668
FXUS65 KBOU 312114
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
314 PM MDT Sat Oct 31 2026

.KEY MESSAGES...

- Areas of fog again late tonight through Sunday morning across
  portions of northeast and eastern Colorado.

- Unsettled weather returns late Sunday and Monday.Mountain snow
  is likely (>70% chance) above 8500ft during thistime, with a
  few inches of snow expected.

- Scattered rain showers for the plains on Monday.

&&

.DISCUSSION /Through Saturday/...
Issued at 308 PM MDT Sat Oct 31 2026

A blanket of fog over most of the I-25 corridor and parts of the
eastern Colorado plains made for ominous conditions to start the
day. In fact, satellite still showed a stubborn patch of mist and
low level clouds over Denver International Airport and its
surroundings just under one hour ago. Despite the passage of a
very weak shortwave over the area this afternoon, we expect mostly
sunny skies east of Continental Divide with high clouds moving in
late in the day. Southwest flow aloft will begin to transport
Pacific moisture towards the Four Corners this afternoon, which
will promote some isolated rain/snow showers over the high
terrain. Areas of fog will be possible once again tonight,
developing over the eastern plains first and slowly making its way
west to the Denver metro and I-25 corridor by dawn. However, we
expect the bulk of the fog to remain north of I-70.

The pattern turns more active tomorrow as a closed-low off the
Pacific Northwest coast and longwave trough extending south to Baja
California briefly split up and then merge again as both features
move east over the Great Basin. A subtropical jet will also slide
north over the Four Corners with the broad wave, bringing
precipitable water (PW) values that are 4-5 standard deviations
above climatology for the time of year (0.60-1.00"). However, with
such limited lift and instability, this plume of moisture may only
amount to light rain over the plains and Denver metro, with a trace
up to a few hundredths at most. Lee cyclogenesis east of Denver
will bring breezy southerly winds with gusts up to 30 mph for
portions of the east Colorado plains and Palmer Divide. Winds
should remain light for areas west of I-76. More widespread
stratiform rain is expected over the mountains, particularly
Sunday evening during the peak of moisture transport. In terms of
snow, snow levels looks to be too high for impacts during the day
with only light accumulations possible above 11,500ft. Snow levels
will begin to lower late Sunday night as the center of the cutoff
low drifts closer to the area.

A strong cold front will push through northern Colorado late Monday
morning, leading to a slight drop in temperatures over the plains.
The primary concern with this front will be the strong northerly
winds that will develop on the backside, potentially reaching speeds
up to 25-30 mph, and isolated gusts up to 55 mph over parts of the
east Colorado plains. Light intermittent rain will be possible
across the low elevations, with temperatures struggling to rise
above the mid 50s. For the mountains, snow levels will continue to
drop, likely reaching the 8,500-9,000ft level by late afternoon on
Monday, and continuing to drop overnight into Tuesday. Snow
accumulations will range between 2 and 5 inches, with the highest
amounts above 10,000ft. This will lead to periods of slick roads
and hazardous travel conditions late Monday afternoon through
Tuesday morning. Although snow amounts are just shy of Winter
Weather Advisory criteria at this time, an advisory may be
considered in the next forecast package for parts of the northern
mountains if model guidance trends any wetter. Snow levels may
drop as low as 6,500- 7,000ft by Tuesday morning. If enough
moisture lingers into Tuesday morning, a few flurries to a light
dusting of snow cannot be ruled out over the crest of the Palmer
Divide.

Looking ahead, temperatures will remain near normal to slightly
below normal for the rest of the work week with a period of quieter
weather expected as an upper level ridge forms over our region.
However, long-range ensemble means do hint at another period of
active weather and mountain snow chances for next weekend.


&&

.AVIATION /18Z TAFS through 18Z Sunday/...
Issued at 1202 PM MDT Sat Oct 31 2026

Light northerly winds, high clouds, and poor mixing have made it
difficult for the fog to dissipate. The higher clouds are
movingoff and visibilities are finally improving. We expect haze
to persist through the day due to limited mixing with restricted
visibilities below 6SM through 20Z to 21Z. Light north to
northeast winds continue today and then turn southerly tonight. If
southerly winds persist through tonight and Sunday morning, fog
should not form. However, a Denver cyclone is expected to form and
a wind shift to the northwest will be possible for DEN. If this
occurs, fog will very likely roll in. Added tempo for fog to the
TAF for Sunday morning. A shortwave trough lifts across the area
late Sunday morning, helping to break up the fog and possibly
bring light rain showers. By 18Z Sunday the shortwave is expected
to be northeast of the area with gusty south winds prevailing.

&&

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

&&

$$

DISCUSSION...AA
AVIATION...BM

NWS BOU Office Area Forecast Discussion