563
FXUS65 KBOU 311802
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1202 PM MDT Sat Oct 31 2026

.KEY MESSAGES...

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

- Mild and mostly dry today.

- Unsettled weather returns late Sunday and Monday.Mountain snow
  is likely (>70% chance) above 8500ft during thistime. High
  uncertainty remains for the foothills and plains.

&&

.DISCUSSION /Through Friday/...
Issued at 1145 PM MDT Fri Oct 30 2026

Once again will be dealing with areas of dense later tonight thru
Sat morning over portions of the plains and I-25 Corridor. Timing of
its development, closer to nrn areas of the I-25 Corridor and over
Weld county, is still a bit uncertain.  However, believe it will
begin developing around 09z and then spread south into the Denver
Metro by 11z or so.  Fog will likely last thru 16z and then
gradually lift in most areas.

Meanwhile, for the rest of Sat, a disturbance embedded in SW flow
aloft will move across the higher terrain by midday.  This feature
will bring a chc of showers to portions of the higher terrain as it
moves across.  Over the plains, expect mainly dry conditions with
highs in the mid 50`s to lower 60`s.

Looking ahead to Sun, the ECMWF and GFS have an elongated upper
level trough moving into the nrn Rockies and Great Basin by late Sun
aftn. Ahead of this feature, rather stg SSW flow aloft will be over
the area with an influx of subtropical moisture.  For most of the
day, the best chc of precip will stay to the west but by late aftn
should see an increasing chc of showers over the higher terrain.
Across the plains, sfc low pres will extend from ern WY into ern CO
with gusty southerly winds by aftn.

For Sun night into Mon, the elongated upper level trough will move
eastward with a couple pieces of energy associated with it. One
piece of energy will move into the Dakota`s while the 2nd piece of
energy tracks across srn CO/nrn NM.  As the main upper level trough
and associated QG ascent moves across will see rain and snow over
the higher terrain Sun night into Mon.  Over nern CO, a cold front
will move across Mon morning with gusty NNW winds behind it. QG
fields still show favorable mid level ascent across the plains thru
the aftn so will keep in a good chc of showers over the plains.
However, the downslope NNW winds may reduce precip chances closer to
the I-25 Corridor.

By Mon night, the main upper level trough will move east of the area
with drier air moving in behind the system.  Will continue to see a
good chc of showers Mon evening mainly over the east central plains.
However, by late Mon evening should see precip gradually end.

On Tue, an upper level ridge will begin to build into the area with
dry conditions and near seasonal temperatures.  Looking ahead to the
middle part of next week, there is considerable uncertainty as to
whether another system will affect the area or not.  The latest GFS
tracks this system across the nrn Rockies while the ECMWF has it
moving across Colorado.

&&

.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...RPK
AVIATION...BM