Flash Flood Warning 31, NWS Denver/Boulder, CO

006 
WGUS75 KBOU 152327
FFSBOU

Flash Flood Statement
National Weather Service Denver CO
527 PM MDT Sat Aug 15 2026

COC123-160115-
/O.CON.KBOU.FF.W.0031.000000T0000Z-260816T0115Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Weld CO-
527 PM MDT Sat Aug 15 2026

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 715 PM MDT THIS
EVENING FOR NORTHEASTERN WELD COUNTY...

At 527 PM MDT, Trained weather spotters reported flash flooding 10
miles west of Westplains, with a significant amount of water running
across Highway 71. Between 1.5 and 3 inches of rain have fallen.
Flash flooding impacts will continue, but no additional rainfall is
expected.

HAZARD...Flash flooding caused by thunderstorms.

SOURCE...Trained spotters reported.

IMPACT...Flash flooding of small creeks and streams, gulches, roads,
         and poor drainage and low-lying areas.

Some locations that will experience flash flooding include...
  Mainly rural areas of Northeastern Weld County.

This includes the following streams and drainages...
  Spring Creek, Twomile Creek, Horsetail Creek, Cottonwood Creek,
  Sidney Draw, George Creek and North Pawnee Creek.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Move to higher ground now. Act quickly to protect your life. Do not
drive through flooded areas.

Excessive runoff from this storm will cause flash flooding of small
creeks and streams, country roads, farmland along creeks, and other
low lying areas.

&&

LAT...LON 4098 10357 4090 10362 4087 10366 4079 10359
      4077 10361 4082 10387 4100 10376 4100 10357

FLASH FLOOD...OBSERVED
EXPECTED RAINFALL RATE...1.5-3 INCHES IN 1 HOUR

$$

20

792 
WGUS75 KBOU 160118
FFSBOU

Flash Flood Statement
National Weather Service Denver CO
718 PM MDT Sat Aug 15 2026

COC123-160128-
/O.EXP.KBOU.FF.W.0031.000000T0000Z-260816T0115Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Weld CO-
718 PM MDT Sat Aug 15 2026

...FLASH FLOOD WARNING HAS EXPIRED FOR NORTHEASTERN WELD COUNTY...

The heavy rain has ended and flood waters have receded. Flooding is
no longer expected to pose a threat. Please continue to heed any
remaining closures.

&&

LAT...LON 4098 10357 4090 10362 4087 10366 4079 10359
      4077 10361 4082 10387 4100 10376 4100 10357

$$

20

Area Forecast Discussion
National Weather Service Denver/Boulder CO
112 PM MDT Sat Aug 15 2026

.KEY MESSAGES...

- Another round of showers and thunderstorms this afternoon and
  evening. Heavy rainfall and flash flooding are the main threats
  today. A few thunderstorms could become severe, with strong
  winds and hail possible.

- Monsoon moisture lasts through Sunday, bringing scattered
  showers and thunderstorms again tomorrow.

- Warming and drying trend for Monday and Tuesday.

- Another active day possible middle of next week.

&&

.DISCUSSION /Through Saturday/...
Issued at 103 PM MDT Sat Aug 15 2026

The wetter weather pattern will continue on through this weekend.
For today, there is a risk for severe weather and flash flooding.
The eastern plains should be located near the right entrance region
of a jet over the central US with a small disturbance expected in
the flow aloft. GOES-19 satellite imagery shows a cirrus shield
currently over the mountains that could initially inhibit convective
development. Nevertheless, convective development is starting to
occur across the foothills and in Larimer county. We expect showers
and thunderstorms to develop across the foothills early this
afternoon and move into the I-25 corridor by mid-to-late afternoon.
These storms will then move off to the east in the late afternoon
and early evening.

The previously mentioned cirrus shield could hinder rain coverage
and/or push this timing a bit later. The biggest threat for today
will be heavy rainfall with some episodes of flash flooding possible
across the area. The Weather Prediction Center highlights the
foothills, I-25 corridor, and the eastern plains in a slight (2/4)
risk for excessive rainfall for today. Several ingredients are in
place for this threat. Thus, a Flood Watch is in effect from 2pm to
10pm this afternoon and evening. See the hydro discussion for more
details.

The Storm Prediction Center highlights the plains in a
slight (2/5) risk. MLCAPE values are forecast to be around 1000-1200
J/kg and 0-6 km shear will be around 30-40 kts. Large hail and
damaging winds are possible from storms today, with the highest
chances along the Palmer Divide.

Tomorrow will bring similar threats as today, though we expect less
coverage of thunderstorms. Thus, the threats will be more localized
in nature. MLCAPE and bulk shear values are forecast to be lower
than today. The highest chances for showers and thunderstorms
tomorrow should stay along/near the Palmer Divide, but there will
still be scattered storms possible for most of our plains.

High pressure will shift closer to our area for Monday and Tuesday
further lowering rain chances and raising temperatures to around
90 degrees for the plains. By Wednesday, high pressure should
shift off to the southwest, opening the door for a disturbance to
move through the flow aloft and bringing back some isolated to
scattered rain chances. This will only be a brief break as high
pressure will start to build over the Four Corners region.
Temperatures are expected to return to the low to mid 90s across
the plains for the end of the week and into next weekend.

&&

.AVIATION /18Z TAFS through 18Z Sunday/...
Issued at 1243 PM MDT Sat Aug 15 2026

Current radar imagery shows scattered showers and thunderstorms
developing over the foothills and moving east. We have opted to
include PROB30s at all three airports to reflect the chance for a
isolated storm or erratic gusty outflow in the vicinity before
21Z, when the primary threat window begins. Lightning and winds
gusting up to 40KT will be the main concern, although rainfall
rates could be heavy enough to cause some visibility reductions
(2SM-4SM) if the core of a storm tracks over the airport. Showers
and storms may linger until 03Z, particularly if outflows over the
eastern plains initiate additional storms near KDEN and KAPA.

Winds will turn light and variable late this evening before a very
weak S-SW drainage flow takes shape around 06Z. There is a 40%
chance that low stratus and/or fog from the northeast CO plains
makes it to the Denver metro, with the better chance at KDEN and
KBJC. We have decided to keep low ceilings out of the TAFs for now
due to uncertainty, but changes may need to be made in the next TAF,
particularly if guidance continues to suggest very weak or variable
surface winds all night. There will be another chance for isolated
showers and storms Sunday afternoon, between 21Z and 00Z.

&&

.HYDROLOGY...
Issued at 103 PM MDT Sat Aug 15 2026

Several ingredients are in place for the excessive rainfall
threat today. PWATs values will be around 150% of normal. Warm cloud
layer heights will approach 5000 feet, allowing for rather efficient
warm rain processes. Easterly (upslope) winds are occurring which is
continuing to advect moisture into the area. Dewpoints should be in
the 50s for the I-25 corridor and low to mid 60s across the plains
this afternoon and evening. Significant portions of our area have
received 2 to 5 inches over the last 3 days, lowering flash flood
guidance. Although, storm motions should be a touch faster than
yesterday- around 20-25 kts. Any storms today could produce 1 to 2
inches in 30 minutes. Rainfall totals for today could be in excess
of 2 to 4 inches. Given the nature of these storms, there will be
varying rainfall totals across short distances. A Flood Watch is in
effect from 2pm to 10pm this afternoon and evening.

For tomorrow, moisture is expected to decrease- PWATs will drop to
about 100 to 125% of average. The flooding risk for tomorrow will be
lower than today and more isolated in nature. The Weather Prediction
Center only highlights the Palmer Divide in a slight (2/4) risk for
excessive rainfall for tomorrow, where storm coverage should be
highest.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Flood Watch until 10 PM MDT this evening for COZ036-038>051.

&&

DISCUSSION...MV
AVIATION...AA
HYDROLOGY...MV

Special Weather Statement
National Weather Service Denver CO
208 PM MDT Sat Aug 15 2026

COZ039>041-152045-
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-Elbert/Central
and East Douglas Counties Above 6000 Feet CO-
208 PM MDT Sat Aug 15 2026

...A LINE OF STRONG THUNDERSTORMS WILL IMPACT SOUTHWESTERN DENVER...
SOUTHWESTERN ADAMS...WESTERN ARAPAHOE...NORTHWESTERN ELBERT...
NORTHEASTERN JEFFERSON AND NORTHEASTERN DOUGLAS COUNTIES UNTIL 245 PM
MDT...

At 208 PM MDT, Doppler radar was tracking a line of strong
thunderstorms extending from over Lakewood to over Castle Rock, or
extending from 11 miles west of Denver to 23 miles south of Denver,
moving northeast at 10 mph.

HAZARD...Wind gusts up to 50 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...
  Denver, southwestern Aurora, Lakewood, southeastern Arvada,
  Centennial, Highlands Ranch, Castle Rock, Parker, Littleton,
  Englewood, Wheat Ridge, Greenwood Village, Lone Tree, Sheridan,
  Morrison, Castle Pines, The Pinery and Franktown.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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

&&

LAT...LON 3968 10478 3943 10465 3933 10490 3952 10496
      3962 10516 3965 10519 3968 10519 3968 10516
      3969 10514 3971 10515 3972 10516 3984 10509
TIME...MOT...LOC 2007Z 223DEG 9KT 3970 10515 3956 10492 3940 10484

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...50 MPH

63

Preliminary Local Storm Report
National Weather Service Denver CO
224 PM MDT Sat Aug 15 2026

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

0219 PM     Hail             2 SSW Foxfield          39.57N 104.80W
08/15/2026  E1.75 Inch       Arapahoe           CO   Public

            Some hail of up to golf ball size.

&&

Preliminary Local Storm Report
National Weather Service Denver CO
227 PM MDT Sat Aug 15 2026

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

0216 PM     Tstm Wnd Gst     3 NE Lone Tree          39.56N 104.85W
08/15/2026  M64 MPH          Douglas            CO   AWOS

            AWOS station KAPA 2 SSE Centennial.

&&

Special Weather Statement
National Weather Service Denver CO
326 PM MDT Sat Aug 15 2026

COZ043-044-152200-
Morgan County CO-Central and South Weld County CO-
326 PM MDT Sat Aug 15 2026

...A STRONG THUNDERSTORM WILL IMPACT NORTHWESTERN MORGAN AND
SOUTHEASTERN WELD COUNTIES UNTIL 4 PM MDT...

At 326 PM MDT, Doppler radar was tracking a strong thunderstorm 8
miles north of Riverside Reservoir, or 24 miles northwest of Fort
Morgan, moving east 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...
  Jackson Reservoir and Goodrich.

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 4035 10427 4051 10425 4052 10402 4035 10404
TIME...MOT...LOC 2126Z 269DEG 9KT 4043 10419

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

63

Preliminary Local Storm Report...Summary
National Weather Service Denver CO
401 PM MDT Sat Aug 15 2026

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

0310 PM     Flash Flood      1 S Aurora              39.68N 104.81W
08/15/2026                   Arapahoe           CO   Public

            Large amount of running water at Nicks
            Garden Center. Video from social media.

0304 PM     Flood            1 WSW Arapahoe Park     39.63N 104.70W
08/15/2026                   Arapahoe           CO   Trained Spotter

            Moving water with unknown depth Spotter
            Number: AR1706.

0303 PM     Flash Flood      1 E Lone Tree           39.54N 104.86W
08/15/2026                   Douglas            CO   Law Enforcement

            South Metro Fire and Douglas County Sheriff
            are responding to stranded motorists in
            Meridian Village at multiple flooded
            intersections. Photos on social media show
            water above the tires of a car.

0255 PM     Flash Flood      4 W Aurora              39.70N 104.88W
08/15/2026                   Denver             CO   Broadcast Media

            Video relayed through broadcast media shows
            6-8 inches of moving water on the roadway.
            Time estimated from radar.

0255 PM     Flash Flood      3 W Aurora              39.70N 104.87W
08/15/2026                   Denver             CO   Public

            Video on social media showing an estimated 6
            inches of running water on the roadway.

0246 PM     Flash Flood      3 E Cherry Creek Reserv 39.64N 104.82W
08/15/2026                   Arapahoe           CO   Trained Spotter

            Estimated 1 foot of water over the roadway
            Spotter Number: AR1307.

0232 PM     Flood            2 NE Cherry Creek Reser 39.66N 104.84W
08/15/2026                   Arapahoe           CO   Trained Spotter

            Around 2 inches of water on the roadway.
            Spotter Number: AR1307.

&&

Special Weather Statement
National Weather Service Denver CO
402 PM MDT Sat Aug 15 2026

COZ042-048-152245-
Logan County CO-Northeast Weld County CO-
402 PM MDT Sat Aug 15 2026

...A LINE OF STRONG THUNDERSTORMS WILL IMPACT NORTHWESTERN LOGAN AND
NORTHEASTERN WELD COUNTIES UNTIL 445 PM MDT...

At 402 PM MDT, Doppler radar was tracking a line of strong
thunderstorms extending from 11 miles south of Kimball Municipal
Airport to 10 miles east of Pawnee Buttes, or extending from 14 miles
south of Kimball to 30 miles south of Kimball, moving east 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...
  Westplains.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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

&&

LAT...LON 4079 10385 4094 10374 4100 10371 4100 10346
      4090 10349 4078 10351
TIME...MOT...LOC 2201Z 273DEG 10KT 4103 10365 4091 10368 4081 10378

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

63