Alert archive / Wyoming / Flash Flood Warnings in 2021

Flash Flood Warning 2, NWS Riverton, WY

July 30, 2021Sweetwater County, Wyoming

NWS Riverton, WY issued this flash flood warning at Jul 30, 2021, 6:18 PM MDT for Sweetwater County, Wyoming. It was in force for 3 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, 6:18 PM MDT (00:18 UTC)
Expired: Jul 30, 2021, 9:15 PM MDT
In force: 3 hr
Issued by: NWS Riverton, WY
Area: Storm-based polygon
Flood severity: None

County Sweetwater County, WY

The radar

The Riverton/Lander radar (KRIW), 175 km from the middle of the area, began a volume at 00:19 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, 7:05 PM MDT	FLASH FLOOD	Rock Springs, WY	FLOODWATERS OVERFLOWED STORM DRAINAGE SYSTEM AND FORCED MANHOLE COVERS OFF IN SOUTHERN PART OF TOWN AROUND D AND REED STREETS AS WELL AS C AND PINE STREETS.
Jul 30, 7:05 PM MDT	FLASH FLOOD	Rock Springs, WY	FLOODWATERS OVERFLOWED STORMWATER DRAINAGE SYSTEM IN SOUTHERN PART OF TOWN TO FORCE MANHOLE COVERS OFF AROUND D AND REED STREETS AS WELL AS C AND PINE STREETS.
Jul 30, 7:05 PM MDT	FLASH FLOOD	Rock Springs, WY	FOOD WATERS OVERFLOWER STORM DRAINAGE SYSTEM AND FORCED MANHOLE COVERS OFF IN THE SOUTHERN PART OF TOWN AROUND D AND REED STREETS AS WELL AS C AND PINE STREETS.

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The nearest sounding before it

Riverton, WY (KRIW), launched 00:00Z, 0.3 hours before the alert went out and 178 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: 8 J/kg
Mixed-layer CIN: -124 J/kg
Mixed-layer LCL: 1855 m above ground
0-6 km bulk shear: 14 kt
0-1 km storm-relative helicity: 8 m²/s²
0-3 km storm-relative helicity: 104 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

558 
WGUS55 KRIW 310018
FFWRIW
WYC037-310315-
/O.NEW.KRIW.FF.W.0002.210731T0018Z-210731T0315Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

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

The National Weather Service in Riverton has issued a

* Flash Flood Warning for...
  Central Sweetwater County in south central Wyoming...

* Until 915 PM MDT.

* At 618 PM MDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the Rock Springs area. Flash flooding is ongoing 
  or expected to begin shortly.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Radar.

  IMPACT...Flooding of small creeks and streams, urban areas,
           highways, streets and underpasses as well as other
           drainage and low lying areas.

* Some locations that will experience flash flooding include...
  Rock Springs and Sweetwater County Fairgrounds.

This includes the following highways...
	Interstate 80 between mile markers 102 and 108.

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 4154 10927 4166 10929 4166 10918 4156 10917

FLASH FLOOD...RADAR INDICATED

$$

Murrell

2 follow-up statements

165 
WGUS75 KRIW 310134
FFSRIW

Flash Flood Statement
National Weather Service Riverton WY
734 PM MDT Fri Jul 30 2021

WYC037-310315-
/O.CON.KRIW.FF.W.0002.000000T0000Z-210731T0315Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Sweetwater WY-
734 PM MDT Fri Jul 30 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 915 PM MDT THIS 
EVENING FOR CENTRAL SWEETWATER COUNTY...

At 734 PM MDT, Doppler radar indicated thunderstorms producing heavy 
rain across the warned area. Between 0.25 and 0.5 inches of rain 
have fallen. Flash flooding is ongoing or expected to begin shortly.

HAZARD...Flash flooding caused by thunderstorms.

SOURCE...Radar.

IMPACT...Flooding of small creeks and streams, urban areas,
         highways, streets and underpasses as well as other
         drainage and low lying areas.

Some locations that will experience flash flooding include...
  Rock Springs and Sweetwater County Fairgrounds.

This includes the following highways...
	Interstate 80 between mile markers 102 and 108.

Thunderstorms continue to form south and southwest of Rock Springs. 
These thunderstorms are generally moving northward between 10 and 15 
mph.

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 4154 10927 4166 10929 4166 10918 4156 10917

FLASH FLOOD...RADAR INDICATED

$$

Murrell

290 
WGUS75 KRIW 310311
FFSRIW

Flash Flood Statement
National Weather Service Riverton WY
911 PM MDT Fri Jul 30 2021

WYC037-310321-
/O.EXP.KRIW.FF.W.0002.000000T0000Z-210731T0315Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Sweetwater WY-
911 PM MDT Fri Jul 30 2021

...FLASH FLOOD WARNING WILL EXPIRE AT 915 PM MDT THIS EVENING FOR 
CENTRAL SWEETWATER COUNTY...

The heavy rain has ended. Some light rain is possible over the next 
hour. Currently, additional rainfall is expected to be minimal for 
the rest of the night. Thus flooding is no longer expected to pose a 
threat.

A Flash Flood Watch remains in effect until 600 PM MDT Saturday for 
portions of central Wyoming, northwest Wyoming, south central 
Wyoming, southwest Wyoming and west central Wyoming.

LAT...LON 4154 10927 4166 10929 4166 10918 4156 10917

$$

Murrell

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 30, 6:31 PM MDT	Areal Flood Advisory	RIW	Natrona	119 min
Jul 30, 7:18 PM MDT	Special Weather Statement	RIW		27 min
Jul 30, 7:56 PM MDT	Special Weather Statement	RIW		34 min
Jul 30, 8:25 PM MDT	Flash Flood Warning	RIW	Fremont, Natrona	3 hr
Jul 30, 8:34 PM MDT	Special Weather Statement	RIW		26 min
Jul 30, 8:45 PM MDT	Special Weather Statement	RIW	Johnson	30 min
Jul 30, 9:45 PM MDT	Special Weather Statement	RIW	Fremont	30 min
Jul 31, 1:41 PM MDT	Areal Flood Advisory	RIW	Big Horn	3 hr
Jul 31, 3:26 PM MDT	Special Weather Statement	RIW	Lincoln	34 min
Jul 31, 3:31 PM MDT	Special Weather Statement	RIW		29 min
Jul 31, 3:48 PM MDT	Areal Flood Advisory	RIW	Lincoln	36 min
Jul 31, 3:58 PM MDT	Special Weather Statement	RIW	Fremont	32 min
Jul 31, 4:10 PM MDT	Flash Flood Warning	RIW	Lincoln	4 hr
Jul 31, 4:21 PM MDT	Special Weather Statement	RIW	Lincoln	24 min
Jul 31, 4:45 PM MDT	Areal Flood Advisory	RIW	Fremont	60 min
Jul 31, 5:03 PM MDT	Special Weather Statement	RIW	Teton	42 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.