438
FXUS65 KBOU 062101
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
301 PM MDT Sat Jun 6 2026

.KEY MESSAGES...

- Heating up today with isolated and gusty afternoon/early
  evening showers/storms.

- Critical fire weather conditions across portions of the plains
  today, with widespread critical fire weather conditions expected
  in fuel-prone areas by Tuesday and Wednesday.

- Hottest temperatures this weekend, and then again Tuesday and
  potentially Wednesday. Highs generally in the mid 90s across the
  I-25 Corridor and plains, but near 100 possible over the
  northeast plains Tuesday.

- Brief respite in the heat Monday, and then increasing heat
  relief late next week.

&&

.DISCUSSION /Through Saturday/...
Issued at 251 PM MDT Sat Jun 6 2026

Current water vapor imagery shows Colorado is currently sitting
between an upper-level low over TX/OK and an upper-level low
entering the Pacific Northwest this morning, placing Colorado on the
western side of an upper-level ridge. The main weather concerns for
today will be with developing critical fire weather conditions
across portions of the plains, and with gusty outflows from high-
based showers/storms. Things have taken a little longer to dry out
over the northeast plains after early morning fog, but relative
humidities are already moving towards the teens and winds are
simultaneously increasing. Today`s Red Flag Warning will continue
until 7 PM this evening when RH values are expected to increase to
above critical thresholds (More on fire weather in discussion
below). High temperatures are expected to be in the 90s across the
plains, and 70s to 80s in the mountain valleys.

We are already seeing convection form along the higher elevations
early this afternoon, with a boundary stretching from the Palmer
Divide northward across Douglas County and towards DIA that has
kicked up a few showers that are producing some gusty microbursts
but little precip. This is expected to be the outcome from most
showers that develop this afternoon as ACARS soundings show large
dewpoint depressions already in place, and forecast soundings show
inverted-v profiles (DALR up to 500mb), that would limit chances for
most precip to reach the surface. Hi-res guidance has persisted in
showing shower coverage expand this evening generally south and east
of the Denver area, so have increased PoPs to account for this
potential, with the greatest precip chances expected along and just
north of the Palmer Divide. We are expecting gusty outflows from
these with potential for some gusts to 50 mph.

For Sunday, hot temperatures are expected once again, but winds are
expected to slacken a bit across the lower elevations that would
limit any critical fire weather conditions from developing. The
approaching upper-level low over the Pacific Northwest is expected
to move eastward and into the Northern Rockies through the day and
lee troughing is expected to deepen as a response. This will enhance
compressional warming and we should see temps a few degrees warmer
than today`s. There should be enough mid-level moisture present to
see some afternoon showers, with the best chances for the
northeastern plains.

Monday will bring a slight cooldown, with afternoon highs expected
to drop back into the 80s for the urban corridor. A surface trough
is expected to increase low-level moisture and there will be enough
instability in place to allow for some afternoon convection.
Forecast soundings indicate enough MUCAPE (1200-1600 J/kg) and shear
(EBWD >30 kts) from increasing southwesterly flow aloft in place
for isolated strong to severe storms to develop, mainly for areas
east of I-25.

Tuesday and Wednesday are still on track to be hot, dry, and windy,
with critical fire weather conditions expected under well-above
normal temps. See Fire Discussion below for more details. Winds are
expected to increase with a strengthening pressure gradient both
aloft and at the surface. There are still some uncertainties with
the timing of an upper-level trough over the Northern Rockies, but
this will be the deciding factor on just how hot temperatures get on
both Wednesday and Thursday, as an associated cold front is
expected to drop south into Colorado. Latest guidance is trending
towards the faster trough ejection, which would move the hotter
temps to the east a little sooner, with near-normal temps
expected to end the week.


&&

.AVIATION /18Z TAFS through 18Z Sunday/...
Issued at 1221 PM MDT Sat Jun 6 2026

The TAFs are complicated today due to the continuation of weak of
convection over the mountains with possible initiation east
and/or south of Denver, but VFR conditions will prevail through
Sunday. Currently, convection over the Front Range mountains and
foothills is fairly weak. On shower generated a single flash of
lightning so far, and just 10-20% of lightning the rest of the
afternoon. This convection shouldn`t survive much as it moves
slowly east off the foothills. The exception could be BJC which is
why the PROB30 for SHRA is in place starting 19Z. The convection
and any gust front it produces is likely to shift winds to the
west at BJC this afternoon but once the gust front moves east of
BJC, convective potential becomes too low to mention in the TAF,
which will be after 22Z. DEN and APA have better chances of being
impacted by weak convection, and definitely by virga, but
probably not until after 21Z. The better chances of convection
impacting DEN and APA will be later this afternoon into the early
evening, with potential for gusts over 30 kts near any convection
that gets going. The winds will also be tricky at DEN and APA,
complicated by any convection. We don`t think any gust front from
the mountain/foothills convection will reach DEN, but convection
over the Palmer Divide, or convection that forms along a gust
front moving off the Palmer Divide could shift the winds from ESE
to S or SW at DEN and APA, again with gusts up to 30 kts. All this
detail is really hard to capture in the TAF, the best we could do
is the PROB30 for -SHRA and variable gusty winds to 35 kts. As
mentioned however, the most likely gust front wind direction would
be SW, S or SE this afternoon/evening. The other uncertain part
of the TAF are the SE winds after 02Z. Those winds in the model
output are forced by convection southeast of APA and DEN. The CAMs
all have some version of these winds and have for the last 6-7
runs, which is why we included them in the TAFs. However, if
convection doesn`t form, the SE winds won`t be as strong and we`ll
just see normal drainage winds out of the south 10-15 kts after
midnight.

Sunday looks like a very hot day but much lower chances of any
meaningful impacts from convection at any of the TAF sites. Winds
look to be WNW at 10 kts or so in the afternoon, and for now we do
not expect any gust fronts to form.

&&

.FIRE WEATHER...
Issued at 251 PM MDT Sat Jun 6 2026

A Red Flag Warning will remain in place until 7 PM this evening
across portions of the plains for low RH, gusty winds, and dry
lightning potential. Winds are expected to gradually increase
through the afternoon from east to west across the plains, with
gusts between 25-35 mph. Additional gusty winds will be possible
through the evening from outflows associated with showers/storms
(up to 50 mph possible).

For Sunday, we are expecting elevated fire weather conditions to
develop across the plains as RH values are forecast to drop into
the single digits to low teens in the afternoon. Winds are
expected to remain below critical thresholds for the majority of
the plains, but we are expecting winds to increase for our higher
mountains and valleys where fuels have yet to reach critical
dryness. No fire highlights are anticipated for Sunday.

We are still anticipating minimal fire weather concerns on Monday
as we see increased moisture and cooler temperatures, but things
will ramp up for the rest of the forecast period as winds are
expected to increase ahead of an approaching upper-level trough
amidst near record-high temperatures. HDWI still continues to show
Tuesday likely reaching above the 95th percentile and above the
90th for Wednesday. These are expected to be the two most critical
days for the majority of the forecast area as the forecast has RH
ranging from 8% to 12% (Tues) across all of the plains with
widespread 30-40 mph gusts, and 10-15% RH (Wed) with another day
of 30-40 mph gusts expected. There are still some uncertainties on
Thursday`s outcome with the timing of the approaching trough, but
critical fire weather conditions may persist, though there should
be some improvements to both RH and winds for Thursday, and the
HDWI does have the majority of its members dropping us down to the
below the 75th percentile.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 7 PM MDT this evening for COZ242>245-248.

&&

$$

DISCUSSION...9
AVIATION...Schlatter
FIRE WEATHER...9