Alert archive / South Dakota / Flash Flood Warnings in 2021

Flash Flood Warning 4, NWS Aberdeen, SD

August 31, 2021Lyman County, South Dakota

NWS Aberdeen, SD issued this flash flood warning at Aug 31, 2021, 12:14 AM CDT for Lyman County, South Dakota. It was in force for 6 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 31, 2021, 12:14 AM CDT (05:14 UTC)
Expired: Aug 31, 2021, 6:15 AM CDT
In force: 6 hr
Issued by: NWS Aberdeen, SD
Area: Storm-based polygon
Flood severity: None

County Lyman County, SD

The radar

The Aberdeen radar (KABR), 211 km from the middle of the area, began a volume at 05:15 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

Aberdeen, SD (KABR), launched 00:00Z, 5.2 hours before the alert went out and 159 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: 205 J/kg
Mixed-layer CIN: -60 J/kg
Mixed-layer LCL: 1953 m above ground
0-6 km bulk shear: 46 kt
0-1 km storm-relative helicity: 34 m²/s²
0-3 km storm-relative helicity: 126 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.3

Open this sounding in Storm Lab

The text

As transmitted.

179 
WGUS53 KABR 310514
FFWABR
SDC085-311115-
/O.NEW.KABR.FF.W.0004.210831T0514Z-210831T1115Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Aberdeen SD
1214 AM CDT Tue Aug 31 2021

The National Weather Service in Aberdeen has issued a

* Flash Flood Warning for...
  East Central Lyman County in central South Dakota...

* Until 615 AM CDT Tuesday.

* At 1214 AM CDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 3 and 5 inches of rain 
  have fallen. Additional rainfall amounts up to 1 inch 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...
  Oacoma, Reliance, Lyman, Dude Ranch and Lake Francis Case.

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.

&&

LAT...LON 4373 9978 4379 9987 4385 9991 4390 9975
      4387 9931 4386 9931 4379 9937 4377 9941
      4375 9942 4374 9964 4376 9964 4377 9966
      4373 9966 4373 9969 4375 9968 4376 9970
      4373 9971 4373 9974 4375 9975

FLASH FLOOD...RADAR INDICATED

$$

Lueck

The office that day

Everything else NWS Aberdeen, SD issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 30, 11:10 PM CDT	Severe Thunderstorm Warning	ABR	Jones	25 min
Aug 30, 11:14 PM CDT	Severe Thunderstorm Warning	ABR	Hughes, Lyman	20 min
Aug 30, 11:46 PM CDT	Areal Flood Warning	ABR	Lyman	37 min
Aug 31, 12:33 AM CDT	Severe Thunderstorm Warning	ABR	Jones, Lyman	42 min

Nearby

Flash Flood Warnings in South 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.