National Weather Service Forecast Discussion

Thornton Weather Forecast   
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024
FXUS65 KBOU 050011
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
511 PM MST Wed Nov 4 2026

.KEY MESSAGES...

- Precipitation is moving into Park County and southern Summit and
  Jefferson Counties as of late this afternoon. Precipitation
  will continue in these areas through tonight with snow falling
  mainly above 7,500 feet. Snowfall amounts of 2-8" expected with
  isolated higher amounts possible.

- The highest snowfall amounts and worst road conditions are
  expected for western Park County, possibly extending into
  northern Park County.

- Pleasant temperatures and dry conditions are expected Thursday
  through early next week.

&&

.DISCUSSION /Through Wednesday/...
Issued at 210 PM MST Wed Nov 4 2026

Water vapor imagery shows a cutoff shortwave trough just south of
Grand Junction this afternoon. This trough has plenty of
instability associated with it since there are numerous
thunderstorms across western Colorado and eastern Utah. Meanwhile,
there has been plenty of sunshine across our forecast area as the
high cloud cover previously anticipated never fully developed.
Some weak instability has developed over and near South Park with
the SPC mesoanalysis page showing 250 j/kg of surface CAPE and mid
level lapse rates peaking at 8.5 C/km. As the forcing from PVA
ahead of the trough moves closer to Park County, showers and
perhaps a couple of storms will form late this afternoon. Compared
to model run yesterday, this system will track a bit further
south. As a result, the vast majority of the precipitation will
stay south of I-70 with minimal amounts, perhaps a trace to 2" of
snow, forecast near the Eisenhower Tunnel. Conditions still look
prime for moderate to briefly heavy snow in western and southern
Park County with forecast amounts between 2-8" with higher amounts
in the Mosquito Range. The Winter Weather Advisory is in effect
for those areas but it is important to note that there are areas
in the advisory, the I-70 corridor and northward, that will see
little to no impacts from this system. Some showers may extend
onto the Palmer Divide but the area of precipitation on the plains
will be very minimal. PoPs and QPF were decreased across the
southwestern Denver metro and anything north of I-70.

There will be brief ridging that moves over Colorado on Thursday
which will lead to dry conditions and seasonal temperatures.

By Friday, a weak trough with a northerly jet behind it will bring
some weak forcing to the mountains of our forecast area. There may
be some light snow with amounts staying under 2" in the mountains
and no snow below that.

If you like temperatures in the 60s or low 70s with sunny skies
and light winds, you will enjoy Saturday through the middle of
next week if you live at lower elevations. The bad news is there
is almost no chance for mountain snowfall Saturday through
Wednesday and that will hurt the already limited snowpack in the
mountains. It`s not until the 3rd week of November when models are
indicating potential for more widespread precipitation across
Colorado.

&&

.AVIATION /00Z TAFS through 00Z Friday/...
Issued at 500 PM MST Wed Nov 4 2026

VFR conditions are expected through this TAF package. Winds are
forecast to generally remain below 10kts for the next 24 hours at
all 3 TAF sites. We are starting to see a few showers go up to the
south and west of APA, there is still pretty high uncertainty on
how these showers will evolve and impact the terminals,
especially APA and BJC. There is a low to medium chance (30% to
45%) that APA could see occasional light rain over the next 3 or
so hours. Confidence in precip making it to DEN and BJC are lower,
but there is still a low chance (10% to 20%) of light rain at
these areas. CIGs should remain around 5000ft with this activity.
Ceilings will start to lift late this evening and early overnight.
Tomorrow, winds will go light and variable in the late morning,
turning more NE for the early afternoon.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 2 AM MST Thursday for COZ034-037.

&&

$$

DISCUSSION...Danielson
AVIATION...AP

NWS BOU Office Area Forecast Discussion