Arvada, Colorado 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

896
FXUS65 KBOU 221112
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
412 AM MST Mon Dec 22 2025

.KEY MESSAGES...

- Critical fire weather conditions today in and near the foothills
  and across the Palmer Divide and South Park.

- Record warmth likely across most of the I-25 corridor and plains
  today, with highs in the upper 60s to mid 70s.

- Warm and dry through Wednesday, and Christmas still warm for the
  plains. Hints of a more wintry pattern in the mountains Thursday
  into Friday.

&&

.UPDATE...
Issued at 153 AM MST Mon Dec 22 2025

Dry zonal flow aloft will remain over the area today thru tonight.
Cross-sections continue to show cross-barrier flow in the 50-55kt
range this morning thru mid aftn.  However, there really isn`t much
of a mtn wave shown in the hi res data.  Most gusts will be in the
50 to 60 mph over the higher terrain with a few areas seeing 60-70
mph.  Meanwhile, with favorable downslope flow in place record highs
are likely across portions of the I-25 Corridor and plains this
aftn.

UPDATE Issued at 831 PM MST Sun Dec 21 2025

Latest 00Z data suggests gusty west winds will have a higher
chance (60-70%) of spreading from the foothills onto the nearby
adjacent plains and Palmer Divide. While not as strong as the
foothill gusts to ~60 mph in wind prone areas, a few gusts of
30-40 mph will be possible in Boulder, CO-93, and the Palmer
Divide as we see better mixing. We`re still unsure if those winds
come out as just channels or even secondary mountain waves, but
enough threat with the low humidity and extremely dry fuels to
expand the existing Fire Weather Watch to Boulder and the western
Denver suburbs, as well as the Palmer Divide where airmass will
be more strongly mixed.

&&

.DISCUSSION /Through Sunday/...
Issued at 327 PM MST Sun Dec 21 2025

Fairly impressive temperature gradient across the I-25 corridor
this afternoon, with the southeast side of the Denver metro
sitting in the upper 60s (and a 70F at CFO), while 50s are a much
more common number off to the north. If the current temperature at
DEN holds at 67F we`d tie another daily record high.

Main story for the start of the week will be the near-record to
record high temperatures across most of our lower elevations.
Ridging is starting to slowly build across the southern CONUS, but
there`s still just enough flow aloft (generally 50-70kt at/above
ridgetop) for some gusty winds to develop. Guidance tries to
briefly bend that back down into the lower foothills. The
combination of guidance that worked well with the last couple wave
events (HRRR/RRFS/RGEM) all bring gusty winds down to the base of
the foothills. Combined with the record warmth and drying airmass,
we could see some elevated to critical fire weather conditions.
More on that in the Fire Wx section. There`s much less confidence
that any gusts will make it into the lower elevations, but warming
mid-level temperatures and the increased downslope component
should allow temps to reach the mid 70s in some places. Tomorrow`s
record high at DEN (70F) is likely to be broken, and other places
in the eastern plains may shatter their daily records by several
degrees.

For Monday night through Wednesday, upper level ridging will be
well established over the south central and southeast part of the
country with a mild and dry southwest flow aloft over Colorado.
For Thursday, southwest flow aloft increases as the upper level
ridge is nudged eastward by a large upper level trough off the
west coast of North America. For Tuesday, Wednesday (Christmas
Eve), and Thursday (Christmas Day), temperatures will continue to
be well above average with highs in the mid 60s to lower 70s
across northeast Colorado. Periods of high clouds are expected, so
if we end up seeing a day where high clouds persist for most/all
day, we could fall short of the mid 60s. Winds don`t look to be an
issue especially Tuesday and Wednesday under weak flow aloft. As
flow aloft increases on Thursday, gustier winds will be possible
for the mountains and foothills, but less than we saw this past
week. The increasing southwest flow aloft will transport Pacific
moisture into the area Thursday (Christmas Day) bringing snow to
the mountains. Southwest flow aloft tends to bring better/heavier
snow to the western mountains versus the central mountains.

For Friday and next weekend, an upper level trough dives
southeast along the west coast closing off over central to
southern California. This helps create a split low aloft across
western North America. Over Colorado on Friday, we`ll see
southwest flow aloft continue with a chance for snow (possibly a
little valley rain) in the mountains. High temperatures begin to
cool slightly but stay well above normal with highs in the upper
50s to mid 60s. For the weekend, there`s some uncertainty where
the cutoff low over the southwest part of the country will be.
Likely too far southwest of Colorado to bring much precipitation
east of the mountains. However, the mountains mainly see snow,
heaviest in the southwest mountains. A trough in the northern
branch passes well north of Colorado, but a weak cold front slides
southward bringing cooler, near normal temperatures for the
weekend. Even though there`s a good amount of uncertainty on the
placement of the closed low, models have been in good agreement
with this cool down for the weekend.

&&

.AVIATION /12Z TAFS through 12Z Tuesday/...
Issued at 408 AM MST Mon Dec 22 2025

VFR conditions will continue thru the period. Winds remain
drainage early this morning and should continue that direction
thru midday. For the aftn, will shift winds to the west in the
19z-20z time period. There could be sporadic gusts up to 25 mph
until 23z. Winds should decrease after 23z and then shift back to
drainage in the 03z-04z time period.

&&

.FIRE WEATHER...
Issued at 153 AM MST Mon Dec 22 2025

Critical fire conditions will be in place from mid morning through
late afternoon in and near the foothills, the Palmer Divide and
South Park.  The strongest winds will focus in the foothills of
Larimer and Boulder counties, where wind gusts up to 60 mph will
occur from late this morning thru mid afternoon with localized gusts
up to 70 mph possible. Elsewhere in the foothills expect wind gusts
from 45 to 55 mph.

Meanwhile across the Palmer Divide, South Park and near the
foothills wind gusts from 35 to 40 mph will occur. Humidity levels
will drop down to 8% to 15% this afternoon.

By late afternoon into the early evening hours winds should
gradually dimininsh in all areas with a decrease in fire weather
conditions.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from 8 AM this morning to 5 PM MST this
afternoon for COZ214>216-238-239-241.

&&

$$

UPDATE...RPK
DISCUSSION...Hiris/12
AVIATION...RPK
FIRE WEATHER...RPK