National Weather Service Forecast Discussion

Thornton Weather Forecast   
Today's Forecast Story   
949
FXUS65 KBOU 211943
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
143 PM MDT Wed Oct 21 2026

.KEY MESSAGES...

- Warm and dry conditions continue across the lower elevations for
  the next few days, with scattered light rain and snow showers
  across the higher elevations.

- Cooler, more unsettled weather returns this weekend across the
  forecast area.

- At least a brief warm-up likely sometime early next week.

&&

.DISCUSSION /Through Wednesday/...
Issued at 131 PM MDT Wed Oct 21 2026

The upper level ridging over the area is moving east away from
the area today as an upper level trough begins to move onto the
West Coast. The upper trough will slowly progress eastward
towards the area through Friday. On Friday, models are showing a
piece of the trough breaking off and developing an upper low over
the Desert Southwest, while the parent trough moves off to our
northeast. This upper low is then expected to move towards our
area through the weekend. This means that we`ll stay in
south/southwest flow aloft through the end of the week, bringing
moisture into the area. Models are showing PW values around 200%
to 350% of normal for much of the area by Thursday. Southwest
winds tend to favor precipitation in SW Colorado, versus our
forecast area, but we could still see some weaker orographic lift
with this setup. With the influx of moisture we are expecting
precip chances to increase this evening in the higher terrain,
with showers continuing on and off through early Friday.

Temperatures will be well above normal through Friday, putting
snow levels around 12,000 to 13,500ft. So, most of the activity
over the next couple of days will likely be rain, with some snow
showers for our highest elevations. The better precip chances
will remain in the mountains, but CAMs are trying to bring some
showers onto the plains. There is potential for a Denver cyclone
tomorrow afternoon, which could allow for weak surface
convergence. This, along with the potential for a weak upper
disturbance, could be enough with the moisture present for a few
showers and storms in the plains Thursday afternoon and evening.

On Friday, 700mb to 500mb winds increase over the area. Mostly clear
skies and some QG subsidence could allow for these stronger winds
to mix towards the surface Friday afternoon. Winds gusts around
30 to 40mph are forecast along and south of I-76 and east of
downtown. A strong cold front will move into the CWA late Friday
into Saturday. The front will drop temperatures behind it, leaving
near to below normal highs for the weekend and early next week.
The secondary upper level trough is forecast to approach the area
Saturday and Sunday, moving over the area on Monday. Convergence
along the front and upper level support from the approaching
trough will bring higher rain chances for the plains this weekend.
Right now, the highest chance for heavier rainfall amounts is in
our southeastern counties, where moisture/PWs will likely be
higher.

Precip chances will decrease on Monday, with drier conditions
expected for the start of next week. Monday will mark the start of a
gradual warming trend, although there is potential for a front on
Wednesday to bring temperature back down a few degrees.

&&

.AVIATION /18Z TAFS through 18Z Thursday/...
Issued at 1208 PM MDT Wed Oct 21 2026

Current winds are light and variable over the Denver area with a
shift to the ESE expected in the next hour or so. Southeasterly
winds should pick up (~12KT) at around 21Z at KDEN and KAPA, with
much weaker speeds at KBJC. Southerly winds will begin to develop
over much of the CO plains and Denver metro in the evening, with a
light (

NWS BOU Office Area Forecast Discussion