Alert archive / Wyoming / Flash Flood Warnings in 2021

Flash Flood Warning 10, NWS Cheyenne, WY

July 30, 2021Laramie County, Platte County, Wyoming

NWS Cheyenne, WY issued this flash flood warning at Jul 30, 2021, 5:46 PM MDT for Laramie County, Platte County, Wyoming. It was in force for 2 hr. 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: Jul 30, 2021, 5:46 PM MDT (23:46 UTC)
Expired: Jul 30, 2021, 8:13 PM MDT
In force: 2 hr
Issued by: NWS Cheyenne, WY
Area: Storm-based polygon
Flood severity: None

Counties Laramie County, WY, Platte County, WY

The radar

The Cheyenne radar (KCYS), 62 km from the middle of the area, began a volume at 23:49 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
Jul 30, 5:50 PM MDT	FLASH FLOOD	Chugwater, WY	IRON MOUNTAIN RD FLOODED.
Jul 30, 5:54 PM MDT	FLASH FLOOD	2 Ssw Chugwater, WY	2.40 INCHES OF RAIN.
Jul 30, 6:41 PM MDT	HEAVY RAIN 3.37	3 S Chugwater, WY	TOTAL OF 3.37 INCHES OF RAINFALL FROM LOCAL WEATHER STATION.

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, 11.8 hours before the alert went out and 251 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 2523 m above ground
0-6 km bulk shear: 18 kt
0-1 km storm-relative helicity: -18 m²/s²
0-3 km storm-relative helicity: 2 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

317 
WGUS55 KCYS 302346
FFWCYS
WYC021-031-310245-
/O.NEW.KCYS.FF.W.0010.210730T2346Z-210731T0245Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Cheyenne WY
546 PM MDT Fri Jul 30 2021

The National Weather Service in Cheyenne has issued a

* Flash Flood Warning for...
  Northern Laramie County in southeastern Wyoming...
  South Central Platte County in southeastern Wyoming...

* Until 845 PM MDT.

* At 546 PM MDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 1 and 2 inches of rain 
  have fallen. Additional rainfall amounts of 1 to 1.5 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...
  Chugwater.

This includes the following highways...
	Interstate 25 in Wyoming between mile markers 49 and 57.

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.

&&

LAT...LON 4166 10515 4173 10506 4178 10494 4179 10481
      4175 10474 4168 10483 4161 10500 4161 10512

FLASH FLOOD...RADAR INDICATED

$$

Brothers

1 follow-up statement

212 
WGUS75 KCYS 310213
FFSCYS

Flash Flood Statement
National Weather Service Cheyenne WY
813 PM MDT Fri Jul 30 2021

WYC021-031-310223-
/O.CAN.KCYS.FF.W.0010.000000T0000Z-210731T0245Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Laramie WY-Platte WY-
813 PM MDT Fri Jul 30 2021

...FLASH FLOOD WARNING IS CANCELLED FOR NORTHERN LARAMIE AND SOUTH 
CENTRAL PLATTE COUNTIES...

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.

A Flash Flood Watch remains in effect until 1200 AM MDT for portions 
of south central Wyoming and southeast Wyoming.

LAT...LON 4166 10515 4173 10506 4178 10494 4179 10481
      4175 10474 4168 10483 4161 10500 4161 10512

$$

Hammer

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 29, 7:44 PM MDT	Areal Flood Advisory	CYS	Albany, Carbon	89 min
Jul 29, 10:21 PM MDT	Special Weather Statement	CYS	Converse	39 min
Jul 29, 11:06 PM MDT	Special Weather Statement	CYS	Converse	39 min
Jul 29, 11:44 PM MDT	Special Weather Statement	CYS	Converse	46 min
Jul 30, 12:29 AM MDT	Special Weather Statement	CYS	Converse, Niobrara	61 min
Jul 30, 12:54 AM MDT	Areal Flood Advisory	CYS	Niobrara	3 hr
Jul 30, 12:57 AM MDT	Special Weather Statement	CYS	Converse	33 min
Jul 30, 1:29 AM MDT	Special Weather Statement	CYS	Converse	31 min
Jul 30, 2:05 AM MDT	Special Weather Statement	CYS	Niobrara	25 min
Jul 30, 3:15 PM MDT	Special Weather Statement	CYS	Laramie	45 min
Jul 30, 3:22 PM MDT	Areal Flood Advisory	CYS	Albany, Laramie	113 min
Jul 30, 3:33 PM MDT	Flash Flood Warning	CYS	Albany, Carbon	3 hr
Jul 30, 3:48 PM MDT	Special Weather Statement	CYS	Platte	27 min
Jul 30, 4:38 PM MDT	Special Weather Statement	CYS	Platte	37 min
Jul 30, 4:51 PM MDT	Special Weather Statement	CYS	Albany	39 min
Jul 30, 5:19 PM MDT	Special Weather Statement	CYS	Platte	41 min
Jul 30, 5:23 PM MDT	Severe Thunderstorm Warning	CYS	Laramie, Platte	37 min
Jul 30, 5:52 PM MDT	Special Weather Statement	CYS	Converse	38 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.