National Weather Service Forecast Discussion

Thornton Weather Forecast   
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949
FXUS65 KBOU 101140
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
540 AM MDT Tue Mar 10 2026

.KEY MESSAGES...

- Much above normal temperatures again today. Elevated to critical
  fire weather conditions, with Red Flag conditions along the I-25
  Corridor from northern portions of Denver Metro to the Wyoming
  border.

- Chance of snow showers for the mountains and northern plains
  Tuesday night. In addition gusty north winds up to 50 mph over
  the plains Tuesday night behind a cold front.

- Cooler on Wednesday with elevated to critical fire danger at
  lower elevations near the Wyoming border.

- Strong winds and critical fire weather concerns likely (>60%
  chance) Thursday through Saturday.

&&

.UPDATE...
Issued at 339 AM MDT Tue Mar 10 2026

Update mainly for the Red Flag Warning issued for the I-25 Urban
Corridor. See Fire Weather section for more details. Cold front is
oozing southwest across the plains, and should move through most
of Weld County and approach DIA before washing back out. That
means another day of breezy west winds developing along the I-25
Corridor, although the increasing/passing high clouds does leave
some uncertainty as to how well we`ll mix this afternoon. Stronger
cold frontal push with a period of strong, gusty winds and
potential for local blowing dust is still on track for this
evening.

&&

.DISCUSSION /Through Monday/...
Issued at 1138 PM MDT Mon Mar 9 2026

For Tue, a shallow surge of cooler air will move across the nern
plains in the morning and may reach the nrn portions of the I-25
Corridor before mixing out some by aftn.  To the west of this
boundary highs will reach the lower to mid 70`s while over the far
nern plains may stay in the upper 50`s to lower 60`s.

By Tue night, an upper level trough will move across Wyoming with
nrn CO being on the srn edge of this feature. In addition, a
stronger cold front will move across the plains in the evening
with gusty north winds behind it. Cross-sections show some
moisture will affect the nrn mtns and portions of the nern plains
closer to the WY- NE border. Furthermore, the nose of stronger
upper level jet will allow for the far nern plains to be in the
left front quadrant of the jet. Thus will see a good chc of snow
showers in the nrn mtns overnight with a chc of rain/snow showers
near the WY-NE border. Meanwhile, with 40-50 kt flow in the
boundary layer across the nern plains, there will be a brief
threat for gusty winds from 50 to 60 mph associated with the
showers. At this time, not sure about overall coverage and how
long they will last so have decided not to issue any high wind
highlights.

On Wed, drier air in NW flow aloft will move across the area. Latest
data suggest some moisture may linger thru the mid morning hours in
the mtns which may lead to a slight chc of snow showers.  Otherwise
it will be dry with cooler temperatures as highs drop back into the
50`s across the plains.

For Wed night thru Thu night the flow aloft will become more WNW
with only some higher level moisture embedded in the flow.  Will see
very windy conditions develop over the higher terrain late Wed night
which will continue thru Thu night.  At this time, hard to say how
strong of a mtn wave there will be on Thu and whether the stronger
winds will mix down to lower elevations below 6000 ft. For now, it
appears areas in and near the nrn Foothills and adjacent plains,
closer to the WY-NE border, will have some potential for stronger
winds. Highs on Thu will rebound back into the upper 60`s to
lower 70`s across the plains as downslope warming occurs.

On Fri, dry WNW flow aloft will remain over the area.  A weak front
may move into far nern CO in the morning.  However, by aftn a sfc
lee trough will intensify from ern WY into ern CO.  Thus it will be
another windy day over the high terrain and portions of the plains.
With downslope low level flow in place, high across the plains will
be in the 70`s.

For the weekend, an upper level trough will move from the Pacific NW
into the area Sat night into Sun.  Ahead of this feature, there
could be another round of stronger winds over the higher terrain and
portions of the plains on Sat with another day of much above normal
temps.  Sat night there will be a strong cold front moving across
the area with much cooler temperatures for Sun.  Meanwhile,
depending on how much moisture there will be behind the front,
there could be a chc of snow across the plains Sat night into Sun
as the upper level trough moves across. In the mtns, there should
be a good chc of snow as well.

&&

.AVIATION /12Z TAFS through 12Z Wednesday/...
Issued at 540 AM MDT Tue Mar 10 2026

VFR will persist through the TAF period. The shallow backdoor
front continues to ooze through northeast Colorado and should be
approaching KDEN by 1330Z. It could end up straddling the airport
or working through for a brief time through 1530Z, so opting for a
compromise of winds with ESE during that period for now...but
could be anywhere from northeast with a better push, or southerly
if the front still washes out. It will be close. After that,
expect a more southwesterly flow to develop but the weak front (as
well as BKN high clouds) will likely delay the onset of gusty
west winds, which could now end up closer to 20Z at KDEN. Once
they do increase from daytime heating and mixing, enough flow
aloft to support peak gusts up to 30 kts although averages should
be just a little less than that from the west. That`s getting
close at times to crosswind thresholds for N-S runway ops.

Meanwhile, at the other two TAF sites...KAPA will be far enough
south to keep the front out early this morning, while KBJC will be
right on the edge so winds may become VRB 14Z-18Z. Both of those
sites will see earlier arrival of gusty west winds than KDEN due
to weaker inversions, with KAPA likely to go first by 16Z-18Z.

A gusty cold front is still on track to move through all
terminals around 02Z-04Z Wednesday. Northeast winds up to G35
knots or more are possible behind the front. Wind will
subsequently weaken by 05Z-06Z and turn more easterly as an
anticyclonic flow pattern develops across northeast Colorado.
We`ll keep a SCT deck near 5K ft in the forecast due to upslope
and some moisture behind the front, but overall it looks like a
small 20% threat that ceilings would be low enough for IMC.

&&

.FIRE WEATHER...
Issued at 354 AM MDT Tue Mar 10 2026

We`ve issued a Red Flag Warning today from noon - 7 pm for the
I-25 Urban Corridor. A weak cold front is oozing back into
portions of this area (mainly Weld and eastern Larimer Counties)
but that should be eroding as shallow easterlies wash out due to
pressure falls over the High Plains. However, it will delay the
development of gusty winds to early to mid afternoon for areas
north of Denver. That said, once they do mix we should see gusts
to 30 mph per mixed layer data, and humidities drop to around 13%.
The rest of the plains roughly east of Fort Morgan will see
cooler temperatures and lighter winds persist much of the day.

A cold front brings a gusty wind shift this evening (6 pm northern
border and to Denver by 9 pm). While temperatures will be cooler
Wednesday, locally elevated to critical fire weather conditions
will be possible in the afternoon over far north and northeast
Colorado where winds will still gust to 35 mph and drier air
arrives from the north.

Very warm and dry conditions return to the area Thursday through
Saturday. A surface low passing north Colorado will tighten the
pressure gradient, bringing very windy conditions to portions of
the area on Thursday. Strong winds are also a possibility for the
foothills if a mountain wave forms. Windy conditions will
continue to be possible Friday and Saturday under an increasing
northwest flow aloft. Overall, there will be elevated to critical
fire conditions Thursday through Saturday below 7000 feet.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from noon today to 7 PM MDT this evening for
COZ238>240-243.

&&

$$

UPDATE...20
DISCUSSION...RPK
AVIATION...20
FIRE WEATHER...RPK

NWS BOU Office Area Forecast Discussion