951
FXUS65 KBOU 011656
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1056 AM MDT Fri Aug 1 2025

.KEY MESSAGES...

- Severe thunderstorms possible over the northeast plains late
  this afternoon and evening with 2 inch diameter hail and 70 mph
  winds possible.

- Some smoke is expected across the CWA today into this evening.

- Chance of thunderstorms gradually decreases into this weekend.

- Dry and hot early to mid portion of next week, with increasing
  fire danger Jackson and Grand Counties.

&&

.UPDATE...
Issued at 1055 AM MDT Fri Aug 1 2025

The 12Z Hi-Res models have come in all showing thunderstorms late
this afternoon and evening across the northeast Colorado plains.
Satellite imagery showing a good amount of stratocumulus clouds
over the northeast plains with temperatures in the lower 70s. It
becomes fairly unstable this afternoon with MLCAPE of 2000-3000
J/kg if we see surface temperatures in the lower 80s and dew
points in the upper 50s to lower 60s. Shear will be better today
than the past few days with 0-6km bulk shear of 30-40 knots. Given
decent moisture, instability, and shear, some of the storms
should become severe with large hail (slightly larger than golf
balls), and strong damaging winds to 70 mph. Increased
thunderstorm chances across the northeast plains for this.

Farther west, it will be drier with less shear and instability.
Scattered showers and thunderstorms are expected to develop by
early afternoon and then spread eastward. Brief heavy rain, small
hail, and wind gusts to 50 mph will be possible with the stronger
storms along the Front Range.

UPDATE Issued at 415 AM MDT Fri Aug 1 2025

This afternoon`s precipitable water values and surface dew points
look similar to yesterday`s numbers, as does the wind shear and
CAPE. There will be slightly better heating today. Models show a
fairly decent batch of convection starting up in the mountains in
the late morning, then pushing across the plains through about
04Z. With similar conditions expected, cannot rule out limited
flooding issues with a few of the storms as that has been the norm
the last few days over the eastern plains.  The smoke model shows
some areas of smoke today for the CWA coming from the Utah and
Arizona fires, however the model is trending with less smoke the
latest couple runs. I am not certain how much visibilities will
be restricted. Saturday warms up a bit and dries out somewhat.

Of note, there is still a Flood Advisory in effect until late
morning for eastern Adams and southwestern Morgan Counties from
late last evening`s heavy rains.

&&

.DISCUSSION /Through Thursday/...
Issued at 204 PM MDT Thu Jul 31 2025

Scattered thunderstorms have developed in the mountains as of
early afternoon. The main question surrounds how these will evolve
and/or survive eastward onto the plains. MLCAPE on the plains is
up to 1000-1500 J/kg, and should increase a bit more with further
daytime heating. CIN was still present on the plains, with a
maximum over the northern I-25 Corridor. ACARS soundings still
show a pretty healthy cap as well, but it is weakening with
further heating. CAMs are still showing scattered quasi-linear
type storms developing along the Front Range late this afternoon,
but with the amount of CIN still present (and some smoke limiting
daytime heating), there`s a considerable amount of uncertainty
whether these can get going along the northern I-25 Corridor. As a
result, the most likely area for initiation in the lower
elevations would be near the Wyoming border and Palmer Divide
where CIN is weakest. At this point, this puts northern Weld
County into the northern adjacent plains toward Sterling, Fort
Morgan, and Akron as being the most susceptible to any severe
storm development (both hail and damaging wind threat). Bulk
shear is greater up there, although storms over the Palmer Divide
could also produce strong winds. It`s not impossible the metro
area gets skipped over again with any significant storms, but
can`t rule that totally out either given some weak support by
glancing upper level disturbance moving into Wyoming and northwest
Colorado.

For Friday, the airmass will start to dry with precipitable water
values dropping back below normal. HRRR Smoke model shows
considerable smoke arriving from the fires in Utah and northern
Arizona, both thicker and higher concentration of near surface
smoke. Thus, we expect air quality to degrade further tomorrow.

Tomorrow will also start a prolonged drying and warming trend
which will last through the middle of next week. That is supported
by good ensemble agreement of strong ridging over Colorado
transitioning to more west/southwest flow aloft into the middle of
next week. This keeps a very dry airflow (Precipitable Water
dropping to 50% or less of normal) out of the Desert Southwest
and Great Basin, with little or no storm activity. This also
supports a strong warming trend especially by Tuesday and
Wednesday. Highs are likely to reach the mid to upper 90s across
the I-25 Corridor and plains, and a low probability (20%) of
reaching 100F. Fire danger concerns will also be increasing in
this period, mainly for the mountains and high valleys west of the
Front Range where strongest southwest flow is expected.

&&

.AVIATION /18Z TAFS through 18Z Saturday/...
Issued at 1055 AM MDT Fri Aug 1 2025

Smoke has increased this morning, but surface visibility is
expected to stay above 6SM. However, slantwise approach
visibility may be impacted and therefore added smoke to the TAF
through mid afternoon (21Z). The HRRR model (which did well
handling the increase in smoke this morning) decreases the smoke
mid to late afternoon. Will continue with the PROB30 for
thunderstorms, which looks on track. Gusty outflows producing wind
shifts are expected 21-02Z.

Other than possible smoke impacts, VFR conditions are expected
tonight and Saturday. Scattered thunderstorms are expected again
Saturday with about 30 percent chance for one near DEN, but
outflow winds will likely produce wind shifts after 19/20Z.

&&

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

&&

$$

UPDATE...Meier/RJK
DISCUSSION...Barjenbruch
AVIATION...Meier