888
FXUS65 KBOU 291910
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
110 PM MDT Sun Jun 29 2025

.KEY MESSAGES...

- Cooler today and Monday with higher coverage of storms and a
  threat for some of the storms to be strong to severe.

- Scattered thunderstorms and normal temperatures are expected for
  the Fourth of July.

&&

.UPDATE...
Issued at 230 AM MDT Sun Jun 29 2025

There are some mixed signals as to tstm potential this aftn into the
early evening hours.  HRRR is very aggressive in developing tstms
along the I-25 Corridor by mid aftn and then moving these storms
eastward across the far ern plains by early evening.  Meanwhile,
other hi res data keeps most of the tstm activity mainly along the
foothills and I-25 Corridor and don`t spread these storms as very
far eastward.  There will be a front moving across nern CO later
this morning and aftn. Thus this could be one reason why some of
the hi res data is keeping the storms focused along the I-25
Corridor as the plains become more stable behind the front.
Overall, confidence isn`t high as to what may evolve this aftn
into the early evening hours. MLCAPE may reach the 1500-2000 j/kg
depending on how much low level moisture comes in behind the
front. Thus, with a favorable shear profile there will be a
threat of a few svr storms.

For tonight, there are varying solutions as to the potential of
nocturnal tstms over portions of the nern plains late tonight.  Nern
CO will be near the right exit region of an upper level jet, so
it`s not impossible there could be some late night tstm
development closer to the WY-NE border area. Intensity of the
storms will likely depend on amount of available instability.

&&

.DISCUSSION /Through Saturday/...
Issued at 253 PM MDT Sat Jun 28 2025

Visible satellite shows two areas of storms in our forecast area
with one being in Lincoln County and another in Logan County.
These storms could produce strong wind gusts up to 55 mph given
the steep low level lapse rates and DCAPE values close to 1,800
j/kg on the SPC mesoanalysis page. The most likely location for
strong winds are in Phillips and Sedgwick Counties as storms will
have the best surface based CAPE there. Elsewhere, showers and
storms are struggling to form given the warm air aloft and
subsident flow. There will still likely be some virga that forms
which could produce dry microbursts with winds close to 45 mph
over the I-25 corridor.

There is currently a cold front in northeast Wyoming that will
help to generate an MCS this evening in Wyoming and eastward. The
combination of the cold front and outflow winds from the MCS will
move southward into northeast Colorado early Sunday morning.
Northeast winds will continue throughout the day across the plains
with healthy moisture arriving with dew points in the upper 50s.
Mixed-layer CAPE values will reach around 2,000 j/kg indicating
moderate instability. As for shear, upper level winds will be
lacking with speeds only around 25-30 knots at 500 and 250 mb. So
deep layer shear will only be about 30-35 knots. Given those
parameters, a few strong to severe storms are expected to form but
it will not be a widespread severe outbreak. Large hail and
damaging wind gusts will be the primary threats and an upgrade to
an SPC slight risk may be warranted.

Some high resolution models are indicating that strong storms
could form during the overnight hours Sunday night given the
moderate elevated instability and a weak shortwave moving through
aloft. This overnight convection will depend on how much
convection occurs during the day on Sunday. If there are very few
storms and the instability is untapped, there may be scattered
coverage of strong storms across the northeast plains. However,
if there are more numerous storms Sunday afternoon, the chance for
overnight convection will be much lower.

On Monday, temperatures will be well below normal across the I-25
corridor and eastern plains due to upslope winds and low level
clouds. Highs may not even reach 80 across the plains. This setup
of easterly winds with good moisture favors widespread storms over
the southern foothills and Park County. There are likely PoPs in
those areas and rainfall totals could exceed 1 inch. Elsewhere,
conditions look capped, especially near DIA and areas to the north
and east of the airport.

The center of a ridge aloft will be over Colorado on Tuesday and
Wednesday. Highs will warm up closer to normal and convection will
stay mostly over the higher terrain given the very weak steering
flow aloft and more stable conditions east of I-25.

A trough over the Las Vegas area and a ridge over the central US
will help to draw up moisture from the tropics on Thursday and
Friday. Precipitable water values may increase to over an inch in
Denver on Friday. Depending on the timing of a shortwave passage,
the Fourth of July has the potential to be a wet day with
scattered to numerous thunderstorms possible.

&&

.AVIATION /18Z TAFS through 18Z Monday/...
Issued at 1235 PM MDT Sun Jun 29 2025

Showers and storms are already forming over the higher terrain
today but they will initially struggle to move onto the plains due
to a strong inversion. By the mid afternoon, strong storms will
push across the Denver metro with hail and strong wind gusts
possible. All terminals will likely be impacted and gusts could
reach 50 knots. Once the storms pass through, winds will become
easterly for the evening.

Overnight tonight, there will be light drainage flow. By 08-11Z, a
push of northerly winds are expected to bring in a stratus deck
with ceilings around 1,000-2,000 feet. There is a 30% chance that
only a scattered layer develops instead of a broken layer. This
broken stratus layer will likely dissipate between 16-18Z tomorrow
morning.

Given the cool temperatures and stable conditions tomorrow, DEN
and BJC are expected to be dry and not be impacted by storms. APA
may receive an outflow boundary from storms over the southern
foothills.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

UPDATE...RPK
DISCUSSION...Danielson
AVIATION...Danielson