896 
FXUS65 KBOU 261923
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
123 PM MDT Mon Oct 26 2026

.KEY MESSAGES...

- Areas of fog, some dense, across the plains and I-25 Corridor
  tonight into Tuesday morning.

- Warmer and mostly dry much of this week.

- Unsettled weather potentially returning late in the weekend and
  early next week, with a 20-30% chance of season's first snow in
  lower elevations toward Tuesday. 

&&

.DISCUSSION /Through Monday/...
Issued at 123 PM MDT Mon Oct 26 2026

The upper level trough that brought the overnight/early morning
rain and mountain snow is pushing well to our northeast, with 
drier and more subsident airmass building in behind it. However, 
abundant low level moisture remained in place east of the Front 
Range, with the stratus deck only slowly burning off. While we do
expect more clearing through the late afternoon hours, areas of 
low clouds and fog will redevelop tonight in the moist boundary 
layer. This will be a hybrid radiational/advection fog event, 
with contributions from a developing weak Denver Cyclone. The 
expected location of the cyclone developing near/south of metro 
Denver and pushing slowly northeast overnight into early Tuesday 
morning favors fog over the eastern and northern plains, but then 
also wrapping around the back side of the cyclone down the I-25 
Corridor into at least the northern suburbs by/shortly after 
midnight. There's a 50-60% chance it moves as far south as the 
southern Denver suburbs before daybreak. Given the hybrid event 
and relatively narrow T/Td spreads, we think some areas will 
experience dense fog. It's quite difficult to narrow the exact 
locations of thickest fog development, but something to watch for 
the overnight and early morning hours with potential for a Dense 
Fog Advisory. We'll continue to monitor through the evening and 
overnight. 

On Tuesday, we're not sure that we'll see the magnitude of 
warming we earlier anticipated. That's because of the morning 
stratus and fog, and lack of lee troughing. We've generally cut 
temperatures a few degrees across the lower elevations but still 
mostly lower to mid 60s for highs (but a 30-40% chance we only 
hit the mid to upper 50s over the eastern plains). What we are 
more certain about is that tomorrow will start a 3-4 day stretch 
of dry weather. 

That dry weather will be courtesy of drier and brisk west to 
southwest flow aloft. There will be warm advection and flat 
ridging by Thursday, which should support highs pushing to near 
70F across the plains and I-25 Corridor.

Ensembles are still showing a subtropical push or partial remnants
(or at least water vapor transport) of Tropical Storm Vance in 
the eastern tropical Pacific getting drawn up as early as Friday. 
However, the main impacts of this would very likely (>80%) chance 
stay to the east of our forecast area. We'll only have a slight 
chance of showers reaching the far eastern plains by late Friday. 

A larger trough along with a possible subtropical moisture
connection/jet off the central and eastern Pacific reaches the 
far southwest U.S. by late Saturday and Sunday. While that is 
fairly well agreed upon by ensemble systems, models diverge
significantly by the time we reach Sunday into early next week. 
Yes, there is general troughiness and storminess expected, but 
some models move the trough through as an open or even shearing 
wave, while others develop a deep closed low somewhere between the
Midwest and Colorado. It was interesting to note the EPS showed a
rather marked increase in precipitation and even snow potential 
as we head toward Tuesday of next week, while the GEFS showed no 
discernible trend. The EPS had close to 30% of the members 
showing snow for Denver and the plains, while GEFS supported much 
lower odds (10-20%). Some of these runs, of course, were much 
colder than the vast majority of the ensembles, as evidenced in 
the large temperature variations (25th-75th percentiles from highs
in the mid 40s to mid 60s for Monday and Tuesday, but full range 
of outcomes from highs in the upper 20s to lower 70s). Stay tuned 
for the latest trends and what could maybe, just maybe, be our 
first snowfall in the lower elevations should the deeper/slower 
solutions verify. 

&&

.AVIATION /18Z TAFS through 18Z Tuesday/...
Issued at 1215 PM MDT Mon Oct 26 2026

Current GOES-19 satellite imagery shows the stratus deck that
affected the sites this morning breaking up with the south metro
(KAPA) seeing the most improvements so far. Still, with the 
saturated ground from the overnight rainfall/mist and low-level 
moisture, clouds will have a difficult time fully scattering out 
this afternoon. Therefore, we expect a sct deck around 1500 ft AGL
to 3000 ft AGL through mid-afternoon, but some improvements look 
possible as we get to late in the afternoon. KAPA should have 
fewer clouds than the other two sites. Winds this afternoon will 
turn to the east and should remain under 12 kts.

Another night of fog is looking increasingly likely (>70%) at 
KDEN and KBJC with 50/50 odds at KAPA. BUFKIT and model soundings 
continue to point to saturated low levels with dewpoint 
depressions at or under 1 degree. A Denver Cyclone is progged to 
develop to the north of the three sites this evening and move off 
to the northeast. This would cause a westerly component to the 
wind at all three sites with light and vrb winds as we get into 
Tuesday morning. In turn, short-term guidance is in very strong 
agreement that fog could rapidly develop this evening as early as 
6-8z from north to south on the north/west side of the cyclone. 
The period of highest confidence at KDEN for visibility around 1/2
SM and IFR/LIFR restrictions is from 9z through about 14z. There 
is a ~30% chance that visibility could even drop as low as 1/4 SM 
with vv001 causing further restrictions. Generally, the same 
timing is expected for KBJC with only slightly higher 
visibility/ceilings than KDEN. At KAPA, winds could be a little 
more southerly (downslope), which would lower overall chances for 
impactful fog directly at the terminal. Otherwise, if winds do 
keep more of a westerly component, fog/low ceilings/lowered 
visibility are in play there as well.

The fog and low ceilings should start to lift by about 15z Tuesday,
but sct clouds around 1000 to 2000 ft AGL look to stick around 
for a few more hours. VFR conditions appear possible by 18-20z 
Tuesday afternoon as skies clear. Winds turn to the east for 
Tuesday afternoon before becoming vrb by the evening.

&&

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

&&

$$

DISCUSSION...20
AVIATION...MV