410
FXUS65 KBOU 221135
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
435 AM MST Thu Jan 22 2026

.KEY MESSAGES...

- Arctic air moves into the area tonight and holds through at
  least Sunday morning, with below zero wind chills for the
  plains.

- Areas of mainly light snow for the plains Friday - Friday
  night, lingering into Saturday morning. Mountains will see
  several inches for a change.

- Lots of uncertainty regarding any potential moderation Sunday.
  Stronger signal of temperatures returning to near normal for
  Monday through much of next week.

&&

.UPDATE...
Issued at 336 AM MST Thu Jan 22 2026

Forecast is on track for the arctic air intrusion. Yesterday`s
crew did a great job with knocking down forecast temperatures to
anticipated levels, and we just reiterated that forecast again
tonight.

The leading edge of arctic air is marching south from Canada and
is currently pushing into northeast Montana and northern South
Dakota in these wee morning hours. While we won`t see a true
"arctic blast" with strong and gusty winds, it will be more like
an "arctic ooze" as the strongest cold advection occurs across the
Central Plains and Midwest tonight. With a more easterly flow
pattern, the arctic air only slowly backs in from the east
overnight.

One interesting note to consider is for the forecast temperatures
tomorrow. It`s a bit tricky as latest indications are that we`ll
attempt to erode some of this shallow arctic air off the Palmer
Divide. This is a tough task indeed, but even some of our trustier
low level cold air models like the NAM and NAMNest even show some
moderation into the upper 20s/lower 30s in parts of Denver.
However, experience would suggest this would only be a relatively
narrow sliver in the southern suburbs of north slope of the Palmer
since a Denver cyclone would wrap up. That feature would essentially
anchor the arctic air in place (or even reinforce it into the
norther suburbs of Denver) so we`ve continued with the colder
than guidance forecast. The same can be said for the rest of
this forecast, leaning heavily toward the colder ECMWF ensemble
guidance.

A stiff easterly wind over the plains tonight through Friday
evening all but ensures wind chill readings will drop to less
than -15F, so we`ve issued a Cold Weather Advisory for those
areas. This Advisory does not include the I-25 Urban Corridor,
since our winds will be weaker and temperatures will be just a
few degrees "warmer". This doesn`t mean it won`t be COLD! So
bundle up accordingly. Also, for the Advisory, rather than
worrying about some slight moderation in wind chill readings
during the day Saturday as winds subside, we`ll use the keep it
simple approach and have a long duration Advisory that goes from
late tonight all the way through early Sunday morning. Low
temperatures Saturday night should drop below zero over almost
all of the plains. And with fresh but light snow cover air
temperatures of -10 to -20F would be possible in the cold spots
on the plains Saturday night if we clear out.

With regard to snow, We`re still on track for eventual moistening
of the boundary layer in the arctic airmass late tonight and
Friday. That will likely bring in some light snow or flurries onto
the plains. Moisture deepens Friday afternoon through Friday
night under persistent weak QG synoptic forcing, some
frontogenesis, and then arrival of mid level plume originating off
the upper level trough over the southwest United States. That is
still expected to bring an uptick in snowfall to the mountains
starting tomorrow afternoon, and then onto the plains in the
deepening moisture/weak upslope profile Friday night into Saturday
morning. There was just a slight increase in total QPF, but still
looks like just a light snow event of 1-3 inches of fluffy dry
snow over the plains, 2-4 inches for the foothills and Palmer
Divide, and 3-8 inches most of the mountains. Somewhat heavier
totals of 4-10 inches can be expected in the mountains of Summit
County and the I-70 Corridor, so we`ve issued a Winter Weather
Advisory there from 11 am Friday through Saturday. Look for
impacts to ski travel and potential lengthy commute times for
those looking for some rare fresh powder.

Finally, the potential warmup for Sunday is looking less and less
likely. Even the GFS/GEFS is showing another wave dropping south
into the back of the impressive snow/ice storm that will hit a
large chunk of the Southern Plains, TN/OH River Valleys, and
points east/northeast through Central Atlantic states and portions
of New England. We`re not as cold as some guidance suggests
(teens), but trending to highs only in the lower 20s for now.
There`s a 40-50% chance (and growing) that we don`t even hit 20F.
The warmup for Monday into much of next week is still on track.

&&

.SHORT TERM /Through Thursday/...
Issued at 225 PM MST Wed Jan 21 2026

Relatively quiescent conditions continue this afternoon under a
broad area of dry, northwesterly flow aloft. Temperatures have
generally made it into the mid to upper 40s across the plains
(with DEN at 48F so far) with slightly cooler temperatures closer
to our northern CWA border.

Surface obs indicate another cold front is creeping into our
forecast area this afternoon, and this should bring some cooler
temperatures into the region for tonight and tomorrow. Highs on
Thursday should remain in the 30s as cold air continues to slowly
push into the region during the day. There should be a gradual
increase in cloud cover through the day, but otherwise the weather
should remain quiet.

&&

.LONG TERM /Thursday night through Wednesday/...
Issued at 225 PM MST Wed Jan 21 2026

Longwave trough over eastern North America is still on track to
bring arctic air to the central and eastern parts of the country,
including eastern Colorado. A strong surface high sinks south into
the Northern Plains Friday. We won`t see a sharp cold front, but
persistent northeast to east low level flow will advect the arctic
air into the region. Most of the model show highs of 15 to 25F
Friday and 5 to 15F for Saturday across northeast Colorado, but
the GFS/GEFS are about 10F warmer. If memory serves me right, the
GFS/GEFS were warm outliers for arctic events last winter and the
colder solutions (most other models) were more accurate. Feel this
is the same case with this upcoming arctic blast, so lowered
temperatures for Friday through Sunday. Saturday is on track to be
the coldest day with highs 5 to 15F degrees over northeast
Colorado. Saturday night is expected to be the coldest night. How
cold is still unclear, it will depend on how much clearing we see
overnight. Where it clears, lows for Saturday night have the
potential to reach -10F to -20F. Cold Weather Advisories may be
needed over eastern Colorado Friday night through Sunday morning
if models continue to push wind chills below -15F.

As far as snow goes, we`ll likely see light snow/flurries Friday
over eastern Colorado associated with the easterly upslope low
level flow. For late Friday, Friday night, and into Saturday,
there are a few features out there that could bring us snow.
First, moisture is expected to increase from the southwest. For
lift, we`ll see an upper level trough drop southward across the
region and the right entrance region of the jet will be over the
region. Placement of the best lift is still somewhat uncertain,
but the latest model cycle favors central and southern Colorado
for the best lift and snowfall. For areas north and northeast of
Denver, up to 2 inches of snow looks on track with slightly more
possible over the mountains and over/south of Denver. Drier air
moves in from north Saturday/Saturday night with dry conditions
expected over the area by midnight Saturday night.

Flow aloft turns west-northwest and a lee side surface trough
forms over eastern Colorado Monday. This will bring milder Pacific
air to the region. High temperatures are expected to climb above
freezing with highs in the upper 30s to mid 40s. West-northwest
flow aloft with possibly some ridging is expected over the Central
Rockies Tuesday and Wednesday. Near normal temperatures (highs in
the mid to upper 40s) and dry conditions are expected Tuesday and
Wednesday.

&&

.AVIATION /12Z TAFS through 12Z Friday/...
Issued at 435 AM MST Thu Jan 22 2026

VFR will persist through most of this TAF period, but areas of
stratus and MVFR ceilings expected toward 12Z Friday. With regard
to the winds...light southwest winds are expected to prevail
through about 15Z-16Z. Then they`ll become light and VRB for a
couple hours before making the transition to NE-E winds at 8-12
kts 18Z and beyond. However, after about 03Z Friday there is
considerable uncertainty with wind progression as a weak cyclone
is expected to develop right near KDEN. While that would almost
certainly bring NNW winds to KBJC, other airports like KAPA and
KDEN will be on the edge of the shear zone/cyclone. As a result,
the slightly enhanced E-SE winds 00-03Z could become VRB anytime
after 03Z, and more likely toward 06Z. There is higher probability
(but only 50-60%) that we turn more northerly at KDEN late in the
night after 10Z. Boundary layer moisture remains quite limited
despite the frontal surge through tonight, but eventually we
moisten sufficiently for areas of stratus around 2,000 ft AGL to
develop after 10Z, and most likely toward 12Z-15Z Friday.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 11 AM Friday to 5 PM MST Saturday
for COZ034.

Cold Weather Advisory from 3 AM Friday to 9 AM MST Sunday for
COZ042-044>051.

&&

$$

UPDATE...20
SHORT TERM...Hiris
LONG TERM...12
AVIATION...20

NWS BOU Office Area Forecast Discussion