598
FXUS65 KBOU 011943
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1243 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 /18Z TAFS through 18Z Monday/...
Issued at 1120 AM MST Sun Nov 1 2026

Current webcams and observations still show a couple stubborn fog
banks over the northern portions of the Denver metro. However, the
developing southerly wind speeds (10-14KT) will help dissipate the
fog, as well as push it north and away from KDEN. KBJC could still
see brief reductions in ceilings and visibilities in the next hour
or so as fog banks linger in the vicinity given the very light
(<05KT) NNW winds in place.

We expect steady southerly winds with occasional gusts up to 25KT to
develop over the eastern plains by 19-20Z, with a sharp drop in
speeds or boundary positioned diagonally over Denver, likely along I-
76. As this boundary wobbles north and south, temporary shifts to a
light northwest wind could be observed at KDEN, with a lower
probability (30% chance) at KAPA. A light northwest wind will
prevail at KBJC and areas northwest of this boundary. Model
guidance suggests a period of light showers this evening, between
00Z and 04Z, so we have included PROB30s at all three airports in
this TAF.

A strong cold frontal passage is expected tomorrow morning between
14Z and 16Z, bringing breezy northerly winds with it and behind it.
We expect the strongest wind gusts (30-40KT) to occur mid afternoon,
with the strongest wind speeds likely at KDEN and east, over the CO
plains. A TEMPO group for stronger gusts may be warranted in the
next TAF if guidance continues to trend towards the windier
solutions. In terms of rain chances, we expect light showers
scattered throughout the area for most of the day behind the front ,
although the best timing for showers over the terminals remains
uncertain at this time.

&&

.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...AA