653
FXUS65 KBOU 300554
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1154 PM MDT Thu Oct 29 2026

.KEY MESSAGES...

- Areas of dense fog across portions of the plains overnight
  through mid morning Friday. This fog will impact the morning
  commute from Denver north to the Wyoming border

- Mild and mostly dry through the work week.

- Unsettled weather returns late this weekend and early next week.
  Mountain snow is likely (>70% chance) above 8500ft during this
  time. High uncertainty remains for the foothills and plains.

&&

.DISCUSSION /Through Thursday/...
Issued at 1026 PM MDT Thu Oct 29 2026

For late tonight thru Fri morning main concern is how widespread
dense fog may become along portions of the I-25 Corridor from
Denver north to the Wyoming border and points eastward. HRRR has
been consistent in showing fog developing over ern Larimer and
Weld county by midnight and then spreading it southward into nrn
portions of the Denver area by 3 am or 4 am. This fog would then
linger thru the mid morning hours on Fri before lifting. In
addition, soundings show some potential for drizzle as well.

Meanwhile, for the rest of Fri, the flow aloft will be SW with
only isold showers possible in the mtns and far nern plains in the
aftn. As for highs, readings will be in the lower to mid 60`s
across the plains, however, lingering low clouds could keep temps
in the 50`s over the far nern plains.

For Sat, little change is expected as SW flow aloft remains over the
area. There still appears to be a weak disturbance embedded in
the flow which may bring a chc of showers to portions of the
higher terrain with an isold shower threat across the plains.
Temperatures will remain in the upper 50`s to mid 60`s over nern
CO.

Looking ahead to Sun and Sun night, there continues to be some
uncertainty as to how an upper level trough along the West Coast
evolves.  The ECMWF and GFS now have a disorganized elongated upper
level trough moving into the nrn Rockies and Great Basin by Sun
night.  Ahead of this feature, there will be quite a bit of
subtropical moisture affecting the higher terrain, especially by Sun
night.  As a result, should see an increasing chc of showers over
the higher terrain with snow levels dropping below 10000 ft late Sun
night.  Across the plains, it looks dry and windy thru Sun aftn as
sfc low pres intensifies from ern WY into ern CO.  By Sun night,
latest data shows varying precip chances across the plains.
For now, have kept in a chc of showers as a band of mid level QG
ascent moves across overnight.

On Mon, the ECMWF and GFS have two main areas of energy associated
with the elongated upper level trough.  One piece stays over the nrn
Rockies while a 2nd piece of energy moves across srn CO/nrn NM.  If
this occurs best chc of decent precip would stay mainly to the north
and south of the area.  Meanwhile, both models shows a stg cold
front moving across the plains with gusty north winds behind it.

For Mon night into Tue, the ECMWF and GFS keep the two pieces of
energy separated as the one piece over the nrn Rockies moves SSE
across Colorado while the other piece of energy moves from nern NM
into central Oklahoma. In addition, the GFS intensifies the upper
level low as it moves into Oklahoma by late Mon night. The ECMWF
has very little additional precip Mon night into Tue as much drier
air spreads across the area. Meanwhile, the GFS has a band of
precip over the ern plains Mon night but also decreases the chc of
precip over the area on Tue. Winds will remain gusty over the
plains Mon night into early Tue as well.

By Wed an upper level ridge will build over the area ahead of
another possible system moving across on Thu. For now, Wed looks
dry and warmer ahead of the next system.

&&

.AVIATION /06Z TAFS through 06Z Saturday/...
Issued at 1139 PM MDT Thu Oct 29 2026

Main concern for the TAF period continues to be the potential for
FG and LIFR conditions at DEN/BJC through mid-morning Friday.

There`s been a gradual increase in fog and stratus in
northern/northeastern Colorado over the past few hours, though
it`s difficult to determine the extent given the expansive high
cloud cover across the region. A weak surface cyclone exists,
centered roughly between DEN and FMM at this time. Surface dew
point depressions are still fairly large (6F at DEN but >10F at
LMO/BDU/BJC/CFO) to the west and southwest of the cyclone.
Cooler/moist air is evident in the northern I-25 corridor but it
should take a few hours until it pushes towards the terminals.

Most near term guidance is still insistent that lower visby should
arrive by ~10z tonight, with the best chance of LIFR FG between
11-15z. It looks unlikely that any fog or mist would make it to
APA, and it`s possible the edge of the fog bank sits just to the
north of BJC/DEN. We`ll continue to monitor trends overnight.

Any fog should quickly start to dissipate after 15z Friday
morning, with light east/northeasterly winds developing. Various
amounts of mid/high cloud cover should persist through the day
into Friday night, but VFR conditions are anticipated. There is a
slight chance of more fog Friday night into Saturday morning, but
I would like to see how the early morning fog evolves before
introducing anything at the end of the current TAF period.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 10 AM MDT Friday for COZ038-042-043.

Dense Fog Advisory from 3 AM to 10 AM MDT Friday for COZ039-040-
044.

Dense Fog Advisory until 8 AM MDT Friday for COZ046-047.

&&

$$

DISCUSSION...RPK
AVIATION...Hiris

NWS BOU Office Area Forecast Discussion