National Weather Service Forecast Discussion

Thornton Weather Forecast   
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223
FXUS65 KBOU 251130
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
530 AM MDT Thu Jun 25 2026

.KEY MESSAGES...

- Notably cooler today, with scattered showers/t-storms continuing
  through this evening, albeit of lesser intensity than prior
  days. Expect continued smoke and hazy skies.

- Widespread and prolonged critical fire weather conditions will
  be present in the high country this weekend as warm, dry and
  windy conditions develop.

- All areas will trend warmer and drier this weekend, with little
  change into next week.

&&

.DISCUSSION /Through Wednesday/...
Issued at 1252 AM MDT Thu Jun 25 2026

Scattered showers with a few embedded (and weak) thunderstorms
will continue to impact our area through the remainder of the
night and even past sunrise, associated with the passage of a
couple of successive shortwaves aloft. In the wake of this
widespread precipitation, a notable stratus deck will remain
anchored over the plains through much of the morning, along with
potential for patchy fog. Continued smoke transport from wildfires
to our west will unfortunately maintain relatively poor air
quality (especially in the mountains) and hazy sky conditions.

To our south, a surface low will sustain cool and moist easterly
flow into our area, making for a notably cooler day and likely
helping to maintain some stratus into the early to mid-afternoon
hours for parts of the plains, and temperatures will struggle to
climb above the mid 70`s. As a result, we should be more reliably
capped at lower levels despite continued healthy buoyancy aloft,
thereby tapering the threat of severe thunderstorms. A few strong
to marginally severe storms wouldn`t be out of the question for
the plains if we can clear out sufficiently and/or early enough,
but for the most part, the lower elevations are favored to see
scattered showers and more isolated convection. Terrain will be a
more relevant factor in convective initiation today, and as such,
afternoon thunderstorms look to return to our mountains where
capping will be less of a limitation.

We`ll begin trending warmer and drier on Friday as flow aloft
becomes more zonal and some warm advection returns. Enough mid-
level moisture is retained to allow for isolated, weak high-based
showers and thunderstorms in the afternoon, but any convection
should remain sub-severe, mainly capable of localized breezy
outflows as drier surface conditions develop.

By this weekend, a robust closed low will develop over the PacNW
and begin migrating southward. Along its eastern periphery, strong
and dry southwest flow aloft will impinge on Colorado, with gusty
winds being most prominent in our high country. Combined with a
warm and dry airmass over and east of Colorado beneath the
strengthening ridge, this will translate into much warmer
conditions, with temperatures quickly rebounding well into the
90`s for the lower elevations. Of greater concern, fire danger
will ramp up several notches in the mountains and high valleys,
persisting through the weekend and into early next week. More on
that in the Fire Weather Discussion below.

The aforementioned low is then slated to lift rapidly northeast
into the northern plains, with additional troughing over the West
Coast sustaining moderately dry southwest flow aloft. Continued
warm, breezy and mostly dry conditions are thus favored.

&&

.AVIATION /12Z TAFS through 12Z Friday/...
Issued at 524 AM MDT Thu Jun 25 2026

Scattered showers and isolated, weak thunderstorms will continue
to impact the Denver area through this afternoon. The convective
potential this afternoon carries the greater uncertainty and will
be at least partially dependent on the extent of clearing of lower
stratus late morning/early afternoon. Forecast leans towards a
more stubborn stratus deck, particularly with lingering smoke in
place, which would delay and/or limit thunderstorm potential in
the afternoon, but a few model solutions are still somewhat
bullish with convection. Said stratus is currently variable as
far as bases but for the most part is remaining near or above 020
even during SHRA. Expect this to continue through the morning.
Smoke aloft will also persist today and may impact slantwise
visibility at times.

As for winds, they should gradually begin to favor a prevailing NE
and E direction through the morning, continuing through the
afternoon. Convective outflows may add greater variability to the
wind directions after ~18Z, with potential for brief gusts 25-35
kts at any of the terminals.

Fog/stratus potential is uncertain for tonight, with potential for
drainage flow to keep lower CIGS north of the terminals, but
there`s considerably variability in model guidance with this.

&&

.FIRE WEATHER...
Issued at 1252 AM MDT Thu Jun 25 2026

The fire weather environment will remain quite subdued through the
next 48 hours as a more moist airmass and accompanying
showers/thunderstorms provide a lull in fire danger for the
mountains. That being said, thunderstorms will be more numerous in
the high country today and, although these will be wet in nature,
may still pose a risk of fire starts given underlying drought and
fuel conditions.

This will become a greater concern come this weekend, when a much
drier, warmer and windier airmass will be in place. Southwest
winds will strengthen notably Saturday with sustained speeds in
the range of 20-30 mph for much of our higher elevations and
valleys, and higher gusts pushing 40-50 mph. Only a slight
moderation in wind and/or humidity is anticipated into Sunday and
Monday, such that critical fire weather conditions will be both
widespread and fairly prolonged. Any new fire starts, whether
lightning-induced or otherwise, will be susceptible to rapid
spread over the weekend. A Fire Weather Watch was issued for
Saturday given the high forecast confidence, and additional
highlights appear likely for the following day(s).

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch from Saturday morning through Saturday
evening for COZ211>214-217-218.

&&

$$

DISCUSSION...Rodriguez
AVIATION...Rodriguez
FIRE WEATHER...Rodriguez

NWS BOU Office Area Forecast Discussion