208
FXUS65 KBOU 131740
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1040 AM MST Sat Dec 13 2025

.KEY MESSAGES...

- Cooler for northeast plains this weekend. Otherwise,
  unseasonably mild and dry across the region through early next
  week, with weaker winds after today.

- Strong downslope winds expected Wednesday, which may lead to
  fire weather concerns for the lower elevations and foothills.

- Increased potential for mountain snow late Wednesday into
  Thursday.

&&

.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 /18Z TAFS through 18Z Sunday/...
Issued at 1040 AM MST Sat Dec 13 2025

VFR to prevail through tonight and Sunday. Northwest winds will
shift to the northeast around 19Z as a cold front pushes through.
Winds then slowly turn clockwise, to the east and then southeast
after 00Z Sunday. Southerly winds then prevail tonight and Sunday
morning. A Denver cyclone is expected to form Sunday morning,
possibly bringing north to northwest winds towards 18Z Sunday.

&&

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

&&

$$

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

NWS BOU Office Area Forecast Discussion