435
FXUS65 KBOU 200918
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
218 AM MST Sat Dec 20 2025

.KEY MESSAGES...

- Light to moderate snow in the mountains today, with hazardous
  road conditions expected along and north of I-70 through the
  mountains. A Winter Weather Advisory remains in effect through
  through midnight Sunday.

- Gusty winds will continue over the higher terrain today but
  speeds will be lighter than Friday.

- There could be a few hours of elevated fire conditions over the
  southern foothills and western portions of the Palmer Divide
  this afternoon. West to northwest winds up to 35 mph may occur.

- Warmer, drier pattern returns again for next week. Some hints
  of a more wintry pattern in the mountains in the latter half of
  the week?

&&

.UPDATE...
Issued at 207 AM MST Sat Dec 20 2025

Rather stg WNW flow aloft will remain over the area today and
tonight.  Cross-sections show moisture embedded in the flow across
nrn areas of the CWA.  This moisture combined with favorable
orographics will lead to periods of snow across the nrn mtns thru
early aftn followed by decreasing actitvity by late aftn.
Position of upper level jet may lead to some banded hevier snow in
some mtn areas. At lower elevations, a cold front will move
across the plains this morning and into the I-25 Corridor by mid
to late morning. This will lead to cooler temps for this aftn
across the plains. Meanwhile, position of upper level jet along
with some increase in low level moisture behind the front may
lead to a chc of showers at lower elevations. At this time it
appears best chc will be along and north of a Fort Collins to
Greeley line.

As far as winds, they will be lighter today, however will still see
gusty winds over the higher terrain thru this aftn and along
portions of the I-25 Corridor this morning before the front arrives.


UPDATE Issued at 933 PM MST Fri Dec 19 2025

The high wind threat has pretty much ended this evening and we
allowed the High Wind Warnings to expire. However, there will
still be gusty winds and they are currently spreading east across
most of the Denver metro area. Overall, peak gusts 35-50 mph
overnight seem on track per latest average guidance. And that will
be due to continued subsidence and strong winds aloft. Red Flag
Warnings will remain in effect til midnight, but we earlier
removed the Particularly Dangerous Situation Wording as winds have
subsided significantly.

Radar shows light snow starting up in the mountains, but I-70
mountain corridor will be on the lighter side given it`s too far
south of the main moisture plume, so we`ve cut back those amounts
a bit. However, far northern mountains are still on track to do
well, mainly in the Park Range north of Rabbit Ears Pass.

&&

.DISCUSSION /Through Friday/...
Issued at 339 PM MST Fri Dec 19 2025

Very little to add from what we`ve been discussing over the last
day or so. Did we see the high winds? Yes... with numerous gusts
between 85 and 100 mph observed across the lower half of the
foothills and adjacent plains in Boulder county. Across the rest
of the Red Flag Warning, we`ve seen gusts in the 50-80 mph range
with humidity values generally falling in the upper single digits
to upper teens. There have also been numerous reports of tree and
powerline damage, along with several plumes of blowing dust.

The general thought is that we are past the peak of the wind gusts
in our CWA. The mountain wave appears to be slowly contracting and
pushing back into the lower foothills, and should steadily weaken
through sunset. However, guidance is fairly insistent on pushing
some gusts (in the 35-50 mph range) into the I-25 corridor
overnight tonight while relative humidity values remain slow to
recover. Did make some adjustments to the wind and RH grids but
otherwise left things as they were. A weak cold front will bring
some relief later tonight into tomorrow morning.

Meanwhile, we can`t forget about the developing snow across the
mountains later tonight into tomorrow. Moisture depths and lapse
rates are modest, but we are in the vicinity of a 130kt jet
streak. We`ll likely see some banded snowfall and gusty winds
through most of the day tomorrow... and given some potential
travel impacts and the relative lack of snow so far this season a
Winter Weather Advisory still seems appropriate even if snowfall
totals aren`t terribly impressive.

The weather pattern should turn quieter by the end of the weekend
into next week as a ridge begins to build across the south central
CONUS. Drier southwesterly flow aloft should limit precipitation
chances, and warming mid-level temperatures will bring
temperatures back to well above normal temperatures. 60s to 70s
appear likely most days next week. Thankfully, the ridge appears
strong enough to displace the stronger mid/upper flow off to the
north. There are some hints of some better moisture returning to
the mountains sometime late next week, but details are hazy at
this point and frankly I don`t want to scare any moisture away
right now. We`ll keep an eye on any storm potential this weekend
into early next week.

&&

.AVIATION /06Z TAFS through 06Z Sunday/...
Issued at 1015 PM MST Fri Dec 19 2025

Still seeing decent mixing across the area with gusty W to WNW
winds at all sites.  Expect these gusty winds will continue
overnight before a cold front moves in after sunrise.  Gusts
from 50 to 60 mph will be possible at BJC with 35 to 40 mph
at DIA at times. APA will have some gusts up to 30 mph.

Should see a cold front move in between 14z to 15z with NE winds
developing for a few hours at APA and DIA. BJC will likely stay W
or WNW. Winds at DIA will turn move SE by 19z with APA becoming
NW. BJC will have WNW winds with a few gusts to 30 mph thru 23Z.

At this time, precip chances will likely stay to the north of the
TAF sites Sat morning with only some mid and high level cloud
cover as ceilings stay above 12000 ft.

&&

.FIRE WEATHER...
Issued at 215 AM MST Sat Dec 20 2025

Elevated fire conditions may develop by midday over the southern
foothills and across western portions of the Palmer Divide. Gusty
west to northwest winds up to 35 mph may occur but humidity levels
shoulld stay above 20 percent. The winds should decrease by late
afternoon.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until midnight MST tonight for COZ031-
033-034.

&&

$$

UPDATE...RPK
DISCUSSION...Hiris
AVIATION...RPK
FIRE WEATHER...RPK

NWS BOU Office Area Forecast Discussion