National Weather Service Forecast Discussion

Thornton Weather Forecast   
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936
FXUS65 KBOU 100548
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1148 PM MDT Mon Mar 9 2026

.KEY MESSAGES...

- Much above normal temperatures again Tuesday, with elevated to
  critical fire weather conditions. Highest along the I-25
  Corridor from northern portions of the Denver Metro area 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 possible
  Thursday through Saturday.

&&

.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 Wyomning 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 /06Z TAFS through 06Z Wednesday/
... Issued at 1140 PM MDT Mon Mar 9 2026

VFR will persist through the TAF period. Winds have mostly turned
southwesterly and should persist through about 15Z-16Z before
starting to increase again. However, there is a shallow backdoor
cold front to watch that`s moving into northeast Colorado. That
could turn winds northeasterly or even variable (30-40% chance) for
a brief bit 12Z-16Z. For now, we`ve kept the prevailing southwest
direction in the TAF but still something to watch. We do think
daytime heating/mixing will dominate after 16Z which means an
increase in westerly winds through 18Z-21Z, continuing through at
least 24Z. Peak gusts up to 35 knots are possible at BJC and up to
30 knots at DEN and APA, although averages should be about 5 kts
less than that and mostly below critical N-S crosswind thresholds at
KDEN.

A cold front is still on track to move through all terminals around
02Z-04Z Wednesday. Gusty winds up to 35 knots are possible behind
the front from the northeast. Wind should weaken toward 06Z and turn
more easterly as an anticyclonic flow pattern develops across
northeast Colorado. We`ve introduced a SCT deck at 5K ft 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 1138 PM MDT Mon Mar 9 2026

It will be another warm dry day Tuesday over northeast Colorado
with relative humidities in the teens. Elevated to locally
critical fire weather conditions are expected during the afternoon
hours, espeically from along the I-25 Corridor from Denver north
to the Wyoming border where wind gusts to 35 mph will be possible.
A cold front brings a wind shift Tuesday evening and cooler
temperatures for Wednesday. Locally elevated to critical fire
weather conditions will be possible in the afternoon over far
north and northeast Colorado where breezy conditions are expected.

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...
None.

&&

$$

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

NWS BOU Office Area Forecast Discussion