Alert archive / Colorado / Flash Flood Warnings in 2021

Flash Flood Warning 23, NWS Denver/Boulder, CO

July 5, 2021Grand County, Colorado

NWS Denver/Boulder, CO issued this flash flood warning at Jul 5, 2021, 3:28 PM MDT for Grand County, Colorado. It was in force for 92 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 5, 2021, 3:28 PM MDT (21:28 UTC)
Expired: Jul 5, 2021, 5:00 PM MDT
In force: 92 min
Issued by: NWS Denver/Boulder, CO
Area: Storm-based polygon
Flood severity: None

County Grand County, CO

The radar

The Cheyenne radar (KCYS), 146 km from the middle of the area, began a volume at 21:32 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

Grand Junction, CO (KGJT), launched 12:00Z, 9.5 hours before the alert went out and 241 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: 5 J/kg
Mixed-layer CIN: -276 J/kg
Mixed-layer LCL: 3199 m above ground
0-6 km bulk shear: 10 kt
0-1 km storm-relative helicity: -13 m²/s²
0-3 km storm-relative helicity: 26 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

262 
WGUS55 KBOU 052128
FFWBOU
COC049-052300-
/O.NEW.KBOU.FF.W.0023.210705T2128Z-210705T2300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Denver CO
328 PM MDT Mon Jul 5 2021

The National Weather Service in Denver has issued a

* Flash Flood Warning for...
  North Central Grand County in north central Colorado...

* Until 500 PM MDT.

* At 328 PM MDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 0.75 and 1.25 inches of 
  rain have fallen. 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...
  mainly rural areas of North Central Grand County

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Heavy Rainfall will cause flash flooding of small creeks, streams, 
and ditches in the northwest portion of the East Troublesome burn 
area. Rock slides or debris flows can also be expected across rural 
roads.

&&

LAT...LON 4035 10611 4035 10604 4023 10607 4024 10622
      4033 10621 4033 10619 4034 10618 4034 10617
      4034 10616 4033 10615 4033 10614 4034 10613

FLASH FLOOD...RADAR INDICATED

$$

RPK

2 follow-up statements

736 
WGUS75 KBOU 052207
FFSBOU

Flash Flood Statement
National Weather Service Denver CO
407 PM MDT Mon Jul 5 2021

COC049-052300-
/O.CON.KBOU.FF.W.0023.000000T0000Z-210705T2300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Grand CO-
407 PM MDT Mon Jul 5 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 5 PM MDT THIS 
AFTERNOON FOR NORTH CENTRAL GRAND COUNTY...

At 407 PM MDT, Doppler radar indicated thunderstorms producing heavy 
rain across the warned area. Between 0.75 and 1.25 inches of rain 
have fallen. 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...
  mainly rural areas of North Central Grand County

This includes the following streams and drainages...
  Buffalo Creek, East Fork Troublesome Creek, Middle Fork Creek, 
  Ethel Creek, Illinois River, East Branch Willow Creek, Willow 
  Creek, Trail Creek and Trout Creek.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Heavy Rainfall will cause flash flooding of small creeks, streams, 
and ditches in the northwest portion of the East Troublesome burn 
area. Rock slides or debris flows can also be expected across rural 
roads.

&&

LAT...LON 4035 10611 4035 10604 4023 10607 4024 10622
      4033 10621 4033 10619 4034 10618 4034 10617
      4034 10616 4033 10615 4033 10614 4034 10613

FLASH FLOOD...RADAR INDICATED

$$

RPK

268 
WGUS75 KBOU 052255
FFSBOU

Flash Flood Statement
National Weather Service Denver CO
455 PM MDT Mon Jul 5 2021

COC049-052305-
/O.EXP.KBOU.FF.W.0023.000000T0000Z-210705T2300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Grand CO-
455 PM MDT Mon Jul 5 2021

...FLASH FLOOD WARNING WILL EXPIRE AT 5 PM MDT THIS AFTERNOON FOR 
NORTH CENTRAL GRAND COUNTY...

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

A Flash Flood Watch remains in effect until 1200 AM MDT Tuesday for 
Portions of central and north central Colorado.

LAT...LON 4035 10611 4035 10604 4023 10607 4024 10622
      4033 10621 4033 10619 4034 10618 4034 10617
      4034 10616 4033 10615 4033 10614 4034 10613

$$

RPK

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 5, 3:13 AM MDT	Flash Flood Watch	BOU	Boulder, Grand, Jackson, Larimer, Summit	21 hr
Jul 5, 1:29 PM MDT	Areal Flood Advisory	BOU	Park	91 min
Jul 5, 1:36 PM MDT	Areal Flood Advisory	BOU	Grand	84 min
Jul 5, 1:39 PM MDT	Flash Flood Warning	BOU	Larimer	96 min
Jul 5, 1:53 PM MDT	Areal Flood Advisory	BOU	Larimer	82 min
Jul 5, 2:00 PM MDT	Flash Flood Warning	BOU	Grand	90 min
Jul 5, 2:12 PM MDT	Flash Flood Warning	BOU	Larimer	93 min
Jul 5, 2:22 PM MDT	Special Weather Statement	BOU	Teller	23 min
Jul 5, 2:23 PM MDT	Areal Flood Advisory	BOU	Park	97 min
Jul 5, 2:44 PM MDT	Special Weather Statement	BOU	Clear Creek	31 min
Jul 5, 4:18 PM MDT	Areal Flood Advisory	BOU	Clear Creek, Park	87 min
Jul 5, 5:14 PM MDT	Areal Flood Advisory	BOU	Arapahoe, Douglas	91 min
Jul 5, 5:31 PM MDT	Flash Flood Warning	BOU	Grand	89 min
Jul 5, 5:51 PM MDT	Special Weather Statement	BOU	Denver	24 min
Jul 5, 5:53 PM MDT	Areal Flood Advisory	BOU	Arapahoe	97 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; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.