265
FXUS65 KBOU 011138
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
438 AM MST Mon Dec 1 2025

.KEY MESSAGES...

- Sunshine returns today, but tempered warming and still well
  below normal temperatures.

- Light snow showers return to mountains Tuesday, with high
  temperatures warming to near normal levels.

- Increasing confidence in more widespread snow late Tuesday night
  and Wednesday, including highest potential for lower elevation
  travel impacts so far this season.

&&

.UPDATE...
Issued at 225 AM MST Mon Dec 1 2025

Snow has exited all but the far southeast portions of the
forecast area in east central Colorado in these wee morning hours.
Skies were clearing rather quickly from the northwest, outside of
patchy low level stratus. Therefore, other than a couple patches
of morning fog/trapped clouds in high mountain valleys and in the
lower elevations of the South Platte and Cache La Poudre river
valleys, we`ll see plenty of sunshine today. Despite the return of
sun, high temperatures will still be nearly 10 degrees below
normal.

The remainder of the forecast remains largely unchanged since
yesterday, with a return of light snow showers in the northern
mountains Tuesday, and then more widespread measurable snow
(finally!) Tuesday night and Wednesday. There was a trend of
slightly faster arrival, with snow developing across the I-25
Corridor and adjacent plains late Tuesday night. Thus, the
Wednesday morning commute is shaping up to be slow and hazardous,
with lingering impacts potentially lasting into the pm commute.
Models were fairly consistent with the vast majority of ensembles
showing 1-4" snow amounts for the I-25 Corridor and nearby
adjacent plains, with the EC ensembles on the higher end and GEFS
generally on the lower end. Mountains would get a few inches more
while the far eastern plains could still be skunked.

&&

.DISCUSSION /Through Sunday/...
Issued at 1234 PM MST Sun Nov 30 2025

Snowfall has developed on schedule in our high country and will
continue to increase in the afternoon under a deepening moisture
column. Upstream observations so widespread precipitation across
the Western Slope, and we can expect travel conditions in our
mountains to deteriorate steadily in the coming hours as this
migrates eastward. The overall picture through tonight remains
relatively unchanged, with some banded snow showers expected to
spill into the urban corridor as early as 4-5pm, but mostly into
the evening hours. The better potential for these bands will be
roughly south of I-70 as described in previous discussions, owing
to the more favorable jet streak position aloft and deepest
moisture. Most of the lower elevations will receive less than 1",
but localized narrow corridors may accumulate 2 or even 3" under
the heaviest/most persistent bands, enough for some enhanced
travel impacts, and may extend into portions of our southern and
eastern plains. Snowfall aside, temperatures have been notably
slow to climb, with most of the lower elevations barely reaching
into the lower 20`s as of this writing. This trend will carry over
into the overnight period, with another cold night ahead bringing
lows into the single digits to low teens for most areas.

Tuesday`s warming will be modest as the trough axis pushes east,
and have trended highs downward slightly keeping temperatures
firmly in the 30`s across the plains/I-25 corridor, and 20`s for
most mountain communities. It will be an otherwise dry day past
sunrise, with a distinct lull in mountain snow and clearing skies
across the region.

Strengthening westerly flow ahead of a developing trough to our
west will reignite the potential for mountain snow showers on
Tuesday, with recent runs a little more bullish on accumulating
snow potential, particularly for the Park and Medicine Bow Ranges.
Amounts should nonetheless be rather minor given still limited
moisture.

Confidence in the arrival of another storm system on Wednesday has
continued to increase with the latest guidance, which favors a
shearing shortwave descending into AZ/NM before lifting NE into
the plains come Thursday. This path easily generates the highest
potential for winter weather travel impacts to the lower
elevations yet this season, even if questions remain regarding
accumulation amounts. There`s moderate consensus in a period of
modest northeasterly upslope flow during the day Wednesday, which
would promote quite high (~75-80%) precipitation probabilities for
our foothills, Denver metro and Palmer Divide in particular.
However, the system won`t lack speed, with its rapid eastward
motion being a limiting factor in snowfall potential. Ensemble QPF
spread appears quite unimodal and symmetric, generally favoring
0.1-0.3" of QPF for the mountains and I-25 corridor with a small
handful of both drier and wetter scenarios. Still time to trend
in either direction, of course.

As the low merges with the broader synoptic flow Thursday, we look
to return to a more progressive pattern with troughing to our
north and ridging in the vicinity of the West Coast. The nuances
in the pattern can`t yet be discerned, but the door will remain
open for the passage of a few shortwaves under northwest flow that
would sustain a few windows for predominantly mountain snowfall.
With the bulk of the troughing expect to remain to the north, our
northern mountains will be most favorably positioned for some
additional healthy snowfall during the latter half of the week.
This pattern also lends itself to more robust pressure gradient-
driven flow and hence stronger winds across the region.

&&

.AVIATION /12Z TAFS through 12Z Tuesday/...
Issued at 438 AM MST Mon Dec 1 2025

Sufficient drainage winds are developing, which will keep any
threat of fog north of KDEN and KBJC this morning. We do
anticipate winds becoming light and variable toward 17Z, before a
more northerly component develops. However, fog should have
dissipated by then so mostly clear skies on tap for the first half
of the TAF period, and then only some thickening high cirrus
clouds after about 03Z. Therefore, VFR conditions will persist
through the entire period.

There is some uncertainty to winds this afternoon as an
anticyclonic flow pattern is expected to develop due to northwest
winds coming across the Cheyenne Ridge. This would support an
earlier turn to east/southeast which could happen as early as 20Z,
and as late as 23Z. Then winds turn more south/southwest by 01Z and
persist around 10-12 kts through about 17Z-18Z Tuesday. KBJC will
have a 50-60% chance of mountain wave interaction with a few
gusts around 25 kts after 08Z tonight, so added a TEMPO for that.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

UPDATE...20
DISCUSSION...BRQ
AVIATION...20

NWS BOU Office Area Forecast Discussion