317
FXUS65 KBOU 091134
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
534 AM MDT Wed Jul 9 2025

.KEY MESSAGES...

- Hot today with highs brushing 100 degrees across much of the
  urban corridor and plains - Heat Advisory in effect.

- Elevated to locally critical fire weather conditions Thursday
  afternoon, with the greatest fire danger across South Park.

- Return to near-seasonal temperatures and scattered afternoon
  showers/thunderstorms Thursday onward.

&&

.DISCUSSION /Through Tuesday/...
Issued at 150 PM MDT Tue Jul 8 2025

Conditions thus far today have been almost a rinse and repeat from
Monday, albeit with slightly warmer temperatures and some
moderation in severe weather parameters. Low and mid-level lapse
rates remain very steep, on the order of 10 C/Km this afternoon,
with ACARS soundings showing DCAPE already exceeding 1,500 J/Kg at
KDEN. It`s thus no surprise we`ve seen some dry microburst
activity from early and very weak high-based showers, mainly
collocated with the area of lowest dewpoints across the southern
Denver metro. This elevated convection will continue trekking
eastward into the plains through the afternoon, encountering
modest instability with MLCAPE between 500-1,500 J/Kg, highest
closer to the Kansas state line. Deep layer shear isn`t as
pronounced as yesterday`s, but remains sufficient to support a few
stronger to marginally severe storms, with strong outflow gusts
to 60 mph and hail up to 1" being the main threats.

Our diurnal convection will take a break Wednesday as a ridge of
high pressure expands eastward over our area. Ample subsidence
beneath the right exit region of a jet streak, combined with a deep
well-mixed environment, will drive temperatures to around 10 degrees
above normal region-wide, with highs flirting with daily record
territory along the urban corridor. The current spatial extent of
the Heat Advisory appears well correlated to projected Heat Risk
and record potential, so no changes are planned to that headline.

The ridge will be short-lived, with an approaching shortwave on
Thursday bringing a quick return to mostly zonal flow. In fact, it
may arrive early enough to support a few morning convective showers
in the high country, mainly north of I-70. This shortwave will help
mitigate the heat, with highs cooling by 3-8 degrees Thursday, and
allow for a return of afternoon showers/thunderstorms to the high
country and, to a lesser extent, the lower elevations. Of note,
it looks as though moisture may struggle to reach Park County, where
dry near-surface conditions and good mixing may promote development
of critical fire weather conditions under gustier afternoon winds.
As such, have hoisted a Fire Weather Watch for South Park to
highlight this potential.

Flow aloft becomes more northwesterly by Friday, with another weak
shortwave progged to make an appearance later in the day and into
the overnight period. Afternoon thunderstorm chances will rise as a
result. Although instability doesn`t appear overly impressive, PWAT
values are slated to climb above 1" by Friday evening over the urban
corridor and portions of the plains, with some guidance even
suggesting as much as 1.2", which would be right around the
climatological maximum per SPC sounding archives. With the
possibility of some shallow upslope flow to boot, this opens the
door to the potential for evening and/or overnight convection east
of the foothills and some more efficient rainmakers.
Evening/overnight convection for the urban corridor has a tendency
to be sneaky, so have raised PoPs slightly to account for this
possibility.

Northwest flow will remain in place for Saturday with continued
chances of afternoon convection and near to slightly below-normal
temperatures. Some indication of ridge expansion and a trends
towards warmer/drier conditions for Sunday and Monday, but that`s a
ways out still.

&&

.AVIATION /12Z TAFS through 12Z Thursday/...
Issued at 534 AM MDT Wed Jul 9 2025

Mostly clear skies to prevail this morning. For this afternoon
(after 18Z Wednesday), some fair weather cumulus clouds above 10,000
feet are expected. As far as winds go, southerly winds to continue
until 14-15Z and then become light and variable. By 18Z, generally
north to northwest winds are expected and should continue through
Wednesday afternoon, but there will be some variability in the
direction. An outflow bringing northeast winds from storms over far
northeast Colorado will be possible after 00Z Thursday.

Mid and high clouds increase after 06Z Thursday as an upper level
system moves across Colorado. This should bring a westerly wind
shift 07-10Z Thursday, possibly gusty to 25 knots.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch from Thursday afternoon through Thursday
evening for COZ214.

Heat Advisory from 10 AM this morning to 9 PM MDT this evening
for COZ038>040.

&&

$$

DISCUSSION...Rodriguez
AVIATION...Meier