Alert archive / North Dakota / Flash Flood Warnings in 2021

Flash Flood Warning 6, NWS Bismarck, ND

August 7, 2021Sioux County, North Dakota

NWS Bismarck, ND issued this flash flood warning at Aug 7, 2021, 4:11 PM CDT for Sioux County, North Dakota. 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: Aug 7, 2021, 4:11 PM CDT (21:11 UTC)
Expired: Aug 7, 2021, 7:15 PM CDT
In force: 3 hr
Issued by: NWS Bismarck, ND
Area: Storm-based polygon
Flood severity: None

County Sioux County, ND

The radar

The Bismarck radar (KBIS), 66 km from the middle of the area, began a volume at 21:11 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

Bismarck Municip, ND (KBIS), launched 12:00Z, 9.2 hours before the alert went out and 67 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: 309 J/kg
Mixed-layer CIN: -183 J/kg
Mixed-layer LCL: 993 m above ground
0-6 km bulk shear: 9 kt
0-1 km storm-relative helicity: 54 m²/s²
0-3 km storm-relative helicity: 58 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

736 
WGUS53 KBIS 072111
FFWBIS
NDC085-080015-
/O.NEW.KBIS.FF.W.0006.210807T2111Z-210808T0015Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Bismarck ND
411 PM CDT Sat Aug 7 2021

The National Weather Service in Bismarck has issued a

* Flash Flood Warning for...
  East Central Sioux County in south central North Dakota...

* Until 715 PM CDT /615 PM MDT/.

* At 411 PM CDT /311 PM MDT/, Doppler radar indicated thunderstorms 
  producing heavy rain across the warned area. Between 2 and 5 
  inches of rain have fallen. 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, highways,
           county roads, as well as other poor drainage and low-
           lying areas.

* Some locations that will experience flash flooding include...
  Mainly rural areas of East Central Sioux County north of Selfridge 
  and west of Fort Yates.

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 4606 10079 4609 10100 4617 10107 4626 10101
      4628 10099 4629 10091 4623 10071 4617 10067

FLASH FLOOD...RADAR INDICATED

$$

CJS

2 follow-up statements

021 
WGUS73 KBIS 072235
FFSBIS

Flash Flood Statement
National Weather Service Bismarck ND
535 PM CDT Sat Aug 7 2021

NDC085-080015-
/O.CON.KBIS.FF.W.0006.000000T0000Z-210808T0015Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Sioux ND-
535 PM CDT Sat Aug 7 2021 /435 PM MDT Sat Aug 7 2021/

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 715 PM CDT/615 PM 
MDT/ THIS EVENING FOR EAST CENTRAL SIOUX COUNTY...

At 535 PM CDT /435 PM MDT/, Doppler radar indicated heavy rain 
across the warned area, with radar estimating that between 3 and 6 
inches of rain have fallen. Flash flooding is ongoing or expected to 
begin shortly.

HAZARD...Flash flooding caused by heavy rain.

SOURCE...Radar.

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

Some locations that will experience flash flooding include...
  Mainly rural areas of East Central Sioux County north of Selfridge 
  and west of Fort Yates.

Up to an inch of additional rain is possible through early evening.

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 4606 10079 4609 10100 4617 10107 4626 10101
      4628 10099 4629 10091 4623 10071 4617 10067

FLASH FLOOD...RADAR INDICATED

$$

CJS

447 
WGUS73 KBIS 080020
FFSBIS

Flash Flood Statement
National Weather Service Bismarck ND
720 PM CDT Sat Aug 7 2021

NDC085-080030-
/O.EXP.KBIS.FF.W.0006.000000T0000Z-210808T0015Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Sioux ND-
720 PM CDT Sat Aug 7 2021 /620 PM MDT Sat Aug 7 2021/

...FLASH FLOOD WARNING HAS EXPIRED FOR EAST CENTRAL SIOUX COUNTY...

The heavy rain has ended. However, please continue to heed any road 
closures.

LAT...LON 4606 10079 4609 10100 4617 10107 4626 10101
      4628 10099 4629 10091 4623 10071 4617 10067

$$

CJS

The office that day

Everything else NWS Bismarck, ND issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 7, 2:31 AM CDT	Special Weather Statement	BIS	Billings	44 min
Aug 7, 5:23 AM CDT	Special Weather Statement	BIS	Stark	52 min
Aug 7, 6:46 AM CDT	Special Weather Statement	BIS	Hettinger	44 min
Aug 7, 8:55 AM CDT	Special Weather Statement	BIS	Adams	35 min
Aug 7, 9:25 AM CDT	Special Weather Statement	BIS	Grant	35 min
Aug 7, 2:53 PM CDT	Areal Flood Advisory	BIS	Grant, Morton, Sioux	3 hr
Aug 7, 6:42 PM CDT	Special Weather Statement	BIS	Dickey	33 min

Nearby

Flash Flood Warnings in North Dakota, 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.