411
FXUS65 KBOU 072129
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
329 PM MDT Mon Jul 7 2025

.KEY MESSAGES...

- Scattered afternoon/evening thunderstorms today, most numerous
  over the eastern plains. Some strong to severe storms are
  possible with large hail and damaging wind gusts, mainly across
  the eastern plains.

- 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.

&&

.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 /18Z TAFS through 18Z Tuesday/...
Issued at 1217 PM MDT Mon Jul 7 2025

VFR conditions expected through the TAF period. Isolated/scattered
afternoon thunderstorms are expected to develop this afternoon
with the best coverage east of DEN. Strong outflow winds
producing wind shifts will be the main threat with gusts up to 40
knots possible if a storm were to move over the terminal. High
resolution models are beginning to converge on a solution that
takes a strong outflow from storms over the eastern plains
through all three terminals around 00-01Z with easterly winds
with gusts up to 35 knots. Therefore, the PROB30 was extended to
01Z this evening.

There will be much drier conditions on Tuesday and no storms are
expected to make a direct impact on the terminals. However, the
steep lapse rates and large DCAPE will allow storms to create
gusty winds and outflow boundaries. Therefore, a PROB30 was once
again included since a chance of an outflow boundary coming
through is at roughly 20-30%.

&&

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

&&

$$

DISCUSSION...Danielson
AVIATION...Danielson