Alert archive / Wyoming / Flash Flood Warnings in 2021

Flash Flood Warning 3, NWS Riverton, WY

July 30, 2021Fremont County, Natrona County, Wyoming

NWS Riverton, WY issued this flash flood warning at Jul 30, 2021, 8:25 PM MDT for Fremont County, Natrona 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 30, 2021, 8:25 PM MDT (02:25 UTC)
Expired: Jul 30, 2021, 11:30 PM MDT
In force: 3 hr
Issued by: NWS Riverton, WY
Area: Storm-based polygon
Flood severity: None

Counties Fremont County, WY, Natrona County, WY

The radar

The Riverton/Lander radar (KRIW), 92 km from the middle of the area, began a volume at 02:25 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

Riverton, WY (KRIW), launched 00:00Z, 2.4 hours before the alert went out and 88 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.

145 
WGUS55 KRIW 310225
FFWRIW
WYC013-025-310530-
/O.NEW.KRIW.FF.W.0003.210731T0225Z-210731T0530Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

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

The National Weather Service in Riverton has issued a

* Flash Flood Warning for...
  Southeastern Fremont County in central Wyoming...
  Southwestern Natrona County in central Wyoming...

* Until 1130 PM MDT.

* At 825 PM MDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 1 and 2 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...
  Jeffrey City, Split Rock and Crooks Gap.

The drainges of most concern for flooding are Crooks Creek and the 
Sweetwater River.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Be especially cautious at night when it is harder to recognize the 
dangers of flooding.

Be aware of your surroundings and do not drive on flooded roads.

&&

LAT...LON 4259 10754 4244 10734 4244 10753 4237 10753
      4233 10786 4243 10796 4255 10788 4255 10787
      4264 10761

FLASH FLOOD...RADAR INDICATED
EXPECTED RAINFALL...0.5-1 INCH IN 1 HOUR

$$

Murrell

2 follow-up statements

284 
WGUS75 KRIW 310325
FFSRIW

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

WYC013-025-310530-
/O.CON.KRIW.FF.W.0003.000000T0000Z-210731T0530Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Fremont WY-Natrona WY-
925 PM MDT Fri Jul 30 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 1130 PM MDT THIS 
EVENING FOR SOUTHEASTERN FREMONT AND SOUTHWESTERN NATRONA COUNTIES...

At 925 PM MDT, Doppler radar indicated thunderstorms are beginning 
to move east, away from the flash food warning area of extreme 
southeast Fremont and extreme southwest Natrona County. Between 1 
and 3 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, as well as other
         drainage and low lying areas.

Some locations that will experience flash flooding include...
  Jeffrey City, Split Rock and Crooks Gap.

The drainages of most concern for flash flooding are Crooks Creek 
and Sweetwater River.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Be especially cautious at night when it is harder to recognize the 
dangers of flooding.

Be aware of your surroundings and do not drive on flooded roads.

&&

LAT...LON 4259 10754 4244 10734 4244 10753 4237 10753
      4233 10786 4243 10796 4255 10788 4255 10787
      4264 10761

FLASH FLOOD...RADAR INDICATED

$$

Murrell

624 
WGUS75 KRIW 310533
FFSRIW

Flash Flood Statement
National Weather Service Riverton WY
1133 PM MDT Fri Jul 30 2021

WYC013-025-310543-
/O.EXP.KRIW.FF.W.0003.000000T0000Z-210731T0530Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Fremont WY-Natrona WY-
1133 PM MDT Fri Jul 30 2021

...FLASH FLOOD WARNING HAS EXPIRED FOR SOUTHEASTERN FREMONT AND 
SOUTHWESTERN NATRONA COUNTIES...

Flood waters should be receding, but light rain will continue for 
the next couple of hours. Flooding is no longer expected to pose a 
threat. Please continue to heed remaining road closures.



LAT...LON 4259 10754 4244 10734 4244 10753 4237 10753
      4233 10786 4243 10796 4255 10788 4255 10787
      4264 10761

$$

Murrell

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 30, 6:18 PM MDT	Flash Flood Warning	RIW	Sweetwater	3 hr
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, 8:34 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; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.