Alert archive / Colorado / Flash Flood Warnings in 2021

Flash Flood Warning 54, NWS Denver/Boulder, CO

July 30, 2021Boulder County, Broomfield County, Weld County, Colorado

NWS Denver/Boulder, CO issued this flash flood warning at Jul 30, 2021, 10:18 PM MDT for Boulder County, Broomfield County, Weld County, Colorado. It was in force for 3 hr. 2 reports came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued: Jul 30, 2021, 10:18 PM MDT (04:18 UTC)
Expired: Jul 31, 2021, 1:30 AM MDT
In force: 3 hr
Issued by: NWS Denver/Boulder, CO
Area: Storm-based polygon
Flood severity: None

Counties Boulder County, CO, Broomfield County, CO, Weld County, CO

The radar

The Denver radar (KFTG), 47 km from the middle of the area, began a volume at 04:21 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

What was reported inside it

Time	Report	Where	Remark
Jul 30, 10:30 PM MDT	FLASH FLOOD	2 Se Erie, CO	SOCIAL MEDIA POST. CAR STUCK IN FLOODED INTERSECTION OF MOUNTAIN VIEW BLVD AND RIDGEVIEW DRIVE. RAIN GAGES INDICATE 3.5 TO 4.5 INCHES OF RAIN HAD FALLEN JUST NORTHWEST OF THE AREA.
Jul 30, 10:45 PM MDT	FLASH FLOOD	2 Se Erie, CO	RESCUE OF PERSONS IN A CAR WHICH WAS CAUGHT IN FLOODWATERS AT THE INTERSECTION OF HWY 7 & MOUNTAIN VIEW BLVD. THERE WERE ALSO A COUPLE OF FLOODED BASEMENTS IN THE AREA.

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The nearest sounding before it

Denver, CO (KDNR), launched 00:00Z, 4.3 hours before the alert went out and 150 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 553 J/kg
Mixed-layer CIN: -21 J/kg
Mixed-layer LCL: 2602 m above ground
0-6 km bulk shear: 24 kt
0-1 km storm-relative helicity: 18 m²/s²
0-3 km storm-relative helicity: 49 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.6

Open this sounding in Storm Lab

The text

As transmitted.

267 
WGUS55 KBOU 310418
FFWBOU
COC013-014-123-310730-
/O.NEW.KBOU.FF.W.0054.210731T0418Z-210731T0730Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Denver CO
1018 PM MDT Fri Jul 30 2021

The National Weather Service in Denver has issued a

* Flash Flood Warning for...
  East Central Boulder County in northeastern Colorado...
  Northeastern Broomfield County in northeastern Colorado...
  Southwestern Weld County in northeastern Colorado...

* Until 130 AM MDT.

* At 1018 PM MDT, Doppler radar and automated rain gauges indicated 
  thunderstorms producing heavy rain across the warned area. Between 
  3 and 5 inches of rain have fallen. Additional rainfall amounts of 
  1 to 2 inches are possible in the warned area. Flash flooding is 
  ongoing or expected to begin shortly.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Radar and automated gauges.

  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...
  Northern Thornton, northeastern Broomfield, Lafayette, Erie, 
  Firestone, Frederick, Dacono, Mead and Platteville.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Be especially cautious at night when it is harder to recognize the 
dangers of flooding.

&&

LAT...LON 3998 10510 4003 10510 4009 10507 4020 10497
      4026 10486 4025 10480 4021 10478 4013 10484
      4002 10491 4000 10494 4000 10498 3998 10499
      3998 10500 3998 10502 3996 10502 3995 10504

FLASH FLOOD...RADAR AND GAUGE INDICATED

$$

Danielson

1 follow-up statement

900 
WGUS75 KBOU 310722
FFSBOU

Flash Flood Statement
National Weather Service Denver CO
122 AM MDT Sat Jul 31 2021

COC013-014-123-310732-
/O.EXP.KBOU.FF.W.0054.000000T0000Z-210731T0730Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Boulder CO-Broomfield CO-Weld CO-
122 AM MDT Sat Jul 31 2021

...FLASH FLOOD WARNING WILL EXPIRE AT 130 AM MDT EARLY THIS MORNING 
FOR EAST CENTRAL BOULDER, NORTHEASTERN BROOMFIELD AND SOUTHWESTERN 
WELD COUNTIES...

The heavy rain has ended although light rain is still falling. 
Flooding is no longer expected to pose a threat. Please continue to 
heed remaining road closures.

A Flash Flood Watch remains in effect until 900 PM MDT Saturday for 
Portions of central, north central, and northeast Colorado.

LAT...LON 3998 10510 4003 10510 4009 10507 4020 10497
      4026 10486 4025 10480 4021 10478 4013 10484
      4002 10491 4000 10494 4000 10498 3998 10499
      3998 10500 3998 10502 3996 10502 3995 10504

$$

Danielson

The office that day

Everything else NWS Denver/Boulder, CO issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 30, 6:01 PM MDT	Areal Flood Advisory	BOU	Boulder, Broomfield, Weld	59 min
Jul 30, 6:08 PM MDT	Areal Flood Advisory	BOU	Adams, Denver	82 min
Jul 30, 6:48 PM MDT	Areal Flood Advisory	BOU	Douglas, Elbert	117 min
Jul 30, 7:13 PM MDT	Areal Flood Warning	BOU	Larimer	3 hr
Jul 30, 7:35 PM MDT	Areal Flood Advisory	BOU	Boulder	70 min
Jul 30, 7:52 PM MDT	Areal Flood Advisory	BOU	Boulder, Broomfield, Weld	83 min
Jul 30, 7:53 PM MDT	Areal Flood Advisory	BOU	Larimer	68 min
Jul 30, 8:19 PM MDT	Areal Flood Advisory	BOU	Douglas, Jefferson	42 min
Jul 30, 9:34 PM MDT	Areal Flood Advisory	BOU	Adams, Boulder, Broomfield, Denver, Jefferson, Weld	56 min
Jul 30, 9:35 PM MDT	Areal Flood Advisory	BOU	Clear Creek, Gilpin	3 hr
Jul 30, 11:17 PM MDT	Special Weather Statement	BOU	Weld	28 min
Jul 30, 11:24 PM MDT	Areal Flood Advisory	BOU	Weld	81 min
Jul 30, 11:40 PM MDT	Areal Flood Advisory	BOU	Weld	60 min
Jul 31, 1:12 AM MDT	Special Weather Statement	BOU	Logan	33 min
Jul 31, 2:39 AM MDT	Special Weather Statement	BOU	Logan	51 min
Jul 31, 3:20 AM MDT	Special Weather Statement	BOU	Phillips, Sedgwick	40 min
Jul 31, 3:59 AM MDT	Areal Flood Advisory	BOU	Logan, Phillips, Sedgwick	74 min
Jul 31, 11:49 AM MDT	Flash Flood Warning	BOU	Larimer	2 hr
Jul 31, 12:27 PM MDT	Flash Flood Warning	BOU	Grand	3 hr
Jul 31, 12:29 PM MDT	Areal Flood Advisory	BOU	Grand	91 min
Jul 31, 12:32 PM MDT	Areal Flood Advisory	BOU	Grand	88 min
Jul 31, 12:34 PM MDT	Areal Flood Advisory	BOU	Grand	86 min
Jul 31, 12:39 PM MDT	Areal Flood Advisory	BOU	Park	81 min
Jul 31, 12:42 PM MDT	Areal Flood Advisory	BOU	Park	93 min
Jul 31, 1:05 PM MDT	Areal Flood Advisory	BOU	Larimer	85 min
Jul 31, 1:33 PM MDT	Areal Flood Advisory	BOU	Grand	87 min
Jul 31, 2:16 PM MDT	Flash Flood Warning	BOU	Larimer	89 min
Jul 31, 2:43 PM MDT	Flash Flood Warning	BOU	Larimer	92 min
Jul 31, 2:57 PM MDT	Areal Flood Advisory	BOU	Park	93 min
Jul 31, 3:24 PM MDT	Flash Flood Warning Considerable damage threat	BOU	Larimer	81 min
Jul 31, 3:29 PM MDT	Areal Flood Advisory	BOU	Boulder	91 min
Jul 31, 3:33 PM MDT	Flash Flood Warning	BOU	Park	3 hr
Jul 31, 3:37 PM MDT	Flash Flood Warning	BOU	Boulder	3 hr
Jul 31, 3:51 PM MDT	Areal Flood Advisory	BOU	Boulder	84 min
Jul 31, 4:31 PM MDT	Areal Flood Advisory	BOU	Park	89 min
Jul 31, 4:42 PM MDT	Areal Flood Advisory	BOU	Park	93 min
Jul 31, 4:52 PM MDT	Areal Flood Advisory	BOU	Park	83 min

Nearby

Flash Flood Warnings in Colorado, 2021 Every flash flood warning in 2021

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.