010
FXUS65 KBOU 251705
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1105 AM MDT Tue Jun 25 2024

.KEY MESSAGES...

- Continued Hot today with a Heat Advisory for the Denver Metro.

- Isolated high-based showers and thunderstorms this afternoon
  into the early evening with gusty winds.

- Slightly milder with increased chances for thunderstorms
  Wednesday and Thursday. A few could be strong to severe.

&&

.UPDATE...
Issued at 1105 AM MDT Tue Jun 25 2024

Temperatures this morning are running anywhere from 2-8 degrees
cooler across the I-25 corridor. Granted, it`s still going to be
hot across the entire area below 7,000 ft (> 90 degF), and the
current forecast highs still look well on track. We will leave the
Heat Advisory in place for metro Denver and at risk populations,
given temperatures at 11 AM are already at or above 90 degrees, on
their way to 97-100 degrees. Unlike yesterday when clouds and gust
fronts provided relief, today`s convection should be weaker and
with less coverage than on Monday, which will keep temperatures
hot well into the early evening hours, especially across Denver.
Larimer, Boulder, and Weld Counties will likely see some relief in
the form of clouds and cool-ish outflows by late afternoon.

&&

.SHORT TERM /Through tonight/...
Issued at 307 AM MDT Tue Jun 25 2024

Upper level high centered over the Central and Southern Rockies will
bring another very warm to hot day to the area. Highs over northeast
Colorado are expected to reach the mid to upper 90s. Winds turn
northerly by early afternoon, however the airmass with these
north winds won`t be much cooler, not at first anyways. Far
northeast Colorado, may see highs a couple of degrees cooler
today. A slight decrease in moisture and instability will lead to
fewer showers and thunderstorms. By mid afternoon, we should see
isolated showers and storms over the higher terrain. This activity
then drifts eastward through mid evening. Any rainfall reaching
the ground is expected to be brief and light. Wind gusts to 40 mph
will be common with the showers and storms. The showers/storms
dissipate this evening as the airmass stabilizes.

&&

.LONG TERM /Wednesday through Monday/...
Issued at 307 AM MDT Tue Jun 25 2024

The upper-level ridge will begin to show signs of deflation
Wednesday with slight cooling underneath. Fairly abundant mid-level
moisture will also be cycling clockwise into Colorado from the
Desert SW, pushing Precipitable Water (PW) values to 2-3 standard
deviations above normal later in the day. At the same time, a weak
and quasi-stationary boundary looks to hover over the plains, with
dewpoints likely breaking into the 60`s for the northeast plains
come the evening hours. Despite the comparatively cooler
temperatures, we`ll still be notably warm with high temperatures
that should climb into the lower to mid 90`s for the majority of our
lower elevations. Certainly sufficient to promote MLCAPE values in
excess of 1,000 J/Kg, mainly east of I-25. Of all the days in the
long-term forecast period, Wednesday looks like the one with the
most favorable bulk shear, enough to support some stronger storms,
some of which could become severe along and east of I-25 in the late
afternoon and evening, as well as produce locally heavy rainfall.

Flow aloft becomes more zonal Thursday. We`ll see a gradual
reduction in moisture, but PW values near or slightly above 1" still
seem plausible for most of the plains and urban corridor.
Temperatures will hold relatively steady and remain above average,
helped by development of weak downslope flow. Instability should be
slightly tapered relative to Wednesday, with the more favorable
parameter space located in the eastern plains. Storm motions also
look to pick up Thursday, closer to 20-30kt, which will help reduce
the threat of flash flooding for the burn scars. Nonetheless, at
least scattered thunderstorms appear a fair solution for most areas
in the afternoon.

A cold front associated with an upper-level shortwave will traverse
the region Friday, bringing modestly milder temperatures but also
slightly drier conditions. Afternoon thunderstorm coverage looks to
be somewhat reduced, with more isolated convection over the plains,
and higher storm potential over the higher terrain.

The weak downslope flow in place Friday is progged to dissipate by
Saturday and allow for temperatures to relax a little farther, as
highs descend closer to the mid 80`s for the plains. A few afternoon
thunderstorms can be expected again, most numerous in the mountains,
and with moisture on the rise, some of the stronger storms could
produce heavier rain.

With the ridge aloft pushing east of the region starting Sunday,
warm southeast surface flow will become more robust and help advect
more substantial low-level moisture into northeast Colorado, with
some guidance hinting at development of a dryline in the plains.
Hotter temperatures look slated to return as well, climbing back
into the 90`s. Isolated to scattered thunderstorms can be expected
again for much of the region.

&&

.AVIATION /18Z TAFS through 18Z Wednesday/...
Issued at 1105 AM MDT Tue Jun 25 2024

VFR through Wednesday and with hot temperatures both this
afternoon and Wednesday afternoon. There shouldn`t be any showers
at the terminals this afternoon, but one or two wind shifts with
gusty winds are expected. For now, the most likely wind shift
looks to be west, northwest, or north given where some weak
convection should be ongoing this afternoon. We will continue to
handle the potential wind shifts with a TEMPO group for VRB gusts
to 30 kts.

Tonight will be a normal drainage wind night (SSW at APA and DEN
8-12 kts; WSW at BJC 5-9 kts). On Wednesday, winds should shift to
the ESE and maybe gust over 20 kts from midday until storms gets
going and move of the mountains. Thunderstorm coverage will be
much more than that past couple of days. Those storms may directly
impact the terminals, but it`s about a 40 percent chance of a
storm going overhead. It`s almost a guarantee that several gust
fronts will move across the terminals with a wind shift and gusty
winds to 35 kts.

&&

.HYDROLOGY...
Issued at 307 AM MDT Tue Jun 25 2024

Increased subtropical moisture will be present Wednesday and
Thursday, boosting the potential for heavy rainfall from any
afternoon thunderstorms for all areas, including mountains and
plains. Storm motions will be slightly faster Thursday, helping to
taper the threat of flash flooding. Isolated to scattered
afternoon thunderstorms will continue beyond Thursday, but
moisture will generally be more limited, thereby reducing the
potential for heavier rainfall.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 9 PM MDT this evening for COZ040.

&&

$$

UPDATE...Schlatter
SHORT TERM...Meier
LONG TERM...Rodriguez
AVIATION...Schlatter
HYDROLOGY...Rodriguez