865
FXUS65 KBOU 301830
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1130 AM MST Sun Nov 30 2025

.KEY MESSAGES...

- Another round of light to moderate snow for the mountains today
  and tonight. Areas of light snow/flurries spreading onto the
  plains late this afternoon and evening, but a couple narrow
  bands of briefly heavier snow possible.

- Coldest air of the season will stick around through Monday
  morning.

- Slight moderation of temperatures Monday through Tuesday. Then
  another potential shot at wintry precipitation Wednesday into
  Thursday.

&&

.UPDATE...
Issued at 320 AM MST Sun Nov 30 2025

Satellite shows a rather vigorous shortwave moving southeast across
southern Idaho in these early morning hours. At the same time, a
mid and high level cloud deck was developing and spreading east
across the forecast area. While this disturbance is relatively
moisture starved in the low levels, it does have persistent and
modest QG lift associated with it, and a couple mesoscale features
should aid snow production as we head through the day and this
evening.

For the mountains: As the disturbance moves closer, snow is still
on track to develop this morning. This occurs as QG lift
increases and combines with orographic forcing - although not
terribly favorable west/southwest flow. However, that snow will
become widespread and more intense through the afternoon as lift,
orographics, and moisture profiles/depth improve. A rather
vigorous upper level speed max will also round the base of the
trough late this afternoon and evening. At the same time, mid
level frontogenesis will develop across the forecast area. The
combination of these and rather unstable mid levels would support
development of a few heavier bands of precipitation, with the I-70
Mountain Corridor and points south favored. We see most mountain
areas getting 3-6", but up to 8" or so in the heavier bands and
favored orographic locations. The Winter Weather Advisory will
remain in effect from 11 am today to 5 am Monday.

For the plains: That mesoscale forcing discussed above would also
support higher chances of snow, despite the lack of any frontal
push or meaningful upslope. Again, given the position of the left
exit region of the upper level speed max and F-gen, the I-70
Corridor and points south would be favored most for seeing locally
heavy but narrow bands of snow. At this time, those should be
rather brief but something to watch as a couple bands would
support at least an inch or two of accumulation and more
meaningful travel impacts. So, while deterministic forecasts
remain light and under an inch for the plains and I-25 Corridor,
don`t be surprised to see a couple 2+" amounts given the
ingredients mentioned above. We`ve increased PoPs and our
probabilistic (90th percentile) snow forecasts in those areas
accordingly.

Snow is on track to taper off after midnight tonight as weak
subsidence and drying arrives from the northwest. Cold air
remains, with highs only in the 20s for the plains today due to
a cold start and thickening clouds. Lows tonight likely to drop
into the single digits to lower teens again.

For the rest of the forecast cycle...no significant changes were
noted. However, there was a continued gradual uptick in snow
forecasts for the mountains and I-25 Corridor for the next
disturbance slated in by Wednesday.

&&

.SHORT TERM /Through Sunday Night/...
Issued at 205 PM MST Sat Nov 29 2025

The shortwave responsible for Denver`s first official snowfall of
the year (an exciting 0.2") has raced into the Midwest, leaving
most of Colorado in a cold but dry airmass. Temperatures this
afternoon have remained in the mid 20s to low 30s, and won`t warm
much further over the next hour or two. Meanwhile, the strong wind
gusts over the northeast plains have gradually diminished over the
past couple hours and should continue to weaken as the stronger
mid-level flow shifts off to the east.

We`ll be left with a fairly quiet night tonight, with high cloud
cover gradually spreading across the area in advance of the next
quick moving storm system. Overnight lows should drop into the
single digits for many locations, but may be dependent on how
quickly cloud cover spreads back in. With the cold airmass
remaining overhead, daytime highs on Sunday will again stall out
in the 20s to 30s across most of the forecast area.

The next shortwave is expected to swing from its current position
in Washington down into the Four Corners region by Sunday night,
before quickly ejecting into the central Great Plains on Monday.
While the best QG ascent is short lived and a little to the
south/west of our forecast area, there`s enough moisture for
orographic snow showers across the mountains. There may be a
period of enhanced snow rates during the evening hours, aided by a
favorable upper jet streak position and mid-level frontogenesis.
This would also favor a band or two of snow making it into the
I-25 corridor and plains, though accumulations would be fairly
limited. Unlike this past event, guidance does actually produce
some modest QPF/snow as far east as I-25, and at least a few spots
might see up to an inch or so of snow across the Denver metro.
Totals in the mountains will generally be similar to this previous
event, with generally 4-10" of snow expected on favored slopes.

&&

.LONG TERM /Monday through Saturday/...
Issued at 205 PM MST Sat Nov 29 2025

With the trough rapidly exiting to the east Monday, temperatures
will manage to climb slightly above freezing, although a brisk
northerly wind during the daytime hours will keep it feeling rather
cold despite the breaking cloud cover.

Flow aloft will begin backing to a more westerly direction by
Tuesday in response to a developing shortwave over the Northern
Rockies. We`ll see gradual deepening of moisture over the high
country through the day which will allow for some light orographic
snow showers, especially for our more northern mountains,
although any potential travel impacts would more likely hold off
until the overnight period or Wednesday. Guidance indicates the
core of the shortwave shearing off to the SW and becoming a
cutoff low, with a still substantial variance in its positioning
and progression. Generally, the latest ensemble guidance appears
slightly more favorable for a period of relatively shallow upslope
flow on the urban corridor side for Wednesday, supported by the
increase in members showing some snow accumulations for the lower
elevations. Around 1/4 of members produce ~0.20" or more for parts
of the I-25 corridor and plains, indicating at least a higher
potential for travel impacts to these areas compared to this
weekend`s weaker clipper systems. It`s far from unanimous however,
with placement and track of the cutoff low being the primary
factor to watch. Per usual, confidence in travel impacts is
slightly higher for our mountainous areas on Wednesday.
Regardless, temperatures look to regress closer to the freezing
mark after Tuesday`s modest warmup.

Model agreement increases considerably past Wednesday. Generally
speaking, ensembles favor continued troughing over the northern
CONUS/Canada with ridging closer to the West Coast. This leaves the
door open for the passage of a few shortwaves through the northern
plains and/or Rockies, but there`s little clarity as to their
frequency or track. It`s a pattern that would lend greater
confidence to the potential for windier conditions across the region
for the latter half of the week along with some moderation in
temperatures, with the precipitation component carrying more
uncertainty.

&&

.AVIATION /18Z TAFS through 18Z Monday/...
Issued at 1041 AM MST Sun Nov 30 2025

Clouds have thickened ahead of schedule this morning, with even a
few snowflakes already observed at KDEN over the past hour or so.
Light winds remain in place across the TAF sites and are still on
track to see a transition to the southeast this afternoon as a
surface cyclone becomes more pronounced. Current SSW winds at KDEN
may become more variable before the SE winds prevail between
18-20Z. The same is expected at KAPA. Winds at KBJC are expected
to see a N to NW transition through the afternoon.

A few changes were made to the TAFs this morning as guidance
suggests slightly lower visiblities dropping to as low as 1SM
early this evening, when snow moves from west to east across the
TAF sites, beginning first at KBJC between 22-23Z, followed by
KDEN and KAPA shortly thereafter. Generally light snow
accumulations are expected across the TAF sites, though the
ingredients will be in place to see potential for snow band
development between the 0-6Z time frame that could bring some
localized heavier amounts (up to 2 inches; KAPA:20-25%, KBJC:20%,
KDEN:15% chance).

While some slight clearing is currently occurring with regards to
ceilings, these should gradually begin lowering again around 20Z,
with MVFR conditions expected through the overnight hours, with
some brief periods of IFR conditions possible. Should see clearing
conditions early Monday morning (13-15Z) when winds turn towards
the WSW. Expecting another gradual shift towards the N to NNE for
KDEN/KAPA through the afternoon, with KBJC holding onto WSW winds
through the day.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 5 AM MST Monday for COZ031-033-034.

&&

$$

UPDATE...20
SHORT TERM...Hiris
LONG TERM...BRQ
AVIATION...9

NWS BOU Office Area Forecast Discussion