Alert archive / Colorado / Flash Flood Warnings in 2021

Flash Flood Warning 43, NWS Denver/Boulder, CO

July 30, 2021Larimer County, Colorado

NWS Denver/Boulder, CO issued this flash flood warning at Jul 30, 2021, 1:14 PM MDT for Larimer County, Colorado. It was in force for 3 hr. 1 report 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, 1:14 PM MDT (19:14 UTC)
Expired
Jul 30, 2021, 4:15 PM MDT
In force
3 hr
Issued by
NWS Denver/Boulder, CO
Area
Storm-based polygon
Damage threat
Considerable
Flood severity
None

County Larimer County, CO

The radar

The Cheyenne radar (KCYS), 94 km from the middle of the area, began a volume at 19:14 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.

What was reported inside it

TimeReportWhereRemark
Jul 30, 1:52 PM MDTFLASH FLOOD2 Sw Kinikinik, COWATER OVER ROUTE 14 NEAR MM 80.

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 12:00Z, 7.2 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-pSkew-T log-p diagram, Denver, CO at 12:00Z on 2021-07-30Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 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 2021-07-30The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -18 square meters per square second.1939Sfc1 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
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
2523 m above ground
0-6 km bulk shear
18 kt
0-1 km storm-relative helicity
-18 m²/s²
0-3 km storm-relative helicity
2 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

908 
WGUS55 KBOU 301914
FFWBOU
COC069-302215-
/O.NEW.KBOU.FF.W.0043.210730T1914Z-210730T2215Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

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

The National Weather Service in Denver has issued a

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

* Until 415 PM MDT.

* At 114 PM MDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 0.5 and 1 inch of rain 
  has 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...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.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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 4074 10583 4077 10584 4080 10578 4079 10569
      4075 10572 4068 10572 4063 10575 4064 10583

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

$$

Bowen
1 follow-up statement
048 
WGUS75 KBOU 302038
FFSBOU

Flash Flood Statement
National Weather Service Denver CO
238 PM MDT Fri Jul 30 2021

COC069-302215-
/O.CON.KBOU.FF.W.0043.000000T0000Z-210730T2215Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Larimer CO-
238 PM MDT Fri Jul 30 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 415 PM MDT THIS 
AFTERNOON FOR CENTRAL LARIMER COUNTY...

At 238 PM MDT, Doppler radar indicated nearly stationary 
thunderstorms continuing to produce heavy rain across the warned 
area. Between 0.5 and 1 inch of rain has 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...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.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Heed any road closures and DO NOT DRIVE INTO FLOODED AREAS. If you 
are in a flooded area, abandon your vehicle and climb to safety.

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 4074 10583 4077 10584 4080 10578 4079 10569
      4075 10572 4068 10572 4063 10575 4064 10583

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

$$

TH

The office that day

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

IssuedProductOfficeCountiesLasted
Jul 29, 6:37 PM MDTAreal Flood AdvisoryBOUGrand83 min
Jul 29, 7:27 PM MDTAreal Flood AdvisoryBOUGrand93 min
Jul 29, 7:50 PM MDTFlash Flood WarningBOUJackson, Larimer3 hr
Jul 29, 8:14 PM MDTFlash Flood WarningBOUGrand112 min
Jul 29, 9:32 PM MDTSpecial Weather StatementBOUJackson28 min
Jul 29, 10:19 PM MDTAreal Flood AdvisoryBOULarimer86 min
Jul 30, 1:01 PM MDTFlash Flood WarningBOULarimer7 hr
Jul 30, 1:08 PM MDTAreal Flood AdvisoryBOULarimer6 min
Jul 30, 1:34 PM MDTFlash Flood Warning Considerable damage threatBOULarimer6 hr
Jul 30, 2:07 PM MDTFlash Flood WarningBOULarimer5 hr
Jul 30, 2:30 PM MDTFlash Flood WarningBOUClear Creek, Grand3 hr
Jul 30, 2:48 PM MDTAreal Flood AdvisoryBOULarimer87 min
Jul 30, 2:51 PM MDTFlash Flood WarningBOUGrand4 hr
Jul 30, 3:02 PM MDTFlash Flood WarningBOUGrand3 hr
Jul 30, 3:02 PM MDTSpecial Weather StatementBOULarimer43 min
Jul 30, 3:26 PM MDTSevere Thunderstorm WarningBOULarimer, Weld49 min
Jul 30, 3:45 PM MDTAreal Flood AdvisoryBOUGrand2 hr
Jul 30, 3:59 PM MDTAreal Flood AdvisoryBOULarimer, Weld61 min
Jul 30, 4:11 PM MDTSevere Thunderstorm WarningBOULarimer, Weld49 min
Jul 30, 4:16 PM MDTFlash Flood WarningBOUGrand3 hr
Jul 30, 4:28 PM MDTFlash Flood WarningBOUPark3 hr
Jul 30, 4:30 PM MDTFlash Flood WarningBOULarimer4 hr
Jul 30, 5:36 PM MDTFlash Flood Warning EmergencyCatastrophic damage threatBOULarimer3 hr
Jul 30, 5:37 PM MDTFlash Flood WarningBOUGrand99 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.