Flash Flood Warning 30, NWS Denver/Boulder, CO

128 
WGUS75 KBOU 152104
FFSBOU

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

COC001-005-031-152345-
/O.CON.KBOU.FF.W.0030.000000T0000Z-260815T2345Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Adams CO-Arapahoe CO-Denver CO-
304 PM MDT Sat Aug 15 2026

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 545 PM MDT THIS
AFTERNOON FOR ADAMS, WESTERN ARAPAHOE AND DENVER COUNTIES...

At 304 PM MDT, Doppler radar indicated thunderstorms producing heavy
rain in Water was flowing 1 foot deep at Quincy and Smoky Hill Road.
Between 1.5 and 3 inches of rain have fallen. The expected rainfall
rate is 1.5 to 3 inches in 45 minutes. Additional rainfall amounts up
to 1 inch are possible in the eastern portions of the warned area.
Flash flooding is already occurring.

HAZARD...Life threatening flash flooding. Thunderstorms producing
         flash flooding.

SOURCE...Radar indicated.

IMPACT...Life threatening flash flooding of creeks and streams,
         roads, and low lying areas.

Some locations that will experience flash flooding include...
  Eastern Denver, northwestern Aurora, and Buckley SFB.

This includes the following streams and drainages...
  Toll Gate Creek, Sand Creek, Cherry Creek, South Platte River,
  First Creek, East Toll Gate Creek, West Toll Gate Creek, Murphy
  Creek, Coal Creek, Westerly Creek, Third Creek and Second Creek.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around, don't drown when encountering flooded roads. Most flood
deaths occur in vehicles.

Move to higher ground now. Act quickly to protect your life.

Excessive runoff from this storm will cause flash flooding of small
creeks and streams, highways, streets, underpasses, drainage areas
and other low lying spots.

&&

LAT...LON 3963 10489 3974 10493 3980 10480 3980 10479
      3981 10479 3981 10476 3982 10476 3982 10468
      3967 10474 3964 10480
PARTITION...408005

FLASH FLOOD...RADAR INDICATED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE
EXPECTED RAINFALL RATE...1.5-3 INCHES IN 45 MINUTES

$$

20

979 
WGUS75 KBOU 152136
FFSBOU

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

COC001-005-031-152345-
/O.CON.KBOU.FF.W.0030.000000T0000Z-260815T2345Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Adams CO-Arapahoe CO-Denver CO-
336 PM MDT Sat Aug 15 2026

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 545 PM MDT THIS
AFTERNOON FOR WESTERN ADAMS, WESTERN ARAPAHOE, AND EASTERN DENVER
COUNTIES...

At 336 PM MDT, Broadcast media reported flash flooding was occurring
near Chambers and Iliff, and Mississippi and Havana. Between 1.5 and
3 inches of rain have fallen. Additional rainfall amounts up to 0.2
inches are possible in the warned area. Flash flooding is already
occurring.

HAZARD...Life threatening flash flooding. Heavy rain producing flash
         flooding.

SOURCE...Broadcast media reported.

IMPACT...Life threatening flash flooding of creeks and streams,
         roads, and low lying areas.

Some locations that will experience flash flooding include...
  Eastern Denver, Aurora, and Buckley SFB.

This includes the following streams and drainages...
  Toll Gate Creek, Sand Creek, Cherry Creek, South Platte River,
  First Creek, East Toll Gate Creek, West Toll Gate Creek, Murphy
  Creek, Coal Creek, Westerly Creek, Third Creek and Second Creek.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around, don't drown when encountering flooded roads. Most flood
deaths occur in vehicles.

Move to higher ground now. Act quickly to protect your life.

Excessive runoff from this storm will cause flash flooding of small
creeks and streams, highways, streets, underpasses, drainage areas
and other low lying spots.

&&

LAT...LON 3963 10489 3974 10493 3980 10480 3980 10479
      3981 10479 3981 10476 3982 10476 3982 10468
      3967 10474 3964 10480
PARTITION...408005

FLASH FLOOD...OBSERVED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE

$$

20

115 
WGUS75 KBOU 152337
FFSBOU

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

COC001-005-031-152347-
/O.EXP.KBOU.FF.W.0030.000000T0000Z-260815T2345Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Adams CO-Arapahoe CO-Denver CO-
537 PM MDT Sat Aug 15 2026

...FLASH FLOOD WARNING WILL EXPIRE AT 545 PM MDT THIS AFTERNOON FOR
SOUTHWESTERN ADAMS, NORTHWESTERN ARAPAHOE, AND EASTERN DENVER
COUNTIES...

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

A Flood Watch remains in effect until 1000 PM MDT for portions of
central, east central, north central, and northeast Colorado.

&&

LAT...LON 3963 10489 3974 10493 3980 10480 3980 10479
      3981 10479 3981 10476 3982 10476 3982 10468
      3967 10474 3964 10480
PARTITION...408005

$$

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
116 PM MDT Sat Aug 15 2026

COZ036-039-151945-
Boulder And Jefferson Counties Below 6000 Feet/West Broomfield
County CO-Jefferson and West Douglas Counties Above
6000 Feet/Gilpin/Clear Creek/Northeast Park Counties Below
9000 Feet CO-
116 PM MDT Sat Aug 15 2026

...A STRONG THUNDERSTORM WILL IMPACT CENTRAL JEFFERSON AND
NORTHWESTERN DOUGLAS COUNTIES UNTIL 145 PM MDT...

At 116 PM MDT, Doppler radar was tracking a strong thunderstorm over
Indian Hills, or 18 miles southwest of Denver, moving east at 15 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...
  Lakewood, southern Golden, Evergreen, Morrison, Tiny Town, Red
  Rocks Park, Indian Hills, Idledale, Kittredge, Aspen Park,
  Chatfield Reservoir, Ken Caryl, Pleasant View, Genesee and
  Columbine.

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 3950 10530 3969 10533 3976 10508 3967 10506
      3967 10508 3965 10506 3964 10508 3963 10511
      3962 10509 3963 10508 3962 10507 3961 10510
      3961 10506 3962 10505 3957 10505 3954 10507
      3950 10509
TIME...MOT...LOC 1915Z 261DEG 11KT 3960 10526

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

63

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.

&&