 257 PM MST Mon Dec 8 2025

Current conditions out there are reminiscent of a typical late
fall day, with temperatures hovering in the mid/upper 50`s in the
plains, and around the freezing mark in our high valleys.
Nocturnal temperatures will be on the milder side with downslope
flow in place east of the Continental Divide, and ample cloud
cover over the high country. Meanwhile, areas of breezy west
winds are punctuating the landscape, of course being strongest and
most consistent above 9,000 ft where a few locations continue to
gust above 60 mph.

As we enter the overnight period, ingredients will begin to come
into better alignment to produce a steady increase in wind speeds
over our leeward mountains. By sunrise, cross-barrier flow looks
to be near 55-65 kts, with rapidly increasing east-west pressure
gradients. Everything points to a high confidence damaging wind
event for our central/northern foothills and leeward Front Range
mountains persisting well through the day Tuesday. Hi-res guidance
is all in on impressive 75-90 mph wind gusts becoming rather
widespread by early morning for these locations, and the list of
ingredients which support this is long:

 - Strong cross-barrier flow: Check
 - Stable layer near 600mb: Check
 - Robust pressure gradients: Check, check and check! (GJT-DEN
   gradients progged to peak between 16-19mb...)
 - Little to no speed shear above ridgetops: Check
 - Shallow moisture upstream: Check
 - Consistent QG subsidence: Check

The larger question revolves around the propensity of said winds
to spread east out of the foothills and impact some of our lower
elevations. Guidance is far from convinced about this, which
certainly reduces confidence in such a scenario. Suspect that this
could be due to a lack of any pronounced critical layer aloft - a
limiting factor, no doubt. Nonetheless, it seems far-fetched for
our more wind-prone lower elevations (e.g. Highway 93 corridor) to
not see incursions of 75+ mph gusts throughout the day Tuesday,
particularly past mid-morning, just given brute force alone and
the above recipe. With that in mind, seemed prudent to
incorporate our immediately adjacent urban corridor zones into a
High Wind Watch, which also extends into northern Weld County
where there is higher confidence in gusts exceeding the
comparatively lower high wind criteria of 58 mph. It`s doubtful
that a majority of lower elevations west of I-25 see such high
winds, but localized fingers are a much more distinct possibility.
Generally speaking, most areas will see gusts in the 30-50 mph
range outside of our mountains. Either way, will let the evening
shift make the ultimate decision with regard to our urban corridor
highlights. Winds should diminish in the evening for the
lowlands, and weaken below high wind criteria for higher
elevations closer to midnight Tuesday night. It`s also worth
noting that elevated fire weather conditions will be in place
across our northern plains owing to the gusty winds. Snowfall was
very limited in these locations with the recent system, so fuels
there are susceptible to fire spread.

Wind aside, we`re in store for a mild day Tuesday thanks to ample
compressional warming, pushing highs above 60F for a majority of
the plains. Only some persistent lenticular clouds could keep a
few foothills-adjacent locations from crossing that mark.
Additionally, we`ll have occasional light snow showers in our
northern mountains with low-level moisture remaining trapped below
~600mb. These will become steadier Tuesday night as moisture
deepens, with mostly 1-4" of accumulation possible through sunrise
Wednesday across our higher mountain elevations north of I-70.

&&

.LONG TERM /Wednesday through Monday/...
Issued at 257 PM MST Mon Dec 8 2025

Light snow showers will gradually end Wednesday/Wednesday night,
with an additional 2-5" of accumulation possible, mainly in the
Park Range. The main concern for the later half of the week,
however, is the potential for another high wind event Wednesday
night into Thursday morning:

Looking at 500 mb analysis, we are progged to generally be in the
right exit region of the jet streak Wednesday night, which will
promote subsidence aloft. There is good agreement between models
of cross-barrier flow between 50-60 kts, and surface pressure
gradients of 12-14 mb from Grand Junction to Denver. With these
ingredients, confidence is building that the Front Range could see
wind gusts up to 70 mph. Cross-sections and modeled soundings
indicate that winds could peak overnight Wednesday into early
Thursday morning, with the chance of the wind-prone areas along
the foothills and adjacent plains seeing gusts up to 50 mph. Won`t
be surprised if Will continue to monitor model trends for
evidence of stronger gust potential along the high county and
lower elevations (keeping an eye out for any indication of a
critical layer developing, a more stable layer at ridgetop, and
stronger pressure gradients).

With compressional heating, Thursday could be about 10-20 degrees
above normal across the plains. Exactly how warm we get will
depend on the strength and duration of the downsloping winds.
Ensemble runs have max temperatures between the high 50s to mid
60s.

Friday and into the weekend, we will see a drying trend across our
forecast area, as an upper level ridge continues to build over the
southwestern United States. There is a bit of uncertainty in
temperatures for Friday, as an arctic air mass dips into the
central and eastern part of our country. Ensemble solutions show a
large temperature spread for the plains, with max temperatures as
low as 30s-40s and as high as mid 50s. Most likely, our eastern
plains will receive the western edge of the arctic airmass and
will see high temperatures in the 40s while farther west will see
temperatures up to mid 50s. The NBM seems to have a good grasp on
this, so have opted to keep it as is for now. For the weekend,
temperatures should warm up to slightly above normal values as the
upper level ridge shifts over Colorado the weekend.

&&

.AVIATION /18Z TAFS through 18Z Wednesday/...
Issued at 1024 AM MST Tue Dec 9 2025

All terminals anticipated to remain under VFR conditions through
the TAF period, however there is potential for a brief window of
lower SCT bases near 015 for KDEN between 07-13Z tonight/early Wed
AM.

For winds, current gusty west winds are expected to hold fairly
steady for the next 3-5 hours, before gaining a more northerly
component later afternoon at KDEN/KAPA. A weak FROPA will bring a
northeasterly direction starting 04-06Z tonight, with winds
gradually veering towards southerly drainage flow closer to
sunrise. Breezy daytime NW winds are forecast to resurface Wed,
but should be notably weaker than today`s. Winds will remain more
consistently out of the W at KBJC, with frequent gusts exceeding
40 kts through at least mid afternoon today.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
High Wind Warning until midnight MST tonight for COZ033>035-038-
039-042.

&&

$$

UPDATE...Danielson
SHORT TERM...BRQ
LONG TERM...MAI
AVIATION...BRQ