775
FXUS65 KBOU 130042
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
542 PM MST Fri Dec 12 2025

.KEY MESSAGES...

- Gusty west winds in/near the foothills leading to elevated fire
  weather conditions, mainly tonight.

- Cold front to bring falling temperatures Saturday afternoon
  over the northeast plains.

- More warmth through next week.

- Increasing potential for another downslope wind event Wednesday into
  Thursday next week over the high terrain and foothills.

- Fire Weather concerns remain in place across a large portion of the
  region given the continued warmth and drier/windier conditions.

&&

.SHORT TERM /Through Saturday/...
Issued at 101 PM MST Fri Dec 12 2025

Northwest flow aloft will continue through this weekend with an
upper level high off to the west where mild and dry conditions
will prevail. A polar low will be centered over the Great Lakes
bringing arctic air to the north central and northeast part of the
country. This arctic isn`t far away from Colorado with
temperatures in the teens and lower 20s over northwest Nebraska
and northeast Wyoming.

For tonight, surface pressure lowers along the base of the
foothills. Expect downslope winds to increase in the Front Range
Mountains and foothills. Typical windy locations are expected to
see gusts to around 60 mph. Some gusty winds will spread onto the
urban corridor where gusts to 40 mph will be possible overnight
and into Saturday. This will result in a warm night where the
winds persist.

The temperature forecast for Saturday will be a tricky one as the
arctic air sneaks into northeast Colorado. Models greatly vary on
the amount of arctic air that makes it into northeast Colorado.
The 2PM temperature at DEN on the HRRR is 64F, while the GFS shows
44F. Typically the colder air advances more quickly and farther
westward than the models show. The morning will start off mild
with temperatures expected to reach the 50s to lower 60s along the
urban corridor and nearby plains. As the arctic air moves into
the area temperatures are expected to fall during the afternoon
and by sunset temperatures could be in the 30s or even 20s. The
arctic air is expected to be shallow, only up to 7,000-8,000 feet
MSL, so don`t expect the cold to advance very far into the
foothills.

&&

.LONG TERM /Saturday night through Friday/...
Issued at 101 PM MST Fri Dec 12 2025

It`s starting to feel as though the warmer temperatures are becoming
a Mid-West goodbye...

We`re seeing above average temperatures through all of next week
with little in the way of moisture for the plains. Ensembles are
showing higher probabilities, 70+ percent, of 10 to 15 degrees above
average daytime highs and overnight lows all of next week.

Moisture, if we`re able to get any, will be mostly confined over the
high country and should be snow with a possibility, 30-40%, of a
rain/snow mix in the mountain valleys. Currently targeting Wednesday
for any moisture across the mountains as the upper level flow
becomes more zonal and tries to wring something out. The pattern
just isn`t good but it`s a very typical La Nina pattern for us in
Colorado.

Speaking of Wednesday, windy. Yes it`s further out there in time
and yes confidence is increasing and yes there are uncertainties
but digging into the ensembles and the larger picture we can gain
some knowledge. Cluster analysis shows some pretty decent camps of
stronger zonal flow with anomalous heights over the inter-
mountain west. EFI and SOT from the ECE are high and low
respectively in terms of wind/wind gusts meaning, the individual
members are showing higher confidence in an impactful event. Even
looking at NBM in DESI we have a 40-50% chance of maximum gusts at
the base of the foothills exceeding 70 MPH. Now the
uncertainties, does the wind stay more 290-310 degrees aloft or
does it trend slightly back towards 330-350 degrees? Does the
moisture content on Wednesday become too deep to disrupt any kind
of thermal inversion preventing the winds aloft to be forced
downward? Don`t have all the answers yet and we may not until
Tuesday...Chinook are tough!

We don`t really lose the stronger forcing aloft with the more
expected zonal-ish flow so we keep the stronger winds around through
the end of the work week.

Can`t forget to mention fire weather, not that anyone wants to hear
it. We`re dry and mild/warm, and we have enough wind to continue to
dry out any early December moisture, if it`s not already gone from
the lower foothills, and the plains never really got it anyway. As
we get into the later part of next week we see increasing potential
for at least elevated fire weather conditions with the wind,
receptive fuels, and lower RH values.

&&

.AVIATION /00Z TAFS through 00Z Sunday/...
Issued at 442 PM MST Fri Dec 12 2025

VFR through the TAF period. Current westerly winds at KDEN are
expected to trend towards drainage through the evening (by 3/4Z).
KAPA winds are expected to be light and variable before also
turning to drainage. Gusty west winds are expected at KBJC through
the overnight hours as a mountain wave is expected to reamplify.
There is a chance (15-20%) a few fingers of gusty winds spill
into the plains and make their way into KDEN, with the greatest
chances between 12-14Z that would lead to drainage winds shifting
to the west and gusting between 25-30 kts.

Winds are expected to shift to the N and then NE by late morning as
a cold front slides south across the plains. Should see some gusty
winds (20-25 kts) for a few hours as it moves through. There has
been a slight delay in timing with the latest guidance, though
models are notoriously late on cold front arrivals, so we expect
the gusty NE winds somewhere between 17-19Z. Winds should trend to
the east for the late afternoon and winds should begin to decrease
by around 22Z.

&&

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

&&

$$

SHORT TERM...12
LONG TERM...Heavener
AVIATION...9

NWS BOU Office Area Forecast Discussion