846
FXUS65 KBOU 130043
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
643 PM MDT Mon Oct 12 2026

.KEY MESSAGES...

- Change in the weather to cool, wet conditions is still on track.

- Showers will become more numerous in and near the mountains late
  Tuesday and Tuesday night, but then more widespread rain and
  mountain snow still on schedule for Wednesday - Wednesday night,
  before winding down Thursday.

- Several inches of snow expected for the mountains above
  9,500-10,000 feet with some travel impacts late Wednesday -
  Thursday morning. Lighter snow and at least a dusting into the
  mountain valleys and higher foothills.

- Drier and warmer again for next weekend.

&&

.DISCUSSION /Through Monday/...
Issued at 210 PM MDT Mon Oct 12 2026

A cold front will ooze southward across northeast Colorado
tonight, ushering in the first wave of much cooler temperatures
that will become increasingly chilly through Wednesday.
Precipitation chances will also be increasing through Wednesday
and Wednesday night, most likely bringing a light to moderate
rainfall for most of the lower elevations, and accumulating snow
and the season`s first travel impacts for the higher mountains.

For tonight and Tuesday, the main shower chances will remain over
the mountains with the greatest chances closer to the upper level
low spinning over the Great Basin. The majority of these should
impact the far western mountains (in Jackson and Grand Counties)
being near the upper level jet and deeper moisture plume. There is
a 30% chance that a few showers could spill across the northern
foothills as one speed max ejects out of that trough axis late
tonight/early Tuesday morning. On the plains, mostly dry conditions
will prevail but low clouds will overspread most of the plains
behind tonight`s cold front. While low clouds are expected to
slowly burn off/lift on Tuesday, we`ll be entrenched in the cooler
low level airmass. We`ve knocked a couple more degrees off our
forecast high temperatures and more in line with the cooler
guidance, with upper 50s to mid 60s expected over most of the
plains (coolest over the far north/east).

For Tuesday night and Wednesday, the upper level low in the Great
Basin will start to eject slowly eastward toward the Four Corners
region. This means increasing upper level support and QG forcing.
However, cross sections still show a dry slot aloft (above 600
mb), that could certainly curtail widespread shower development
despite the synoptic lift and weak upslope. Normally, the lift
would be sufficient to aid moistening so will have to watch this.
If it is still too dry on Wednesday, we think Wednesday night will
offer up the best opportunity for more significant and widespread
precipitation as the column fully moistens and QG lift remains in
place. The duration of this is still in question, however, as some
models track the upper level low just north of Denver, while
others would support a longer duration event with the upper level
low passing just to our south. Ensembles are generally mixed,
with >70% chance of 0.50" or more along the I-25 Corridor and
northern plains, and >50% chance of 1" for the Front Range
Mountains and Foothills. The EPS was generally trending on the
higher side while the GEFS was slightly lower (essentially
opposite the operational models). Precipitation amounts and
chances would decrease to the south and east. Temperatures will be
quite chilly Wednesday, with highs struggling (and doubtful!) to
reach the 50 degree mark in Denver and the plains.

Regarding mountain snow: The track of the upper low is favorable
for QPF (as discussed in the probabilities above). Temperatures
will also be turning colder as the core of the upper low
approaches and passes overhead Wednesday night into Thursday
morning. At this point, model averages seem reasonable bringing
minimum snow levels down to 8000 feet, but a few of the colder
solutions bring snow down even further and closer to 6500-7000
feet (20% chance). For the majority of the event, they will be
higher than that so heaviest total accumulations would likely
remain above 9500 feet, but can`t rule out a couple inches down
closer to 8000 feet. Several inches of snow are likely and the
latest QPF/snow ratio forecasts would suggest a fairly high (70%)
probability of 6-10" in the higher mountains and over the higher
passes. Thus, a Winter Weather Advisory may be needed as we get
closer to the main mountain snow event late Wednesday - Thursday
morning.

While there is uncertainty in how the upper level low finally
ejects (seems to be a combination of ejecting it into the Central
Plains with another piece shearing into the Desert Southwest), we
have increasing confidence that precipitation will be ending from
north to south on Thursday. That will set the stage for clearing
skies and likely the season`s first light freeze/frost over most
of the plains Thursday night and early Friday morning.

Beyond that, upper level ridging and dry weather is largely
anticipated for the weekend ahead. That pattern would support
temperatures returning to above normal levels with highs pushing
back into the 70s for the I-25 Corridor and adjacent plains.

&&

.AVIATION /00Z TAFS through 00Z Wednesday/...
Issued at 642 PM MDT Mon Oct 12 2026

Winds are expected to stay predominantly south/southwesterly with
gusts up to 20-25kts for the next several hours, through around 05Z,
after which they should start to turn more northerly. Guidance is
still in good agreement about low stratus moving into the area
tonight, with ceilings starting to drop after 05Z. Ceilings are
expected to lower to ~1,000-2,000 ft AGL at all three TAF sites and
be at their lowest between 12-15Z. As of the latest model guidance,
KDEN could see ceilings as low as 500 ft AGL (40-60% chance), with
mist and slightly reduced visibilities also possible (40% chance) at
the surface. Should any visibility reductions occur, we don`t
anticipate them to be any less than 4-5 SM, and we do not currently
expect any visibility reductions KAPA or KBJC.

Ceilings should start to lift in the morning, around 17-18Z, with
winds becoming more northeasterly. Winds should remain light and
north/ northeasterly throughout most of the day, becoming more
easterly with ~20-kt gusts behind the passage of a cold front in the
afternoon. Thanks to this frontal passage, we could see some light
precipitation over the area Wednesday evening, with the highest
chances at KBJC starting at around 22Z.

&&

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

&&

$$

DISCUSSION...20
AVIATION...AGS

NWS BOU Office Area Forecast Discussion