860
FXUS65 KBOU 310547
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1147 PM MDT Fri Oct 30 2026

.KEY MESSAGES...

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

- Mild and mostly dry through Saturday.

- 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 /06Z TAFS through 06Z Sunday/...
Issued at 1123 PM MDT Fri Oct 30 2026

The main impacts for the TAF period continue to be with fog
development and low stratus across the airfields tonight through
late Saturday morning, dropping conditions down to LIFR by early
Saturday morning. While guidance continues to portray this
outcome, there has been some back-and-forth with timing over the
past several model runs. At this time, dewpoint depressions range
from ~2-3F at and just north of KDEN`s airfield. There has
already been a brief period of BR and visibility dropping to 6SM
when winds had less of the current SSW component. As such, as long
as the southerly winds can hold on, there should be enough
downslope warming/drying to keep stratus and fog from developing.
We do expect winds to become light and variable by around 9Z that
would allow for temperatures to cool just enough to see BR return
and fog to start to advect southward from the north. The best
timing for LIFR conditions looks to be between 12Z-16Z, with
conditions starting to improve between 17Z-18Z, returning to VFR
by around 20Z. There are some uncertainties with timing at KBJC,
as the latest guidance has pushed it back by a few hours, and with
larger dewpoint depressions (between 4-6F) currently in place
here, it would take slightly longer to get going there. With BR
and 6SM currently observed at both KLMO and KEIK, this would
change quickly with any northern component to bring it southward,
which is expected around 8Z. Potential still remains uncertain at
KAPA since the last TAF package, that has kept TEMPOs in place vs
any prevailing fog for this update, but the best timing does still
look to be between 13Z-16Z if it makes it that far south. Light
northerly winds are still anticipated by late Saturday morning,
becoming NE for the afternoon, and turning to the south for the
overnight hours.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory from 3 AM to 10 AM MDT Saturday for
COZ038>040-042-043.

Dense Fog Advisory until 10 AM MDT Saturday for COZ046-047.

Dense Fog Advisory until 10 AM MDT Saturday for COZ050-051.

&&

$$

DISCUSSION...RPK
AVIATION...9

NWS BOU Office Area Forecast Discussion