Alert archive / Colorado / Flash Flood Warnings in 2021

Flash Flood Warning 7, NWS Denver/Boulder, CO

June 30, 2021Weld County, Colorado

NWS Denver/Boulder, CO issued this flash flood warning at Jun 30, 2021, 8:50 PM MDT for Weld 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: Jun 30, 2021, 8:50 PM MDT (02:50 UTC)
Expired: Jul 1, 2021, 12:00 AM MDT
In force: 3 hr
Issued by: NWS Denver/Boulder, CO
Area: Storm-based polygon
Flood severity: None

County Weld County, CO

The radar

The Cheyenne radar (KCYS), 44 km from the middle of the area, began a volume at 02:52 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
Jun 30, 10:15 PM MDT	FLASH FLOOD	9 N Purcell, CO	FLASH FLOOD ON COAL CREEK. TIME ESTIMATED. SPOTTER JUST EAST OF THIS LOCATION HAD MORE THAN 5 INCHES OF RAIN, MOSTLY BETWEEN 8 AND 10 PM.

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, 2.8 hours before the alert went out and 156 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: 4 J/kg
Mixed-layer CIN: -19 J/kg
Mixed-layer LCL: 2575 m above ground
0-6 km bulk shear: 15 kt
0-1 km storm-relative helicity: -4 m²/s²
0-3 km storm-relative helicity: 41 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

658 
WGUS55 KBOU 010250
FFWBOU
COC123-010600-
/O.NEW.KBOU.FF.W.0007.210701T0250Z-210701T0600Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Denver CO
850 PM MDT Wed Jun 30 2021

The National Weather Service in Denver has issued a

* Flash Flood Warning for...
  Northwestern Weld County in northeastern Colorado...

* Until midnight MDT.

* At 850 PM MDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 2 and 3.5 inches of 
  rain have fallen. Additional rainfall amounts of 0.5 to 1 inch are 
  possible in 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...
  mainly rural areas of Northwestern Weld County

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Be aware of your surroundings and do not drive on flooded roads.

Excessive runoff from this storm will cause flash flooding of small 
creeks and streams, country roads, farmland along creeks, and other 
low lying areas.

&&

LAT...LON 4081 10471 4082 10470 4083 10469 4084 10462
      4081 10459 4078 10452 4077 10452 4073 10457
      4072 10461 4071 10467 4075 10470

FLASH FLOOD...RADAR INDICATED

$$

Danielson

The office that day

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

Issued	Product	Office	Counties	Lasted
Jun 30, 8:20 PM MDT	Areal Flood Advisory	BOU	Weld	115 min
Jun 30, 10:32 PM MDT	Flash Flood Warning	BOU	Weld	3 hr
Jul 1, 12:56 AM MDT	Flash Flood Warning	BOU	Weld	3 hr
Jul 1, 8:46 AM MDT	Flash Flood Watch	BOU	Adams, Arapahoe, Boulder, Broomfield, Clear Creek, Denver and 7 more	12 hr
Jul 1, 11:27 AM MDT	Areal Flood Advisory	BOU	Elbert	93 min
Jul 1, 11:49 AM MDT	Flash Flood Warning	BOU	Larimer	116 min
Jul 1, 11:51 AM MDT	Areal Flood Advisory	BOU	Weld	84 min
Jul 1, 12:13 PM MDT	Flash Flood Warning	BOU	Clear Creek, Gilpin	86 min
Jul 1, 12:21 PM MDT	Areal Flood Advisory	BOU	Elbert	114 min
Jul 1, 12:24 PM MDT	Flash Flood Warning	BOU	Weld	2 hr
Jul 1, 12:28 PM MDT	Areal Flood Advisory	BOU	Weld	92 min
Jul 1, 12:30 PM MDT	Special Weather Statement	BOU	Adams	30 min
Jul 1, 12:56 PM MDT	Special Weather Statement	BOU	Adams	34 min
Jul 1, 12:58 PM MDT	Areal Flood Advisory	BOU	Grand	92 min
Jul 1, 1:05 PM MDT	Areal Flood Advisory	BOU	Adams, Weld	85 min
Jul 1, 1:12 PM MDT	Areal Flood Advisory	BOU	Weld	93 min
Jul 1, 1:25 PM MDT	Areal Flood Advisory	BOU	Douglas	95 min
Jul 1, 1:28 PM MDT	Flash Flood Warning	BOU	Weld	2 hr
Jul 1, 1:33 PM MDT	Areal Flood Advisory	BOU	Grand	87 min
Jul 1, 1:55 PM MDT	Areal Flood Advisory	BOU	Elbert	95 min
Jul 1, 2:20 PM MDT	Areal Flood Advisory	BOU	Adams, Arapahoe	3 hr
Jul 1, 2:24 PM MDT	Special Weather Statement	BOU	Arapahoe	21 min
Jul 1, 2:26 PM MDT	Severe Thunderstorm Warning	BOU	Arapahoe	34 min
Jul 1, 2:52 PM MDT	Areal Flood Advisory	BOU	Boulder, Larimer	83 min
Jul 1, 3:04 PM MDT	Areal Flood Advisory	BOU	Arapahoe	86 min
Jul 1, 3:09 PM MDT	Flash Flood Warning	BOU	Larimer	114 min
Jul 1, 3:17 PM MDT	Areal Flood Advisory	BOU	Boulder	88 min
Jul 1, 3:21 PM MDT	Flash Flood Warning	BOU	Arapahoe	114 min
Jul 1, 3:36 PM MDT	Special Weather Statement	BOU	Boulder	24 min
Jul 1, 3:51 PM MDT	Areal Flood Advisory	BOU	Larimer	84 min
Jul 1, 3:55 PM MDT	Areal Flood Advisory	BOU	Arapahoe, Denver	95 min
Jul 1, 4:03 PM MDT	Areal Flood Advisory	BOU	Boulder	87 min
Jul 1, 4:27 PM MDT	Areal Flood Advisory	BOU	Jefferson	93 min
Jul 1, 4:36 PM MDT	Flash Flood Warning	BOU	Jefferson	84 min
Jul 1, 4:42 PM MDT	Areal Flood Advisory	BOU	Larimer	93 min
Jul 1, 5:19 PM MDT	Areal Flood Advisory	BOU	Park	86 min
Jul 1, 5:57 PM MDT	Areal Flood Advisory	BOU	Jefferson, Park	93 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.