Alert archive / Colorado / Flash Flood Warnings in 2021

Flash Flood Warning 79, NWS Denver/Boulder, CO

August 19, 2021Phillips County, Colorado

NWS Denver/Boulder, CO issued this flash flood warning at Aug 19, 2021, 10:38 PM MDT for Phillips County, Colorado. It was in force for 4 hr. 2 reports 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: Aug 19, 2021, 10:38 PM MDT (04:38 UTC)
Expired: Aug 20, 2021, 3:00 AM MDT
In force: 4 hr
Issued by: NWS Denver/Boulder, CO
Area: Storm-based polygon
Damage threat: Considerable
Flood severity: None

County Phillips County, CO

The radar

The Goodland radar (KGLD), 136 km from the middle of the area, began a volume at 04:39 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.

What was reported inside it

Time	Report	Where	Remark
Aug 19, 11:00 PM MDT	HEAVY RAIN 7.7	Holyoke, CO
Aug 19, 11:45 PM MDT	FLASH FLOOD	8 S Pleasant Valley, CO	UP TO 9 INCHES OF RAIN WITH SUBSTANTIAL FLASH FLOODING.

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 00:00Z, 4.6 hours before the alert went out and 113 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: 56 J/kg
Mixed-layer CIN: -210 J/kg
Mixed-layer LCL: 1497 m above ground
0-6 km bulk shear: 52 kt
0-1 km storm-relative helicity: 52 m²/s²
0-3 km storm-relative helicity: 222 m²/s²
Significant tornado parameter: 0.0
Supercell composite: -0.0

Open this sounding in Storm Lab

The text

As transmitted.

093 
WGUS55 KBOU 200438
FFWBOU
COC095-200900-
/O.NEW.KBOU.FF.W.0079.210820T0438Z-210820T0900Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Denver CO
1038 PM MDT Thu Aug 19 2021

The National Weather Service in Denver has issued a

* Flash Flood Warning for...
  Eastern Phillips County in northeastern Colorado...

* Until 300 AM MDT.

* At 1038 PM MDT, Local law enforcement reported several roads are 
  being flooded across eastern Phillips county, including Highway 6 
  east of Holyoke. Between 4 and 8 inches of rain have fallen. 
  Additional rainfall amounts up to 2 inches are possible in the 
  warned area. Life threatening flash flooding is already occurring.

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

  SOURCE...Law enforcement reported.

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

* Some locations that will experience flash flooding include...
  Holyoke, Amherst and Pleasant Valley.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Avoid driving tonight due to many roads being flooded. Some roads 
may wash out. It is very difficult to recognize these dangers of 
flooding at night.

If you live in a low lying area or a flood prone area, you need to 
monitor water levels tonight and seek higher ground if flooding is 
imminent.



&&

LAT...LON 4044 10249 4053 10244 4060 10240 4062 10237
      4069 10227 4075 10205 4070 10205 4063 10205
      4055 10205 4054 10205 4050 10205 4049 10205
      4047 10205 4044 10205 4044 10209 4044 10218
      4044 10222 4044 10225 4044 10234 4044 10242

FLASH FLOOD...OBSERVED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE

$$

Meier

1 follow-up statement

419 
WGUS75 KBOU 200644
FFSBOU

Flash Flood Statement
National Weather Service Denver CO
1244 AM MDT Fri Aug 20 2021

COC095-200900-
/O.CON.KBOU.FF.W.0079.000000T0000Z-210820T0900Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Phillips CO-
1244 AM MDT Fri Aug 20 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 3 AM MDT EARLY THIS 
MORNING FOR EASTERN PHILLIPS COUNTY...

At 1244 AM MDT, Local law enforcement reported several roads are 
being flooded across eastern Phillips county, including Highway 6 
east of Holyoke. Between 4 and 9 inches of rain have fallen. Life 
threatening flash flooding is already occurring.

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

SOURCE...Law enforcement reported.

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

Some locations that will experience flash flooding include...
  Holyoke, Amherst and Pleasant Valley.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Avoid driving tonight due to many roads being flooded. Some roads 
may wash out. It is very difficult to recognize these dangers of 
flooding at night.

If you live in a low lying area or a flood prone area, you need to 
monitor water levels tonight and seek higher ground if flooding is 
imminent.



&&

LAT...LON 4044 10249 4053 10244 4060 10240 4062 10237
      4069 10227 4075 10205 4070 10205 4063 10205
      4055 10205 4054 10205 4050 10205 4049 10205
      4047 10205 4044 10205 4044 10209 4044 10218
      4044 10222 4044 10225 4044 10234 4044 10242

FLASH FLOOD...OBSERVED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE

$$

Meier

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 19, 6:21 PM MDT	Severe Thunderstorm Warning	BOU	Phillips	24 min
Aug 19, 6:41 PM MDT	Severe Thunderstorm Warning Considerable damage threat	BOU	Phillips	49 min
Aug 19, 6:43 PM MDT	Areal Flood Advisory	BOU	Phillips	2 hr
Aug 19, 7:43 PM MDT	Flash Flood Warning Considerable damage threat	BOU	Phillips	3 hr
Aug 20, 2:12 AM MDT	Areal Flood Advisory	BOU	Larimer	93 min
Aug 20, 2:15 AM MDT	Flash Flood Warning	BOU	Larimer	2 hr
Aug 20, 2:58 AM MDT	Areal Flood Warning	BOU	Phillips	9 hr
Aug 20, 4:01 AM MDT	Special Weather Statement	BOU	Morgan	44 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.