117
FXUS65 KBOU 251124
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
524 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.

&&

.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 /12Z TAFS through 12Z Wednesday/...
Issued at 524 AM MDT Tue Jun 25 2024

Southerly drainage winds to prevail at DEN and APA through early to
mid morning (14-16Z). Winds then transition to a northerly direction
by 18Z and a for most of Tuesday afternoon. High based gusty showers
develop after 20Z Tuesday, with a wind shift or two possible.
Chances for a weak thunderstorm are low, about 10 percent. Threat
for showers and wind shifts end 03-06Z with southerly drainage winds
kicking in. Around or a little after 12Z Wednesday, winds turn
northerly in response to a Denver Cyclone. There`s a slight chance
(10-20%) for low clouds after 12Z Wednesday at DEN and APA. There
will be a better chance for low clouds at FNL and GXY.

&&

.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.

&&

$$

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