National Weather Service Forecast Discussion

Thornton Weather Forecast   
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570
FXUS65 KBOU 082337
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
537 PM MDT Sun Mar 8 2026

.KEY MESSAGES...

- Warmer temperatures continue through Tuesday.

- Next chance for light precipitation Tuesday night into early
  Wednesday.

- Strong winds and fire weather concerns possible for the second
  half of the week.

&&

.DISCUSSION /Through Sunday/...
Issued at 126 PM MDT Sun Mar 8 2026

The current synoptic pattern will not be conducive to any
significant mountain snowfall or really much of any precipitation
across the forecast area through the forecast period. However, it
will be conducive to periods of stronger winds, warmer temperatures,
and increased fire weather conditions.

For today, along with an extra hour of sunlight this afternoon,
warmer temperatures and dry conditions are forecast across the
forecast area, as flow aloft transitions to a more zonal regime.
Today marks the start of another significant warming trend, keeping
afternoon high temps well above-normal through Tuesday for much of
the forecast area. This morning`s satellite imagery shows the recent
snowfall is still in place, though significant melting has
occurred in the past 24 hours. With temperatures forecast to
climb into the mid to upper 60s across the lower elevations, and
our increasing March sun angle, expect rapid melting to what is
left over today and tomorrow.

Overnight tonight, ridgetop westerlies will increase as a 50-60kt,
700 mb jet straddles the WY/CO border. Cross sections show modest
ridgetop stability which will induce some mountain wave
enhancement, bringing gusty winds down the lee side of the Front
Range. Expecting 45-55 mph winds at our typical windy spots, a
little more at the highest elevations late tonight into early
Monday morning. The adjacent lower elevations will likely see some
puffs of gusty winds, but the strongest winds will stay above the
8,000 to 8,500 feet elevations.

Monday will be warm and dry with increasing winds. With afternoon
high temps forecast to warm into the low to mid 70s across the
plains, we will start to see some patchy elevated to critical fire
weather conditions develop where the aforementioned snow melt has
already taken place, or where no snowfall was seen with this last
storm system. While there will be marginal fire weather conditions
over much of the northern plains (RH hovers at thresholds, winds
approach thresholds, mainly along the WY border and into the
northern I-25 corridor), southern Lincoln County, where no snowfall
was reported, but over an inch of rain fell a few days ago, will see
RH values drop below critical thresholds (low teens) with a few
hours of gusts reaching 25-30 mph in the afternoon. With the main
area of concern also being the location to see the recent rain, have
opted to not issue any highlights this go around. We do suspect that
after tomorrow, fuels will have had enough time and drying to be
well on their way back to critical status for the fire weather
concerns expected later in the week (discussed below).

Moisture will start to increase on Tuesday as a cutoff low migrates
eastward across the southwest and ultimately gets reabsorbed into
the main flow as it crosses the southern Rockies. At the same time,
a shortwave will traverse the northern tier of the US, just grazing
Colorado. Lee cyclogenesis will strengthen through the day and a
cold front will slide south across Colorado in the early evening. An
initial cold front is expected early Tuesday morning that will
help moderate temps over the northern portion of the plains (keeps
highs in the upper 50s), where mid to upper 60s to low 70s will
be possible over the rest of the plains. However, it`s the second
cold front combined with the passing shortwave that will bring a
low chance at some light precipitation to our northern and central
mountains, and very light precipitation to the plains (maybe a
few hundredths). With a 700 mb jet streak over northeastern
Colorado Tuesday night and northerly flow expected behind the
front, have kept a mention of precipitation across the plains,
with the most likely area to see some being closer to the Wyoming
border where the right entrance of the jet will support the
greatest lift.

Temperatures will moderate on Wednesday behind the cold front and
northwesterly flow aloft will become established as high pressure
rebuilds over the western US once again. Expect some patchy elevated
to critical fire weather conditions to develop over the northern
plains as winds increase in the afternoon.

The northern tier looks to stay active through the week, with
another shortwave expected to cross the northern Rockies on
Thursday. This will slightly flatten out the ridge, turning flow
aloft more towards westerly over our region. Looking at output
from the Sangster Model, the GFS is showing some impressive dp/dn
values approaching 280, and pressure differences between GJT-DEN
ranging from 9-11 MSL. While the ECMWF output isn`t quite as
impressive, both models indicate potential for high winds. With
temperatures expected to rebound into the upper 60s to 70s, and
dry conditions dropping RH into the teens across all of our lower
elevations, this will be a day to stay tuned into for widespread
critical fire weather conditions and high wind headlines as we get
closer. With no significant precipitation on the horizon, and
strong winds likely hanging on into Friday (slight improvement
Saturday), critical fire weather conditions will be the main focus
through the weekend.

&&

.AVIATION /00Z TAFS through 00Z Tuesday/...
Issued at 530 PM MDT Sun Mar 8 2026

A boundary was located just to the west of DIA and should move
across with a brief shift to a westerly direction. Winds should
then trend more SSW in the 01z to 02z timeframe and then more
south by 03z.

APA will stay mainly from the south tonight while BJC will have
west winds thru 04z before shifting to more SSW by 05z.

On Mon, winds will become SW by 16z and then turn more westerly
by 19z-20Z. Gusts up to 25 mph will be possible at BJC and DIA
after 20z. Finally, VFR conditions will continue thru the period.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...9
AVIATION...RPK

NWS BOU Office Area Forecast Discussion