352
FXUS65 KBOU 012354
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
454 PM MST Sun Nov 1 2026

.KEY MESSAGES...

- Snow increasing overnight and Monday morning over the
  mountains.

- Snow level falls to 8,000 to 8,500 feet Monday morning.

- Mountain roads will become slippery in spots, especially
  through mountain passes.

- Scattered to numerous rain showers and cooler temperatures for
  the plains on Monday. A few snowflakes possible for the Palmer
  Divide on Monday night.

&&

.DISCUSSION /Through Sunday/...
Issued at 1243 PM MST Sun Nov 1 2026

Water vapor satellite imagery shows an upper level trough
centered over California and Nevada with a very moist southwest
flow aloft ahead of it (atmospheric river). Within this southwest
flow aloft there is a shortwave trough embedded over the Desert
Southwest. Widespread rain and mountain snow will continue across
western Colorado, possibly bringing historic flooding to southwest
Colorado. For our forecast area, north central and northeast
Colorado will be rain shadowed, and any precipitation is expected
to be light under the moist southwest flow aloft. The best chance
for rain and high mountain snow will be late this afternoon and
evening as the shortwave trough races northeast across Colorado.
The airmass remains warm tonight while southwest flow aloft
continues. The snow level stays above 10,000 feet most of the
night before it begins to fall towards sunrise as the upper level
trough nears.

The upper level trough axis will be centered over Colorado at 12Z
Monday. As it progresses eastward it will be over the eastern
Colorado border by 00Z Tuesday. The best lift associated with the
upper level trough will be Monday morning and into the early
afternoon. There is still a good amount of uncertainty regarding
rainfall amounts along the Front Range and eastern plains. Expect
a period of low level flow (below 700mb) where winds are north to
northeast, this should be a favorable period for rainfall. Once
flow turns to a downslope northwesterly direction rain should
quickly end. Timing of this transition is where the forecast
uncertainty lies. Ensemble means are around a quarter to a third
inch for precipitation amounts for the Front Range and plains, but
individual members vary from over a half inch to less than a
tenth inch. For the mountains, snow increases around 12Z as lift
from the upper level moves in. The snow will continue as flow
turns northwesterly, providing orographic lift. Drier air slowly
filters into the mountains after midnight Monday night. The snow
level quickly falls to 8,000 to 8,500 feet Monday morning as
colder air accompanies the upper level low. As far as snow totals
go, expect 3 to 10 inches for the mountains, heaviest across the
northern mountains. A Winter Weather Advisory has been issued for
this. For the northeast plains, winds increase Monday, becoming
very windy Monday afternoon and Monday night as a surface low
deepens over the Central Plains. Gusts to 55 mph will be possible
and a few gusts above 60 mph can`t be ruled out in the typical
windy areas over the plains.

On Tuesday, a few light rain showers will be possible over the
plains early in the morning. Overall, dry conditions and near
normal temperatures are expected for Tuesday as an upper level
ridge builds over the region. The ridging doesn`t last long, as a
quick-moving, small, closed low displaces the ridge by early
Wednesday. This low moves across Colorado Wednesday, bringing an
area rain and mountain snow. Not a lot of moisture with this
system, so precipitation amounts are on track to be light.

On Thursday and Friday a disorganized weak westerly flow aloft
will be over the western halfof the country. Colorado will stay
between a shortwave trough passing south over the Southern Rockies
and another one to our north that will travel across the Northern
Rockies. This will leave us with dry conditions and near normal
temperatures. For next weekend, models generally favor ridging
across the intermountain west. If this prevails, we`ll see dry
conditions continue with near normal to above normal temperatures.
Some ECMWF ensemble members show a shortwave trough digging south
along the backside of the ridge and could graze Colorado. So there
is a small chance (~10-20%) we could see cooler temperatures and
light precipitation if this system happens to pan out.

&&

.AVIATION /00Z TAFS through 00Z Tuesday/...
Issued at 454 PM MST Sun Nov 1 2026

Denver Convergence Zone had shifted south of KDEN earlier this
afternoon, and modest agreement it will stay south so we`ve opted
for prevailing W-NW winds on the back side of this feature.
However, showers developing in the area could disrupt this in the
short term through 03Z with VRB winds. Cigs will also drop
sufficiently for IMC with these early showers. After that, there
should be a break in the showers and higher ceilings overnight.
However, there is a small threat that some prefrontal fog may
develop, enough to go with VCFG 10Z-15Z.

A strong cold frontal passage is expected tomorrow morning between
14Z and 16Z, bringing gusty northerly winds to 30-35 kts through
the rest of the TAF period at KDEN, with gusts generally 20-28 kts
at KBJC and KAPA. With the front and a second round of synoptic
scale lift arriving, we have enough confidence for TEMPO -SHRA
15Z-19Z, potentially lingering through the afternoon with another
round of -SHRA in the evening. Also, we expect enough moistening
and northerly flow under the trough for mostly IMC conditions in
the post-frontal airmass, and TEMPO MVFR ceilings.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 3 AM Monday to midnight MST Monday
night for COZ031-033.

Winter Weather Advisory from 5 AM Monday to midnight MST Monday
night for COZ034.

&&

$$

DISCUSSION...BM
AVIATION...20

NWS BOU Office Area Forecast Discussion