National Weather Service Forecast Discussion

Thornton Weather Forecast   
Today's Forecast Story   
050
FXUS65 KBOU 022001
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
201 PM MDT Thu Jul 2 2026

.KEY MESSAGES...

- Critical fire weather conditions in South Park today and Friday.

- Isolated showers and storms will form mainly over east-central
  Colorado this afternoon and evening. A couple storms may be
  strong to severe.

- Near normal temperatures with scattered showers and storms on
  July 4th. These storms could become strong to severe.

&&

.DISCUSSION /Through Thursday/...
Issued at 1231 PM MDT Thu Jul 2 2026

As of 2pm this afternoon, there`s a boundary extending southeast from
south of Denver through Douglas and Elbert counties and into
southern Lincoln. Higher moisture and east/southeast winds are to
the north of the boundary and drier south/southwest winds are to
the south of the boundary. We`re already seeing some cumulus and
a thunderstorm develop along this boundary. Additional development
will be possible along this boundary into the late afternoon,
with activity then progressing to the northeast. Storms today
should remain relatively isolated. The most likely areas to see
storms today will be our southern and eastern counties, with a
chance for an isolated storm to move off the foothills and into
the northern I-25 corridor. Surface instability and shear along
the boundary could produce a landspout or two with any storm that
initiates along it. We`re also looking at the potential for large
hail and strong winds with any storm that develops.

Temperatures will increase for Friday as the upper level ridge
builds over the area. A weak upper level disturbance looks to
move near/north of the area Friday late afternoon and evening.
This combined with the potential for some residual outflow
boundaries from overnight convection to our north/northeast could
trigger some isolated convection. Most of the convection is
expected to remain to our north, however we could be on the tale
end of the activity, with a few storms pushing out of Wyoming and into
our northern counties. There`s still quite a bit of uncertainty
with the location and extent of the convection on Friday due to
the overnight activity tonight to our north, and it`s impact to
the afternoon convection in our area tomorrow.

Outflow from convection on Friday and more easterly surface winds as
a surface low moves near the area will bring increased moisture
and higher dewpoints for Saturday. The easterly/southeasterly
winds will allow for upslope flow, potentially triggering some
showers and thunderstorms in the early to mid afternoon, with
storms progressing east into the evening. The east/southeast
surface winds and westerly winds aloft will create decent 0-6km
shear across the area. This combined with strong lapse rates could
lead to severe weather Saturday afternoon and evening. The main
hazards will be large hail, strong winds, and dangerous lightning.

Upper level ridging will build over the area Sunday into early
next week, bringing temperatures into the low to mid 90s across
the plains. Even with the strengthening ridge, a few upper level
disturbances are expected to move through the flow aloft,
bringing the potential for isolated showers and storms each
afternoon Sunday and Monday. The ridge will start to push eastward
on Tuesday, flattening a bit as a more potent shortwave moves
through. This shortwave will provide the potential for more
widespread rain Tuesday afternoon and evening.

&&

.AVIATION /18Z TAFS through 18Z Friday/...
Issued at 1151 AM MDT Thu Jul 2 2026

Winds are just now transitioning to diurnal easterlies, and should
gradually strengthen with a shear zone/weak cyclone developing
south of the TAF sites. Peak gusts could reach 20-22 kts. There is
already some high based cumulus southwest of the TAF sites, and
given that we expect some isolated virga we`ve introduced a
PROB30 of VRB gusty outflow winds. DCAPE is nearly off the charts
given the deep and dry subcloud layer, reaching 1600-1700 J/kg so
potential for very localized gusts to 50 kts if we fully mix, but
that`s also the greatest uncertainty as we`re still quite stable
with delayed heating after last night`s surge. Winds may very well
become VRB for a few hours 03Z-06Z if we get any convective
influence, but will otherwise lean toward a fairly normal diurnal
wind progression from SE-SSW-WSW 03Z-12Z Friday. Then back to a
diurnal easterly around 18Z-19Z Friday.

Next concern is smoke impacts. We still have marginal IMC
conditions at the start of this TAF period, but additional smoke
will arrive from the wildfires in southwestern Colorado and
southeast Utah. With the change in trajectories, smoke
concentration will be greater than the last few days and thus
could actually start impacting visibility down to ~6SM at times
through 18Z Friday.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 8 PM MDT this evening for COZ214.

Red Flag Warning from noon to 7 PM MDT Friday for COZ214.

&&

$$

DISCUSSION...AP
AVIATION...20

NWS BOU Office Area Forecast Discussion