902
FXUS65 KBOU 050621
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1221 AM MDT Wed Aug 5 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 /06Z TAFS through 06Z Thursday/...
Issued at 1140 PM MDT Tue Aug 4 2026

Current observations show signs of a developing cyclone late
tonight. If this circulation continues to develop, winds will
likely remain light and variable with a gradual turning to the
north/northwest through the rest of the overnight hours. Guidance
has been persistent in showing low clouds and potential fog
developing once the northerly winds take hold. The most likely
timing remains consistent with the previous TAF package (10Z-14Z),
with considerable clearing expected between 14Z/15Z. There is
higher confidence in this outcome at KBJC/KDEN, but KAPA may hold
onto a more SW to W component for longer than the other TAF sites that
would keep fog to the north. The evolution of the cyclone will
continue to be monitored over the coming hours.

Smoke concentrations are expected to see some periods of
improvements throughout the day today, but there will still be
enough around for periods of lowered slant range vis. Smoke is
expected to increase at all levels again on Thursday morning,
with the higher concentrations sticking around through the day.

The cyclone is expected to move east of the TAF sites and wash out
by the early afternoon followed by a normal diurnal wind pattern
settling in for the afternoon and evening, with generally light
wind speeds expected through the TAF period.



&&

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

&&

$$

DISCUSSION...AP
AVIATION...9
FIRE WEATHER...AP

NWS BOU Office Area Forecast Discussion