Alert archive / Colorado / Flash Flood Warnings in 2021

Flash Flood Warning 20, NWS Denver/Boulder, CO

July 5, 2021Larimer County, Colorado

NWS Denver/Boulder, CO issued this flash flood warning at Jul 5, 2021, 1:39 PM MDT for Larimer County, Colorado. It was in force for 96 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, 1:39 PM MDT (19:39 UTC)
Expired: Jul 5, 2021, 3:15 PM MDT
In force: 96 min
Issued by: NWS Denver/Boulder, CO
Area: Storm-based polygon
Flood severity: None

County Larimer County, CO

The radar

The Cheyenne radar (KCYS), 95 km from the middle of the area, began a volume at 19:39 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, 7.7 hours before the alert went out and 236 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: 1 J/kg
Mixed-layer CIN: -470 J/kg
Mixed-layer LCL: 2151 m above ground
0-6 km bulk shear: 20 kt
0-1 km storm-relative helicity: -8 m²/s²
0-3 km storm-relative helicity: 65 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

332 
WGUS55 KBOU 051939
FFWBOU
COC069-052115-
/O.NEW.KBOU.FF.W.0020.210705T1939Z-210705T2115Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

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

The National Weather Service in Denver has issued a

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

* Until 315 PM MDT.

* At 139 PM MDT, Doppler radar indicated thunderstorms producing 
  heavy rain across 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...
  Kinikinik.

This includes the following additional locations...
	The Upper Poudre Canyon.

This includes the following streams and drainages...
  Peterson Creek, Sheep Creek, Cache La Poudre River, Laramie River, 
  Elkhorn Creek, Brinker Creek, Roaring Creek and South Lone Pine 
  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 affected part of the Cameron Peak burn area. Rock 
slides or debris flows can also be expected across rural roads.

&&

LAT...LON 4076 10584 4076 10568 4065 10570 4065 10586

FLASH FLOOD...RADAR INDICATED

$$

RPK

3 follow-up statements

969 
WGUS75 KBOU 052006
FFSBOU

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

COC069-052115-
/O.CON.KBOU.FF.W.0020.000000T0000Z-210705T2115Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Larimer CO-
206 PM MDT Mon Jul 5 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 315 PM MDT THIS 
AFTERNOON FOR CENTRAL LARIMER COUNTY...

At 206 PM MDT, Doppler radar indicated thunderstorms producing heavy 
rain across the warned area. 0.75 to 1.25 inches of rain has fallen. 
Flash flooding is ongoing or expected to begin shortly.

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

SOURCE...Radar.

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

Some locations that will experience flash flooding include...
  Kinikinik.

This includes the following additional locations...
	The Upper Poudre Canyon.

This includes the following streams and drainages...
  Peterson Creek, Sheep Creek, Cache La Poudre River, Laramie River, 
  Elkhorn Creek, Brinker Creek, Roaring Creek and South Lone Pine 
  Creek.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

THIS IS A LIFE THREATENING SITUATION! Heavy Rainfall will cause 
extensive and severe flooding of creeks, streams, roads and culverts 
in the affected part of the Cameron Peak burn area. Rock slides or 
debris flows can also be expected across roads in the warning area.

&&

LAT...LON 4076 10584 4076 10568 4065 10570 4065 10586

FLASH FLOOD...RADAR INDICATED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE

$$

RPK

579 
WGUS75 KBOU 052038
FFSBOU

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

COC069-052115-
/O.CON.KBOU.FF.W.0020.000000T0000Z-210705T2115Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Larimer CO-
238 PM MDT Mon Jul 5 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 315 PM MDT THIS 
AFTERNOON FOR CENTRAL LARIMER COUNTY...

At 238 PM MDT, Doppler radar indicated thunderstorms producing heavy 
rain across the warned area. Between 1 and 1.5 inches of rain have 
fallen. Flash flooding is ongoing or expected to begin shortly.

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

SOURCE...Radar.

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

Some locations that will experience flash flooding include...
  Kinikinik.

This includes the following additional locations...
	The Upper Poudre Canyon.

This includes the following streams and drainages...
  Peterson Creek, Sheep Creek, Cache La Poudre River, Laramie River, 
  Elkhorn Creek, Brinker Creek, Roaring Creek and South Lone Pine 
  Creek.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

THIS IS A LIFE THREATENING SITUATION! Heavy Rainfall will cause 
extensive and severe flooding of creeks, streams, roads and culverts 
in the affected part of the Cameron Peak burn area. Rock slides or 
debris flows can also be expected across roads in the warning area.

&&

LAT...LON 4076 10584 4076 10568 4065 10570 4065 10586

FLASH FLOOD...RADAR INDICATED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE

$$

RPK

239 
WGUS75 KBOU 052113
FFSBOU

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

COC069-052123-
/O.EXP.KBOU.FF.W.0020.000000T0000Z-210705T2115Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Larimer CO-
313 PM MDT Mon Jul 5 2021

...FLASH FLOOD WARNING WILL EXPIRE AT 315 PM MDT THIS AFTERNOON FOR 
CENTRAL LARIMER COUNTY...

The heavy rain has ended. Flooding is no longer expected to pose a 
threat in the short term. However, additional storms may move across 
in the next hour with additional heavy rainfall.

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

LAT...LON 4076 10584 4076 10568 4065 10570 4065 10586

$$

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, 1:53 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, 3:28 PM MDT	Flash Flood Warning	BOU	Grand	92 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.