427
FXUS65 KBOU 081125
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
525 AM MDT Tue Jul 8 2025

.KEY MESSAGES...

- Fewer showers and thunderstorms this afternoon/evening, mostly
  over the eastern plains. Gusty outflow winds to 50 mph will be
  the main threat, however a few severe gusts to 60 mph can`t be
  ruled out.

- Very hot temperatures expected Wednesday with the upper 90s to
  low 100s expected across the I-25 corridor and plains. It is
  possible the hot temperatures extend into Thursday.

- Cooler Friday into the weekend with a chance of storms.

&&

.UPDATE...
Issued at 227 AM MDT Tue Jul 8 2025

Upper level high will build over the Central Rockies today and
Wednesday bringing very warm to hot conditions. Airmass also dries
some with precipitable water values falling to 0.50-0.75 (in)
across the Front Range and nearby plains. This is 60-75% of
normal. Isolated showers/storms will be possible this afternoon
with gusty outflow winds to 50 mph possible. Also, can`t rule out
a stray 60 mph gusts as well. Moisture and instability will be
better over the eastern plains (east of Limon to Sterling line).
Here storms could be stronger with brief heavy rain and small hail
in addition to the gusty winds.

&&

.DISCUSSION /Through Monday/...
Issued at 244 PM MDT Mon Jul 7 2025

The strength of today`s storms was known right away as a
microburst produced 70 mph winds a couple miles west of
Centennial Airport and 66 mph winds at the ASOS sensor at
Centennial Airport. Very steep lapse rates and DCAPE values around
1,700 j/kg indicate that these type of winds (60-70mph) will be
possible across the I-25 corridor and eastern plains this
afternoon and early evening. In addition, storms to the east of a
line from Fort Morgan to Limon will be able to tap into better
instability (surface based CAPE values 2,000-3,000 j/kg) to
produce large hail greater than an inch in diameter. The only
limiting factor to severe storms is the weak, but sufficient, deep
layer shear with values are around 30-35 knots in the northeast
corner of Colorado. A Severe Thunderstorm Watch was issued for all
areas east of I-25 until 9pm this evening.

On Tuesday, warmer and drier air aloft will move into Colorado
along with rising 500 mb heights. Across the Cheyenne Ridge and
Palmer Divide, some lingering moisture and slight convergent flow
may be enough for a few storms to develop. Overall coverage of
showers and storms should be about 20 percent so PoPs are around
that threshold. High temperatures across the plains will warm up
to the mid 90s.

The axis of an upper level ridge will be over Colorado on
Wednesday. 500 mb heights will be flirting with 597 dm in our
forecast area. There will be an upper level jet streak over
northern Utah and Wyoming that will position our forecast area
under the right exit region with subsident flow. All factors look
to great compressional warming and near record highs are forecast
as a result. There was an office discussion about whether to issue
a Heat Advisory. A few factors were considered with a main factor
being the HeatRisk is forecast to be 3 for Denver, Boulder, and
Fort Collins. Given the heat may break records (record highs in
Denver, Boulder, and Fort Collins are 100, 99, and 99 respectively
with the forecast highs of 99, 99, and 100 respectively) and
there will be minimal cloud cover along with light winds, the
decision was made to issue a Heat Advisory for zones 38, 39, 40
(Fort Collins, Boulder, and Denver). The decision was made to hold
off on an advisory for Greeley and other areas farther east since
temperatures will be a few degrees below records. For example,
the record high in Greeley is 105 with a forecast of 101.

A quick moving shortwave trough will push through our forecast
area midday Thursday. With warm air aloft, temperatures will
still be quite warm with highs in the mid to upper 90s across the
plains. With this trough, winds will likely increase and it may
lead to elevated fire weather conditions with relative humidity
dropping to as low as 10 percent and gusts around 25 mph.

Cooler conditions and a chance of scattered storms will return on
Friday as a cold front moves through.

&&

.AVIATION /12Z TAFS through 12Z Wednesday/...
Issued at 525 AM MDT Tue Jul 8 2025

Winds will be light and variable this morning as they transition
to a northerly direction this afternoon (after 18Z). Isolated
high- based afternoon showers/storms are expected with the best
time frame 20-23Z. Gusty outflow winds producing wind shifts will
be the main threat. The showers/storms are expected to be east of
the Denver area by 00Z Tuesday. As far as winds go this evening,
easterly winds turn southeast and then eventually southwest late
this evening and overnight.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from 10 AM to 9 PM MDT Wednesday for COZ038>040.

&&

$$

UPDATE...Meier
DISCUSSION...Danielson
AVIATION...Meier