413
FXUS65 KBOU 200027
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
527 PM MST Fri Dec 19 2025

.KEY MESSAGES...

- Particularly Dangerous Situation Red Flag Warning remains in
  effect for the lower foothills of Larimer, Boulder, and
  Jefferson Counties, and the CO-93 corridor for high winds and
  low relative humidity... but conditions should slowly improve
  this afternoon.

- Watching how much wind continues into the evening and overnight
  hours across the Foothills and I-25 corridor.

- Light to moderate snow returns to the mountains Saturday, with
  deteriorating road conditions expected along and north of I-70
  through the mountains. A winter weather advisory is in effect
  from midnight tonight through midnight Sunday.

- 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?

&&

.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 /00Z TAFS through 00Z Sunday/...
Issued at 525 PM MST Fri Dec 19 2025

Most models are not showing normal drainage wind patterns at DIA
overnight. Most are continuing to show some west-northwesterly
downsloping much of the night.  However forecast speeds overnight
have decreased on most of the them. The latest high resolution
models continue to have poor initialization. At this time, will
go with some scaled down west-northwesterly overnight at DIA.
The progged low level pressure gradient does favor downsloping of
some sort. Models have normal diurnal wind patterns for DIA on
Saturday and Saturday night. There will be no ceiling issues.

&&

.FIRE WEATHER...
Issued at 339 PM MST Fri Dec 19 2025

No changes to the current Red Flag Warnings at this time. There`s
still some pockets where wind gusts are in the 60-80 mph range and
relative humidity is still near 10 percent. Wind gusts are weaker
in most other locations and we should see gradual improvement this
evening into the overnight hours. There is some potential for
brief re-enhancement of the winds along the base of the foothills
this evening, along with fairly widespread 30-50 mph across the
rest of the Red Flag Warning area. We should see better moisture
overnight as temperatures begin to cool and a weak cold front
brings some slightly better moisture back into the area after
midnight.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from midnight tonight to midnight MST
Saturday night for COZ031-033-034.

High Wind Warning until 8 PM MST this evening for COZ035-036-038-
039.

Red Flag Warning until midnight MST tonight for COZ215-216-
238>243.

&&

$$

DISCUSSION...Hiris
AVIATION...66
FIRE WEATHER...Hiris

NWS BOU Office Area Forecast Discussion