015
FXUS65 KBOU 301140
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
540 AM MDT Fri Oct 30 2026

.KEY MESSAGES...

- Areas of dense fog across portions of the plains through mid
  morning Friday. This fog will impact the morning commute from
  Denver north along I-25, northeast along I-76, and east along
  portions of I-70. More fog will be possible Friday night into
  Saturday morning.

- Mild and mostly dry to end the 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 /12Z TAFS through 12Z Saturday/...
Issued at 532 AM MDT Fri Oct 30 2026

Fog will be the main impact during the TAF period. Steady LIFR
conditions developed at DEN just prior to 09z and should continue
through about 15z before the fog burns off.

A bit more of question mark at BJC and APA. BJC has remained on
the edge of the fog bank for the last couple of hours, shown well
by the FAA WeatherCam and surrounding webcams/surface
observations. At APA, fog has started to creep towards the
southeast metro, with BKF recently dropping to 1/2SM. Guidance
still insists that fog will push further south over the next
couple of hours, meaning that BJC should see more consistent 1/4SM
visby soon... though it`s appears unlikely to reach APA at this
time.

Once fog burns off, light east/northeast winds are likely at the
terminals through most of the day with VFR conditions prevailing.
Weak drainage is expected again for tonight into Saturday morning.
Both the HRRR and RRFS support another batch of dense fog for
BJC/DEN, but favor slower development compared to today. Have kept
just the VCFG in for now but may eventually need to introduce some
LIFR, focused around the 12-15z window Saturday.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 10 AM MDT this morning for COZ038>040-
042>044.

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

&&

$$

DISCUSSION...RPK
AVIATION...Hiris

NWS BOU Office Area Forecast Discussion