Alert archive / Wyoming / Flash Flood Warnings in 2021

Flash Flood Warning 4, NWS Cheyenne, WY

July 1, 2021Laramie County, Wyoming

NWS Cheyenne, WY issued this flash flood warning at Jul 1, 2021, 3:59 PM MDT for Laramie County, Wyoming. It was in force for 3 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 1, 2021, 3:59 PM MDT (21:59 UTC)
Expired: Jul 1, 2021, 7:00 PM MDT
In force: 3 hr
Issued by: NWS Cheyenne, WY
Area: Storm-based polygon
Flood severity: None

County Laramie County, WY

The radar

The Cheyenne radar (KCYS), 49 km from the middle of the area, began a volume at 22:02 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, 10.0 hours before the alert went out and 235 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: 240 J/kg
Mixed-layer CIN: -180 J/kg
Mixed-layer LCL: 1308 m above ground
0-6 km bulk shear: 11 kt
0-1 km storm-relative helicity: 17 m²/s²
0-3 km storm-relative helicity: 9 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

682 
WGUS55 KCYS 012159
FFWCYS
WYC021-020100-
/O.NEW.KCYS.FF.W.0004.210701T2159Z-210702T0100Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Cheyenne WY
359 PM MDT Thu Jul 1 2021

The National Weather Service in Cheyenne has issued a

* Flash Flood Warning for...
  North Central Laramie County in southeastern Wyoming...

* Until 700 PM MDT.

* At 359 PM MDT, Doppler radar indicated thunderstorms producing 
  heavy rain in along Bear Creek in north central Laramie County. 
  Very heavy rainfall is also occurring along Interstate 25 north of 
  Whitaker. Between 2 and 3 inches of rain have 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...Flash flooding caused by thunderstorms.

  SOURCE...Radar.

  IMPACT...Flash flooding of small creeks and streams, urban
           areas, highways, streets and underpasses as well as
           other poor drainage and low-lying areas.

* Some locations that will experience flash flooding include...
  mainly rural areas of North Central Laramie County, especially 
  along Bear Creek.

This includes the following highways...
	Interstate 25 in Wyoming between mile markers 40 and 47.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4154 10498 4157 10501 4160 10500 4165 10497
      4165 10466 4161 10466 4160 10470 4161 10474
      4161 10477 4159 10479 4155 10488

FLASH FLOOD...RADAR INDICATED

$$

Hammer

1 follow-up statement

121 
WGUS75 KCYS 020055
FFSCYS

Flash Flood Statement
National Weather Service Cheyenne WY
655 PM MDT Thu Jul 1 2021

WYC021-020105-
/O.EXP.KCYS.FF.W.0004.000000T0000Z-210702T0100Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Laramie WY-
655 PM MDT Thu Jul 1 2021

...FLASH FLOOD WARNING WILL EXPIRE AT 7 PM MDT THIS EVENING FOR 
NORTH CENTRAL LARAMIE COUNTY...

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

LAT...LON 4154 10498 4157 10501 4160 10500 4165 10497
      4165 10466 4161 10466 4160 10470 4161 10474
      4161 10477 4159 10479 4155 10488

$$

Hammer

The office that day

Everything else NWS Cheyenne, WY issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 1, 1:12 PM MDT	Special Weather Statement	CYS	Albany	48 min
Jul 1, 1:14 PM MDT	Areal Flood Advisory	CYS	Goshen	3 hr
Jul 1, 2:38 PM MDT	Special Weather Statement	CYS	Laramie	37 min
Jul 1, 2:57 PM MDT	Special Weather Statement	CYS	Laramie	48 min

Nearby

Flash Flood Warnings in Wyoming, 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.