Alert archive / Colorado / Flash Flood Warnings in 2021

Flash Flood Warning 22, NWS Denver/Boulder, CO

July 5, 2021Larimer County, Colorado

NWS Denver/Boulder, CO issued this flash flood warning at Jul 5, 2021, 2:12 PM MDT for Larimer County, Colorado. It was in force for 93 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, 2:12 PM MDT (20:12 UTC)
Expired
Jul 5, 2021, 3:45 PM MDT
In force
93 min
Issued by
NWS Denver/Boulder, CO
Area
Storm-based polygon
Flood severity
None

County Larimer County, CO

The radar

The Cheyenne radar (KCYS), 103 km from the middle of the area, began a volume at 20:14 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, 8.2 hours before the alert went out and 230 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-pSkew-T log-p diagram, Denver, CO at 12:00Z on 2021-07-05Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Denver, CO at 12:00Z on 2021-07-05The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -8 square meters per square second.193958Sfc1 km3 km6 km9 kmRMLM
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.

842 
WGUS55 KBOU 052012
FFWBOU
COC069-052145-
/O.NEW.KBOU.FF.W.0022.210705T2012Z-210705T2145Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Denver CO
212 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 345 PM MDT.

* At 212 PM MDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 0.75 and 1.0 inch 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 Central Larimer County

This includes the following additional locations...
The Upper Poudre Canyon, Remote areas in the Cameron Peak Wilderness 
and Hague Creek.

This includes the following streams and drainages...
  Joe Wright Creek, Cache La Poudre River, Laramie River, Poudre 
  Pass Creek, La, Mummy Pass Creek and Fall 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 4065 10585 4065 10570 4057 10566 4048 10573
      4051 10583

FLASH FLOOD...RADAR INDICATED

$$

RPK
2 follow-up statements
140 
WGUS75 KBOU 052041
FFSBOU

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

COC069-052145-
/O.CON.KBOU.FF.W.0022.000000T0000Z-210705T2145Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Larimer CO-
241 PM MDT Mon Jul 5 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 345 PM MDT THIS 
AFTERNOON FOR CENTRAL LARIMER COUNTY...

At 241 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 Central Larimer County

This includes the following additional locations...
The Upper Poudre Canyon, Remote areas in the Cameron Peak Wilderness 
and Hague Creek.

This includes the following streams and drainages...
  Joe Wright Creek, Cache La Poudre River, Laramie River, Poudre 
  Pass Creek, La, Mummy Pass Creek and Fall 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 4065 10585 4065 10570 4057 10566 4048 10573
      4051 10583

FLASH FLOOD...RADAR INDICATED

$$

RPK
071 
WGUS75 KBOU 052141
FFSBOU

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

COC069-052151-
/O.EXP.KBOU.FF.W.0022.000000T0000Z-210705T2145Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Larimer CO-
341 PM MDT Mon Jul 5 2021

...FLASH FLOOD WARNING WILL EXPIRE AT 345 PM MDT THIS AFTERNOON FOR 
CENTRAL LARIMER 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 4065 10585 4065 10570 4057 10566 4048 10573
      4051 10583

$$

RPK

The office that day

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

IssuedProductOfficeCountiesLasted
Jul 5, 3:13 AM MDTFlash Flood WatchBOUBoulder, Grand, Jackson, Larimer, Summit21 hr
Jul 5, 1:29 PM MDTAreal Flood AdvisoryBOUPark91 min
Jul 5, 1:36 PM MDTAreal Flood AdvisoryBOUGrand84 min
Jul 5, 1:39 PM MDTFlash Flood WarningBOULarimer96 min
Jul 5, 1:53 PM MDTAreal Flood AdvisoryBOULarimer82 min
Jul 5, 2:00 PM MDTFlash Flood WarningBOUGrand90 min
Jul 5, 2:22 PM MDTSpecial Weather StatementBOUTeller23 min
Jul 5, 2:23 PM MDTAreal Flood AdvisoryBOUPark97 min
Jul 5, 2:44 PM MDTSpecial Weather StatementBOUClear Creek31 min
Jul 5, 3:28 PM MDTFlash Flood WarningBOUGrand92 min
Jul 5, 4:18 PM MDTAreal Flood AdvisoryBOUClear Creek, Park87 min
Jul 5, 5:14 PM MDTAreal Flood AdvisoryBOUArapahoe, Douglas91 min
Jul 5, 5:31 PM MDTFlash Flood WarningBOUGrand89 min
Jul 5, 5:51 PM MDTSpecial Weather StatementBOUDenver24 min
Jul 5, 5:53 PM MDTAreal Flood AdvisoryBOUArapahoe97 min

Nearby

Flash Flood Warnings in Colorado, 2021Every 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.