Alert archive / Colorado / Flash Flood Warnings in 2021

Flash Flood Warning 18, NWS Denver/Boulder, CO

July 3, 2021Logan County, Colorado

NWS Denver/Boulder, CO issued this flash flood warning at Jul 3, 2021, 6:00 PM MDT for Logan County, Colorado. It was in force for 2 hr. 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 3, 2021, 6:00 PM MDT (00:00 UTC)
Expired: Jul 3, 2021, 8:00 PM MDT
In force: 2 hr
Issued by: NWS Denver/Boulder, CO
Area: Storm-based polygon
Flood severity: None

County Logan County, CO

The radar

The Goodland radar (KGLD), 170 km from the middle of the area, began a volume at 00:00 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 00:00Z, 0.0 hours before the alert went out and 100 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: 53 J/kg
Mixed-layer CIN: -81 J/kg
Mixed-layer LCL: 2871 m above ground
0-6 km bulk shear: 26 kt
0-1 km storm-relative helicity: -17 m²/s²
0-3 km storm-relative helicity: 50 m²/s²
Significant tornado parameter: 0.0
Supercell composite: -0.0

Open this sounding in Storm Lab

The text

As transmitted.

548 
WGUS55 KBOU 040000
FFWBOU
COC075-040200-
/O.NEW.KBOU.FF.W.0018.210704T0000Z-210704T0200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Denver CO
600 PM MDT Sat Jul 3 2021

The National Weather Service in Denver has issued a

* Flash Flood Warning for...
  Southeastern Logan County in northeastern Colorado...

* Until 800 PM MDT.

* At 600 PM MDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 2.5 and 3.5 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...
  Fleming, St Petersburg and Dailey.

This includes the following streams and drainages...
  Wildhorse Creek, Sandy Creek, North Fork Frenchman Creek and 
  Patent Creek.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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 4079 10295 4079 10265 4077 10265 4076 10265
      4075 10265 4071 10265 4071 10266 4069 10266
      4067 10266 4063 10267 4061 10267 4053 10267
      4050 10267 4051 10294

FLASH FLOOD...RADAR INDICATED

$$

RPK

2 follow-up statements

579 
WGUS75 KBOU 040044
FFSBOU

Flash Flood Statement
National Weather Service Denver CO
644 PM MDT Sat Jul 3 2021

COC075-040200-
/O.CON.KBOU.FF.W.0018.000000T0000Z-210704T0200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Logan CO-
644 PM MDT Sat Jul 3 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 8 PM MDT THIS EVENING 
FOR SOUTHEASTERN LOGAN COUNTY...

At 644 PM MDT, Doppler radar indicated thunderstorms had produced 
heavy rain across the warned area earlier. Between 2.5 and 3.5 
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...
  Fleming, St Petersburg and Dailey.

This includes the following streams and drainages...
  Wildhorse Creek, Sandy Creek, North Fork Frenchman Creek and 
  Patent Creek.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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 4079 10295 4079 10265 4077 10265 4076 10265
      4075 10265 4071 10265 4071 10266 4069 10266
      4067 10266 4063 10267 4061 10267 4053 10267
      4050 10267 4051 10294

FLASH FLOOD...RADAR INDICATED

$$

RPK

596 
WGUS75 KBOU 040151
FFSBOU

Flash Flood Statement
National Weather Service Denver CO
751 PM MDT Sat Jul 3 2021

COC075-040201-
/O.EXP.KBOU.FF.W.0018.000000T0000Z-210704T0200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Logan CO-
751 PM MDT Sat Jul 3 2021

...FLASH FLOOD WARNING WILL EXPIRE AT 8 PM MDT THIS EVENING FOR 
SOUTHEASTERN LOGAN COUNTY...

The heavy rain has ended. Flooding is no longer expected to pose a 
threat. Please continue to heed remaining road closures.

LAT...LON 4079 10295 4079 10265 4077 10265 4076 10265
      4075 10265 4071 10265 4071 10266 4069 10266
      4067 10266 4063 10267 4061 10267 4053 10267
      4050 10267 4051 10294

$$

RPK

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 3, 6:01 PM MDT	Areal Flood Advisory	BOU	Washington	89 min
Jul 3, 6:14 PM MDT	Special Weather Statement	BOU	Sedgwick	31 min
Jul 3, 7:26 PM MDT	Special Weather Statement	BOU	Lincoln	34 min
Jul 4, 10:34 AM MDT	Areal Flood Advisory	BOU	Larimer	86 min
Jul 4, 11:54 AM MDT	Areal Flood Advisory	BOU	Larimer	81 min
Jul 4, 12:10 PM MDT	Special Weather Statement	BOU	Larimer	50 min
Jul 4, 12:28 PM MDT	Areal Flood Advisory	BOU	Larimer	77 min
Jul 4, 12:37 PM MDT	Severe Thunderstorm Warning	BOU	Larimer	38 min
Jul 4, 1:51 PM MDT	Areal Flood Advisory	BOU	Larimer	75 min
Jul 4, 2:49 PM MDT	Special Weather Statement	BOU	Denver	26 min
Jul 4, 3:20 PM MDT	Flash Flood Warning Considerable damage threat	BOU	Larimer	85 min
Jul 4, 3:31 PM MDT	Areal Flood Advisory	BOU	Douglas	119 min
Jul 4, 3:56 PM MDT	Areal Flood Advisory	BOU	Elbert	53 min
Jul 4, 4:28 PM MDT	Special Weather Statement	BOU	Adams, Arapahoe	62 min
Jul 4, 4:43 PM MDT	Special Weather Statement	BOU	Elbert	62 min
Jul 4, 5:42 PM MDT	Special Weather Statement	BOU	Douglas	48 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.