907
FXUS65 KBOU 042341
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
541 PM MDT Tue Aug 4 2026

.KEY MESSAGES...

- Elevated to critical fire weather conditions likely across the
  high mountain valleys through the next few days.

- Cooler today and Wednesday before temperatures gradually warm
  back to the triple digits by next weekend.

&&

.DISCUSSION /Through Tuesday/...
Issued at 157 PM MDT Tue Aug 4 2026

Temperatures are much cooler this afternoon behind yesterday`s cold
front (around 30 degrees cooler than they were at this time
yesterday for the urban corridor and plains). Scattered showers
are expected in the South Park and Palmer Divide areas this
afternoon. Instability will be enough for an isolated thunderstorm
or two as well, but severe weather is not expected. The lower
levels are still pretty dry, so our main concern this afternoon
will be virga and gusty winds. Overnight, there is a low chance
for a few showers and storms in our far northeastern plains, as
some sort of weak surface trough sets up and there`s some low to
mid level convergence. We`ll see decent cooling overnight, with
below-normal lows in the upper 40s to mid 50s across the plains
in the morning.

Tomorrow, the warming trend begins again. The center of the upper
level high will push north and slightly east each day as we go
into Friday. Highs on Wednesday will warm around 5 to 10 degrees
compared to Tuesday. On Thursday, models have a boundary draped
across the eastern part of our county warning area from north to
south. Winds on the western side will be from the northwest and
winds on the eastern side will be from the southeast. There will
also be a significant moisture difference between the different
sides of the boundary, with much lower dewpoint to its west. The
weak downsloping and drier air will allow temperatures on the
west side of the boundary to increase into the mid 90s to around
100 degrees. Whereas the east side of the boundary, could be more
in the upper 80s to low 90s range. As for the smoke, the near
surface smoke from behind the cold front will continue to slowly
clear out of the area over the next day or two. Aloft, the NW
turning of the winds from the upper ridge building in, will give a
brief reprieve from the smoke moving in from Utah. However, with
continued NW winds, smoke from the Pacific NW will likely be moved
into the area aloft. So, we may not see a complete clearing of
the smoke for a while.

Temperatures for the weekend will continue to warm, as the ridge
sits over the area. For Saturday and Sunday, portions of the
plains around the I-25 and I-70 corridors have a medium to high
(50-80%) chance of reaching the triple digits each afternoon (with
lower chances in our southern counties). On Sunday, a weak upper
level disturbance could move through the flow aloft, bringing the
return of low end rain chances for the higher terrain.

&&

.AVIATION /00Z TAFS through 00Z Thursday/...
Issued at 534 PM MDT Tue Aug 4 2026

Winds have remained steady out of the east or northeast this
afternoon. This should continue into the evening with a gradual
turn to the southeast expected at DEN/APA.

Tonight`s forecast is still complicated. Most guidance develops a
weak Denver Cyclone sometime after 06z, with winds trying to turn
north/northwest at DEN/BJC. BUFKIT profiles at those two locations
would favor some fog development close to 12z Wednesday morning,
which has been hinted at across the last few HRRR/RAP cycles. For
now we`ve introduced some 3-5SM visby and FEW-SCT001 there but
will need to watch the evolution of any potential cyclone
overnight. It`s also unclear if smoke would further help to reduce
visibility... but would like contribute to additional slant range
visby issues at times.

Any fog should burn off quickly during the morning hours, with
winds eventually settling to a east-northeast direction again in
the afternoon. There could also be some gradual decrease in smoke
during the day, though I suspect slant range visby issues would
continue through sunset.

&&

.FIRE WEATHER...
Issued at 157 PM MDT Tue Aug 4 2026

A Red Flag Warning is in effect for North Park and Middle Park
this afternoon. Relative humidities are around 11% to 20% as of
early this afternoon with wind gusts around 20 to 35mph.
Humidities will start to increase and winds will start to decrease
around 5PM, rising above critical thresholds around 7PM. Winds are
expected to remain breezy tomorrow, with gusts around 20 to 35 mph in
the higher terrain. Tomorrow the dewpoints are expected to
decrease further, with the drier air expanding further east into
the higher elevations. Because of the continued strong winds and
expansion of the the low RHs, a Red Flag Warning was issued for
the mountain valleys and for elevations above 9000ft for tomorrow.

The drier air and lower dewpoints will continue to expand east
into the plains for Thursday and Friday. These lower dewpoints,
combined with a warming trend into the weekend, will bring
widespread 7% to 15% RHs for Thursday and Friday afternoons.
Winds will weaken slightly for Thursday in the higher terrain,
but we could still see elevated to critical conditions. In the
plains, winds look to generally remain below critical thresholds
for Thursday and Friday, but we could have some patchy near-
critical to critical conditions in the afternoons.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 7 PM MDT this evening for COZ211-213.

Red Flag Warning from noon to 7 PM MDT Wednesday for COZ211>214-
217-218.

&&

$$

DISCUSSION...AP
AVIATION...Hiris
FIRE WEATHER...AP

NWS BOU Office Area Forecast Discussion