Flash Flood Warning 37, NWS Denver/Boulder, CO

217 
WGUS75 KBOU 270415
FFSBOU

Flash Flood Statement
National Weather Service Denver CO
1015 PM MDT Wed Aug 26 2026

COC001-005-039-270425-
/O.EXP.KBOU.FF.W.0037.000000T0000Z-260827T0415Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Adams CO-Arapahoe CO-Elbert CO-
1015 PM MDT Wed Aug 26 2026

...FLASH FLOOD WARNING HAS EXPIRED FOR ELBERT, ADAMS AND CENTRAL
ARAPAHOE AND EASTERN ARAPAHOE COUNTIES...

Flood waters have receded. Flooding is no longer expected to pose a
threat. Please continue to heed any remaining closures.

&&

LAT...LON 3977 10434 3976 10419 3977 10419 3972 10399
      3971 10379 3961 10371 3950 10371 3946 10374
      3941 10375 3939 10377 3938 10382 3939 10382
      3939 10386 3943 10400 3944 10400 3945 10405
      3946 10405 3949 10412 3967 10431 3972 10434
PARTITION...508005 608005

$$

MAI

Area Forecast Discussion
National Weather Service Denver/Boulder CO
616 PM MDT Wed Aug 26 2026

.KEY MESSAGES...

- Scattered afternoon/evening thunderstorms expected for the I-25
  Corridor and plains. A few storms could become severe, with
  large hail and strong winds possible.

- Thunderstorm coverage decreases Thursday and Friday with mainly
  isolated high-based showers/storms with gusty winds. 

- Temperatures return to the 90s Friday and Saturday across the
  plains. 

- Thunderstorm coverage increases for late Saturday and Sunday. 

&&

.DISCUSSION /Through Wednesday/...
Issued at 1140 AM MDT Wed Aug 26 2026

An upper level high will be centered over Arizona/New Mexico
today with ridging extending northward all the way to Alberta.
This will lead to a northwest flow aloft over Colorado. Outflow
from thunderstorms last night and this morning increased low level
moisture but also cooled the airmass. Temperatures are slow to
warm this morning, with 11 AM readings only in the mid to upper
70s. DEN ACARS soundings still show a strong inversion centered
around 700mb. Forecast model soundings show this as well, but they
don't appear strong enough regarding the inversion. This leads to
a highly uncertain thunderstorm forecast and severe threat for
later today. MLCAPE is still forecasted to climb to 1000-2000 J/kg
along and east of the I-25 corridor. The 0-6km bulk shear reaches
30-40 knots. The 30 knots is borderline for severe storms, but
where we see east to southeast surface winds around 10 knots, the
bulk shear will be closer to 40 knots. This favors areas east of a
line from Fort Collins to DIA for severe storms. Because of the
slower heating, storm development will likely be delayed with late
afternoon and early evening hours being favored. Again, given the
strength of the inversion, the severe thunderstorm threat remains
highly uncertain. 

The upper-level high will remain centered to our southeast, but
the ridge axis shifts eastward over Colorado on Thursday. This
will bring warmer temperatures and some drying. Precipitable water
values fall below an inch throughout the area, except for the far
eastern plains. Warmer air aloft, less moisture and instability
will lead to a notable decrease in thunderstorm activity. There
should be enough lingering moisture for isolated high-based
showers and thunderstorms. Any rainfall is expected to be light,
with gusty outflow winds up to 45 mph possible. However, southeast
winds will prevail over far eastern Colorado, helping to preserve
low level moisture. MLCAPE will reach 1000-2000 J/kg with 0-6km
bulk shear of around 40 knots, which would favor severe
thunderstorms. Warmer air aloft may cap convection, though.
Convergence along a boundary is likely needed for storms to
initially form, and models generally don't show this happening. 

The high intensifies (slightly) and drifts northeastward for
Friday. Temperatures warm further, with highs expected to reach
the lower to mid 90s across northeast Colorado. Models hint at a
slight increase in moisture, which should fuel a round of
afternoon/evening showers and thunderstorms. Given the warm
temperatures and limited moisture and instability, the
showers/storms are expected to be high-based with gusty outflows
being common.

For the weekend, an upper level trough (eventually strengthening
into a closed low) will track east across the northwest part of
the country. This will push the upper level high east of the
region, with southwest flow aloft developing over Colorado. We'll
see an increase in monsoon moisture leading to a better chance for
showers and thunderstorms.  The very warm air hangs on for
Saturday with lower to mid 90s expected again, but temperatures
will cool to the mid 80s to lower 90s for Sunday. 

The weather pattern for next week starts to look like a late
summer/early fall pattern, featuring stronger west to southwest
flow aloft with one or two shortwave troughs passing across the
region. For now, models show enough moisture each day for a round
of showers and thunderstorms. However, wouldn't be surprised if we
end up with a dry and breezy day due to subsidence behind an
exiting shortwave trough.  

&&

.AVIATION /00Z TAFS through 00Z Friday/...
Issued at 615 PM MDT Wed Aug 26 2026

Outside of brief thunderstorm impacts, VFR conditions are expected
to prevail through the TAF period. We've extended the TEMPO to 03Z,
as there is enough activity in the area currently to produce
outflows/microbursts well into the evening. Latest radar scans show
multiple outflows looking to move through KDEN's vicinity within the
next couple hours, creating the potential for showers/storms to form
over the airport. Should anything form directly over the airfield,
gusty winds up to 40kts and heavy rain with visibility reductions to
1-2SM are the main concerns. Once convection moves out of the area,
winds should turn south/southwest overnight before becoming variable
in the early morning hours, around 14-16Z, and then turning
northeast for the afternoon. There's a lot of uncertainty as far as
tomorrow's storm chances go. While confidence is low (10-20%) in
true shower/storm coverage over the area, the potential for outflows
with gusty winds remains, and so we've elected to keep the PROB30 in
the TAF for now.

&&

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

&&

DISCUSSION...BM
AVIATION...AGS

Special Weather Statement
National Weather Service Denver CO
224 PM MDT Wed Aug 26 2026

COZ037-262100-
Central and Southeast Park County CO-
224 PM MDT Wed Aug 26 2026

...A STRONG THUNDERSTORM WILL IMPACT SOUTHEASTERN PARK COUNTY UNTIL 3
PM MDT...

At 224 PM MDT, Doppler radar was tracking a strong thunderstorm near
Guffey, or 71 miles southwest of Denver, moving east at 10 mph.

HAZARD...Wind gusts up to 40 mph and half inch size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
  Guffey.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Monitor the weather situation closely and be alert for threatening
weather conditions.

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 3873 10564 3887 10557 3886 10533 3870 10533
      3870 10555
TIME...MOT...LOC 2024Z 287DEG 8KT 3879 10552

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...40 MPH

Aponte

Special Weather Statement
National Weather Service Denver CO
314 PM MDT Wed Aug 26 2026

COZ041-262145-
Elbert/Central and East Douglas Counties Above 6000 Feet CO-
314 PM MDT Wed Aug 26 2026

...A STRONG THUNDERSTORM WILL IMPACT WEST CENTRAL ELBERT AND
SOUTHEASTERN DOUGLAS COUNTIES UNTIL 345 PM MDT...

At 314 PM MDT, Doppler radar was tracking a strong thunderstorm near
Greenland, or 39 miles south of Denver, moving southeast at 10 mph.

HAZARD...Wind gusts up to 50 mph and penny size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
  Greenland.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Monitor the weather situation closely and be alert for threatening
weather conditions.

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 3916 10491 3927 10481 3923 10458 3913 10457
      3913 10489 3915 10491
TIME...MOT...LOC 2114Z 298DEG 8KT 3918 10478

MAX HAIL SIZE...0.75 IN
MAX WIND GUST...50 MPH

Aponte

Preliminary Local Storm Report
National Weather Service Denver CO
323 PM MDT Wed Aug 26 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0307 PM     Hail             3 ENE Greenland         39.21N 104.79W
08/26/2026  M1.00 Inch       Douglas            CO   Trained Spotter

&&

AGS

Preliminary Local Storm Report
National Weather Service Denver CO
614 PM MDT Wed Aug 26 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0505 PM     Hail             1 ESE Castle Pines      39.46N 104.86W
08/26/2026  M1.00 Inch       Douglas            CO   Public

&&

BR

Special Weather Statement
National Weather Service Denver CO
623 PM MDT Wed Aug 26 2026

COZ039-040-270100-
North Douglas County Below 6000 Feet/Denver/West Adams and
Arapahoe Counties/East Broomfield County CO-Boulder And Jefferson
Counties Below 6000 Feet/West Broomfield County CO-
623 PM MDT Wed Aug 26 2026

...A STRONG THUNDERSTORM WILL IMPACT SOUTHWESTERN DENVER...WEST
CENTRAL ADAMS...WESTERN ARAPAHOE AND NORTHEASTERN JEFFERSON COUNTIES
UNTIL 7 PM MDT...

At 623 PM MDT, Doppler radar was tracking a strong thunderstorm over
Wheat Ridge, or 10 miles west of Denver, moving east at 10 mph.

HAZARD...Wind gusts up to 50 mph and nickel size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
  Western Denver, Lakewood, Arvada, southern Westminster,
  southwestern Commerce City, Wheat Ridge, Golden, Edgewater and
  Mountain View.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Monitor the weather situation closely and be alert for threatening
weather conditions.

Heavy rain is occurring with this storm and may lead to flooding. Do
not drive your vehicle through flooded roadways.

&&

LAT...LON 3975 10524 3977 10522 3977 10521 3978 10520
      3979 10520 3980 10521 3986 10517 3984 10491
      3962 10506 3968 10519 3968 10515 3970 10514
      3970 10515 3972 10515 3973 10519 3973 10522
      3975 10523
TIME...MOT...LOC 0023Z 292DEG 10KT 3976 10513

MAX HAIL SIZE...0.88 IN
MAX WIND GUST...50 MPH

63