National Weather Service Forecast Discussion

Thornton Weather Forecast   
Today's Forecast Story   
149
FXUS65 KBOU 220100
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
700 PM MDT Sat Mar 21 2026

.KEY MESSAGES...

- Record heat and critical fire weather conditions continue this
  afternoon and evening. Several sites may see 90F high
  temperatures.

- Brief drop to near normal temperatures Sunday.

- Return of unseasonable warmth, potential record heat, and more
  fire weather concerns again by Tuesday and Wednesday. Record
  heat increasingly likely (>80% chance) across the Denver metro.

&&

.DISCUSSION /Through Saturday/...
Issued at 1235 PM MDT Sat Mar 21 2026

Today`s forecast largely remains on track, as we continue to
simply watch the temperatures across most of the forecast area.
There are already some rather impressive temperatures noted across
the I-25 corridor and foothills as of the time of this AFD (1230
PM). Nearly every ASOS/AWOS/RAWS station below 6,500ft has already
made it into the low 80s, with a few >85F temperatures noted at
BDU/GXY/EIK/LMO. We`ve been a touch slower to fully mix out some
of the lingering near surface moisture, but observations from the
high country suggest that this won`t be the case by mid-afternoon.
Winds may also be a little slower to work their way east, but
there should still be a push of wind across the I-25 corridor
between 3-7 PM.

Meanwhile, we`re starting to see more wind across the high
country, where a Red Flag Warning is already in effect. Like the
plains, most locations haven`t completely mixed out yet, but a
continued increase in winds (and subsequent decrease in dew
point/RH) is still in the forecast through the evening hours.

A cold front should push southward across the lower elevations
after midnight tonight, bringing cooler temperatures and an
increase in moisture. Sunday will at least feel a little closer to
normal, with highs in the 60s and weaker easterly winds across
most of the plains. There`s maybe just enough moisture for a few
light rain/snow showers across the Front Range but chances for
measurable precipitation are still low (generally 10F temperature departures are near 50-90%, with
higher confidence of above normal temperatures across the
mountains.

&&

.AVIATION /00Z TAFS through 00Z Monday/...
Issued at 646 PM MDT Sat Mar 21 2026

A boundary is working its way towards DIA this evening and will
likely produce WNW winds with gusts up to 22 knots from 01-03Z.
Winds will be out of the west at all terminals this evening with
speeds generally around 10 knots. A cold front will move across
the terminals between 06-09Z. This will shift winds to the north
with gusts up to 25 knots right behind the front. By the morning,
there will be low level moisture in place behind the front. With
light upslope flow, it is possible that a cloud deck around 2,000
feet develops at all terminals. However, it seems dry enough that
a scattered layer was put in the forecast.

East winds will develop tomorrow for the majority of the day with
gusts up to 20 knots. There is a slight chance that nearby virga
showers produce ceilings around 6,000 feet late tomorrow afternoon
and evening.

&&

.FIRE WEATHER...
Issued at 1235 PM MDT Sat Mar 21 2026

Critical fire weather conditions are continuing to develop across
the higher elevations and into the far western I-25 corridor this
afternoon, and should persist through most of the afternoon and
evening hours. Only minor tweaks to the forecast were made in this
period and no changes to the Red Flag Warning were made today.

Cooler temperatures and weaker winds should limit the overall fire
danger on Sunday and Monday. As a ridge begins to redevelop to the
southwest and zonal flow increases, another warming/drying trend
is expected by Tuesday/Wednesday. Elevated to critical fire
weather conditions look likely both days, and may extend into
Thursday depending on the timing of our next cool front.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 10 PM MDT this evening for COZ211-213>216-
238>245-248-250.

&&

$$

DISCUSSION...Hiris
AVIATION...Danielson
FIRE WEATHER...Hiris

NWS BOU Office Area Forecast Discussion