Alert archive / Wyoming / Flash Flood Warnings in 2021

Flash Flood Warning 11, NWS Cheyenne, WY

August 15, 2021Albany County, Wyoming

NWS Cheyenne, WY issued this flash flood warning at Aug 15, 2021, 4:46 PM MDT for Albany County, Wyoming. It was in force for 95 min. 3 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 15, 2021, 4:46 PM MDT (22:46 UTC)
Expired: Aug 15, 2021, 6:21 PM MDT
In force: 95 min
Issued by: NWS Cheyenne, WY
Area: Storm-based polygon
Damage threat: Considerable
Flood severity: None

County Albany County, WY

The radar

The Cheyenne radar (KCYS), 72 km from the middle of the area, began a volume at 22:48 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 15, 4:56 PM MDT	FLASH FLOOD	N Laramie, WY
Aug 15, 5:03 PM MDT	FLASH FLOOD	1 Se Laramie, WY	STREETS FLOODED.SPRING CREEK OUT OF ITS BANKS AND THIRD OF WAY UP FLOOD CONTROL LEVIES.0.86INCHES OF RAIN SO FAR.
Aug 15, 5:12 PM MDT	FLASH FLOOD	Laramie, WY	NUMEROUS REPORTS OF BASEMENTS 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 12:00Z, 10.8 hours before the alert went out and 259 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: 37 J/kg
Mixed-layer CIN: -475 J/kg
Mixed-layer LCL: 2654 m above ground
0-6 km bulk shear: 14 kt
0-1 km storm-relative helicity: -57 m²/s²
0-3 km storm-relative helicity: -14 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

938 
WGUS55 KCYS 152246
FFWCYS
WYC001-160145-
/O.NEW.KCYS.FF.W.0011.210815T2246Z-210816T0145Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Cheyenne WY
446 PM MDT Sun Aug 15 2021

The National Weather Service in Cheyenne has issued a

* Flash Flood Warning for...
  Southeastern Albany County in southeastern Wyoming...

* Until 745 PM MDT.

* At 446 PM MDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Flash flooding is ongoing or 
  expected to begin shortly.

  HAZARD...Life threatening flash flooding caused by
           thunderstorms.

  SOURCE...Radar.

  IMPACT...Life threatening flash flooding of creeks and streams,
           urban areas, highways, streets and underpasses.

* Some locations that will experience flash flooding include...
  Laramie, University Of Wyoming War Memorial Stadium, The Buttes, 
  Tie City Campground and Yellow Pine Campground.

This includes the following highways...
	Interstate 80 in Wyoming between mile markers 297 and 326.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4151 10557 4134 10544 4122 10539 4113 10549
      4108 10560 4113 10570 4125 10573 4135 10580
      4145 10586 4149 10587

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

$$

Claycomb

1 follow-up statement

558 
WGUS75 KCYS 160021
FFSCYS

Flash Flood Statement
National Weather Service Cheyenne WY
621 PM MDT Sun Aug 15 2021

WYC001-160031-
/O.CAN.KCYS.FF.W.0011.000000T0000Z-210816T0145Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Albany WY-
621 PM MDT Sun Aug 15 2021

...FLASH FLOOD WARNING IS CANCELLED FOR SOUTHEASTERN ALBANY COUNTY...

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

LAT...LON 4151 10557 4134 10544 4122 10539 4113 10549
      4108 10560 4113 10570 4125 10573 4135 10580
      4145 10586 4149 10587

$$

Claycomb

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 14, 7:01 PM MDT	Severe Thunderstorm Warning	CYS	Laramie	44 min
Aug 14, 7:12 PM MDT	Severe Thunderstorm Warning Considerable damage threat	CYS	Laramie	48 min
Aug 14, 7:36 PM MDT	Severe Thunderstorm Warning	CYS	Laramie	39 min
Aug 15, 12:42 PM MDT	Areal Flood Advisory	CYS	Albany, Carbon	3 hr
Aug 15, 1:03 PM MDT	Special Weather Statement	CYS	Platte	42 min
Aug 15, 1:06 PM MDT	Areal Flood Advisory	CYS	Albany	3 hr
Aug 15, 1:42 PM MDT	Areal Flood Advisory	CYS	Albany, Carbon, Converse	2 hr
Aug 15, 2:10 PM MDT	Special Weather Statement	CYS	Albany	35 min
Aug 15, 2:21 PM MDT	Special Weather Statement	CYS	Albany	24 min
Aug 15, 3:47 PM MDT	Special Weather Statement	CYS	Albany	28 min
Aug 15, 3:49 PM MDT	Special Weather Statement	CYS	Albany	26 min
Aug 15, 4:25 PM MDT	Special Weather Statement	CYS	Albany	50 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.