Alert archive / Kansas / Flash Flood Warnings in 2021

Flash Flood Warning 35, NWS Kansas City, MO

August 12, 2021Johnson County, Kansas

NWS Kansas City, MO issued this flash flood warning at Aug 12, 2021, 10:03 PM CDT for Johnson County, Kansas. It was in force for 4 hr. 1 report 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: Aug 12, 2021, 10:03 PM CDT (03:03 UTC)
Expired: Aug 13, 2021, 2:00 AM CDT
In force: 4 hr
Issued by: NWS Kansas City, MO
Area: Storm-based polygon
Flood severity: None

County Johnson County, KS

The radar

The Pleasant Hill radar (KEAX), 53 km from the middle of the area, began a volume at 03:05 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
Aug 12, 10:03 PM CDT	FLASH FLOOD	2 E Olathe, KS	DELAYED REPORT. PUBLIC REPORT VIA MEDIA OF WATER OVER INTERSECTION AT SANTA FE ST. AND NORTH LINDENWOOD.

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

The nearest sounding before it

Topeka, KS (KTOP), launched 00:00Z, 3.1 hours before the alert went out and 68 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: 4214 J/kg
Mixed-layer CIN: -86 J/kg
Mixed-layer LCL: 1420 m above ground
0-6 km bulk shear: 14 kt
0-1 km storm-relative helicity: 110 m²/s²
0-3 km storm-relative helicity: 179 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 6.4

Open this sounding in Storm Lab

The text

As transmitted.

953 
WGUS53 KEAX 130303
FFWEAX
KSC091-130700-
/O.NEW.KEAX.FF.W.0035.210813T0303Z-210813T0700Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Kansas City/Pleasant Hill MO
1003 PM CDT Thu Aug 12 2021

The National Weather Service in Pleasant Hill has issued a

* Flash Flood Warning for...
  Johnson County in east central Kansas...

* Until 200 AM CDT.

* At 1002 PM CDT, Doppler radar indicated thunderstorms producing
  heavy rain across the warned area. Up to two inches of rain have 
  already fallen, with an additional 1 to 2 inches possible. Flash 
  flooding is ongoing or expected to begin shortly.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Radar indicated.

  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 flooding include...
  Overland Park, Olathe, Shawnee, Lenexa, Leawood, Prairie Village,
  Gardner, Merriam, De Soto, Spring Hill, Clare, Lackmans, Stillwell
  and Stanley.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3899 9495 3899 9492 3898 9492 3899 9491
      3900 9461 3876 9461 3879 9501

FLASH FLOOD...RADAR INDICATED

$$

Blair

1 follow-up statement

257 
WGUS73 KEAX 130420
FFSEAX

Flash Flood Statement
National Weather Service Kansas City/Pleasant Hill MO
1120 PM CDT Thu Aug 12 2021

KSC091-130700-
/O.CON.KEAX.FF.W.0035.000000T0000Z-210813T0700Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Johnson KS-
1120 PM CDT Thu Aug 12 2021

...THE FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 200 AM CDT FOR
JOHNSON COUNTY...

At 1113 PM CDT, Doppler radar indicated thunderstorms producing 
heavy rain across the warned area. Over five inches of rain have 
already fallen in portions of the county in a short period of time. 
The greatest areas of rain have fallen over portions of Olathe 
and Lenexa. Flash flooding is ongoing or expected to begin shortly.

HAZARD...Life threatening flash flooding. Heavy rain producing flash 
         flooding.

SOURCE...Radar indicated.

IMPACT...Life threatening flash flooding of creeks and streams, 
         urban areas, highways, streets and underpasses.

Some locations that will experience flooding include...
Overland Park, Olathe, Shawnee, Lenexa, Leawood, Prairie Village,
Gardner, Merriam, De Soto, Spring Hill, Clare, Lackmans, Stillwell
and Stanley.

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 3899 9495 3899 9492 3898 9492 3899 9491
      3900 9461 3876 9461 3879 9501

FLASH FLOOD...RADAR INDICATED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE

$$

Blair

The office that day

Everything else NWS Kansas City, MO issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 12, 7:32 PM CDT	Special Weather Statement	EAX	Wyandotte	28 min
Aug 12, 8:03 PM CDT	Special Weather Statement	EAX	Johnson, Wyandotte	27 min
Aug 12, 8:16 PM CDT	Severe Thunderstorm Warning	EAX	Johnson, Wyandotte	29 min
Aug 12, 8:45 PM CDT	Special Weather Statement	EAX	Johnson	30 min
Aug 12, 9:06 PM CDT	Severe Thunderstorm Warning	EAX	Johnson	24 min
Aug 12, 9:29 PM CDT	Severe Thunderstorm Warning	EAX	Johnson, Miami	31 min
Aug 12, 9:36 PM CDT	Severe Thunderstorm Warning	EAX	Johnson, Leavenworth, Wyandotte	24 min
Aug 12, 9:52 PM CDT	Severe Thunderstorm Warning	EAX	Johnson	23 min
Aug 12, 9:55 PM CDT	Severe Thunderstorm Warning	EAX	Johnson, Leavenworth, Wyandotte	20 min
Aug 12, 10:16 PM CDT	Special Weather Statement	EAX	Johnson	29 min
Aug 12, 11:39 PM CDT	River Flood Warning	EAX	Johnson	4 hr
Aug 12, 11:39 PM CDT	River Flood Warning	EAX	Johnson	8 hr
Aug 12, 11:39 PM CDT	River Flood Warning	EAX	Johnson	18 hr
Aug 12, 11:57 PM CDT	Severe Thunderstorm Warning	EAX	Linn, Miami	33 min
Aug 13, 12:42 AM CDT	Special Weather Statement	EAX	Atchison	33 min
Aug 13, 1:57 AM CDT	Flash Flood Warning	EAX	Johnson, Leavenworth, Wyandotte	6 hr
Aug 13, 5:49 AM CDT	Areal Flood Warning	EAX	Linn, Miami	12 hr
Aug 13, 7:39 AM CDT	Areal Flood Warning	EAX	Johnson, Leavenworth, Wyandotte	10 hr

Nearby

Flash Flood Warnings in Kansas, 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.