Alert archive / Colorado / Flash Flood Warnings in 2021

Flash Flood Warning 39, NWS Denver/Boulder, CO

July 23, 2021Clear Creek County, Gilpin County, Colorado

NWS Denver/Boulder, CO issued this flash flood warning at Jul 23, 2021, 4:51 PM MDT for Clear Creek County, Gilpin County, Colorado. It was in force for 114 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued: Jul 23, 2021, 4:51 PM MDT (22:51 UTC)
Expired: Jul 23, 2021, 6:45 PM MDT
In force: 114 min
Issued by: NWS Denver/Boulder, CO
Area: Storm-based polygon
Flood severity: None

Counties Clear Creek County, CO, Gilpin County, CO

The radar

The Denver radar (KFTG), 81 km from the middle of the area, began a volume at 22:51 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.

The nearest sounding before it

Denver, CO (KDNR), launched 12:00Z, 10.9 hours before the alert went out and 194 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: 36 J/kg
Mixed-layer CIN: -253 J/kg
Mixed-layer LCL: 2235 m above ground
0-6 km bulk shear: 11 kt
0-1 km storm-relative helicity: -31 m²/s²
0-3 km storm-relative helicity: 15 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

295 
WGUS55 KBOU 232251
FFWBOU
COC019-047-240045-
/O.NEW.KBOU.FF.W.0039.210723T2251Z-210724T0045Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Denver CO
451 PM MDT Fri Jul 23 2021

The National Weather Service in Denver has issued a

* Flash Flood Warning for...
  Southeastern Clear Creek County in central Colorado...
  Southeastern Gilpin County in central Colorado...

* Until 645 PM MDT.

* At 451 PM MDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 1.5 and 2.5 inches of 
  rain have fallen. Additional rainfall amounts of 0.5 to 1 inch are 
  possible in the warned area. Flash flooding is ongoing or expected 
  to begin shortly.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Radar.

  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...
  I-70 near Idaho Springs, Central City, Black Hawk, Blue Valley, 
  Echo Lake, Brookvale and Russell Gulch.

The heaviest rain has fallen across the Corral Creek drainage in 
southeast Clear Creek County.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3979 10555 3983 10551 3983 10545 3976 10544
      3974 10544 3971 10540 3966 10540 3961 10540
      3960 10540 3962 10565 3971 10565

FLASH FLOOD...RADAR INDICATED

$$

Schlatter

1 follow-up statement

282 
WGUS75 KBOU 240037
FFSBOU

Flash Flood Statement
National Weather Service Denver CO
637 PM MDT Fri Jul 23 2021

COC019-047-240047-
/O.EXP.KBOU.FF.W.0039.000000T0000Z-210724T0045Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Clear Creek CO-Gilpin CO-
637 PM MDT Fri Jul 23 2021

...FLASH FLOOD WARNING WILL EXPIRE AT 645 PM MDT THIS EVENING FOR 
SOUTHEASTERN CLEAR CREEK AND SOUTHEASTERN GILPIN COUNTIES...

The heavy rain has ended. Flooding is no longer expected to pose a 
threat and so far the National Weather Service in Boulder has not 
received any reports of flooding in Clear Creek County.

LAT...LON 3979 10555 3983 10551 3983 10545 3976 10544
      3974 10544 3971 10540 3966 10540 3961 10540
      3960 10540 3962 10565 3971 10565

$$

Schlatter

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 22, 6:51 PM MDT	Areal Flood Advisory	BOU	Adams, Denver, Jefferson	84 min
Jul 22, 7:10 PM MDT	Areal Flood Advisory	BOU	Douglas	95 min
Jul 23, 2:30 PM MDT	Special Weather Statement	BOU	Boulder	30 min
Jul 23, 2:41 PM MDT	Areal Flood Advisory	BOU	Grand	84 min
Jul 23, 2:50 PM MDT	Special Weather Statement	BOU	Summit	25 min
Jul 23, 4:05 PM MDT	Flash Flood Warning Considerable damage threat	BOU	Grand	3 hr
Jul 23, 4:11 PM MDT	Areal Flood Advisory	BOU	Clear Creek	2 hr

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; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.