Alert archive / Delaware / Flash Flood Warnings in 2021

Flash Flood Warning 32, NWS Philadelphia/Mount Holly

August 9, 2021Kent County, Sussex County, Delaware

NWS Philadelphia/Mount Holly issued this flash flood warning at Aug 9, 2021, 3:01 PM EDT for Kent County, Sussex County, Delaware. It was in force for 2 hr. 2 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: Aug 9, 2021, 3:01 PM EDT (19:01 UTC)
Expired: Aug 9, 2021, 5:17 PM EDT
In force: 2 hr
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Flood severity: None

Counties Kent County, DE, Sussex County, DE

The radar

The Dover AFB radar (KDOX), 2 km from the middle of the area, began a volume at 19:00 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 9, 3:44 PM EDT	FLASH FLOOD	Harrington, DE	A WATER RESCUE WAS PERFORMED ON WEST ST.
Aug 9, 3:45 PM EDT	FLASH FLOOD	Harrington, DE	EAST LIBERTY ST IS CLOSED BETWEEN DELAWARE AVE AND US-13 DUE TO FLASH FLOODING.

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

The nearest sounding before it

Wallops Is Stn, VA (KWAL), launched 12:00Z, 7.0 hours before the alert went out and 99 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: 927 J/kg
Mixed-layer CIN: -47 J/kg
Mixed-layer LCL: 869 m above ground
0-6 km bulk shear: 8 kt
0-1 km storm-relative helicity: 25 m²/s²
0-3 km storm-relative helicity: 18 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

338 
WGUS51 KPHI 091901
FFWPHI
DEC001-005-092315-
/O.NEW.KPHI.FF.W.0032.210809T1901Z-210809T2315Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Mount Holly NJ
301 PM EDT Mon Aug 9 2021

The National Weather Service in Mount Holly has issued a

* Flash Flood Warning for...
  Southwestern Kent County in central Delaware...
  Central Sussex County in southern Delaware...

* Until 715 PM EDT.

* At 301 PM EDT, Doppler radar and automated rain gauges indicated 
  thunderstorms producing heavy rain across the warned area. Between 
  2 and 2.5 inches of rain have fallen. The expected rainfall rate 
  is 2 to 3 inches in 1 hour. Additional rainfall amounts of 1 to 2 
  inches are possible in the warned area. Flash flooding is ongoing 
  or expected to begin shortly.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Radar and automated gauges.

  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...
  Harrington, Ellendale, Andrewsville, and Farmington.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3891 7571 3898 7562 3889 7550 3878 7535
      3868 7514 3864 7517 3875 7548

FLASH FLOOD...RADAR AND GAUGE INDICATED
EXPECTED RAINFALL...2-3 INCHES IN 1 HOUR

$$

SFJ

2 follow-up statements

650 
WGUS71 KPHI 091944
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
344 PM EDT Mon Aug 9 2021

DEC001-005-092315-
/O.CON.KPHI.FF.W.0032.000000T0000Z-210809T2315Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Kent DE-Sussex DE-
344 PM EDT Mon Aug 9 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 715 PM EDT THIS 
EVENING FOR SOUTHWESTERN KENT AND CENTRAL SUSSEX COUNTIES...

At 344 PM EDT, Doppler radar and automated rain gauges indicated 
thunderstorms producing heavy rain across the warned area. Between 
2.5 and 3.5 inches of rain have fallen. The expected rainfall rate 
is 0.5 to 1 inch in 1 hour. Additional rainfall amounts of 0.5 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 and automated gauges.

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...
  Harrington, Ellendale, Andrewsville, and Farmington.

Although the heaviest rain has ended, additional light rain will 
exacerbate any flooding already occurring. It will take time for 
runoff to recede.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3891 7571 3898 7562 3889 7550 3878 7535
      3868 7514 3864 7517 3875 7548

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

$$

SFJ

202 
WGUS71 KPHI 092117
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
517 PM EDT Mon Aug 9 2021

DEC001-005-092127-
/O.CAN.KPHI.FF.W.0032.000000T0000Z-210809T2315Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Kent DE-Sussex DE-
517 PM EDT Mon Aug 9 2021

...FLASH FLOOD WARNING IS CANCELLED FOR SOUTHWESTERN KENT AND 
CENTRAL SUSSEX COUNTIES...

The heavy rain has ended and flood waters are recededing across the 
warned area. However, another Flash Flood Warning remains in effect 
for portions of Kent County. Please continue to heed remaining road 
closures.

LAT...LON 3891 7571 3898 7562 3889 7550 3878 7535
      3868 7514 3864 7517 3875 7548

$$

Robertson

The office that day

Everything else NWS Philadelphia/Mount Holly issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 9, 2:10 PM EDT	Special Weather Statement	PHI	Sussex	50 min
Aug 9, 2:41 PM EDT	Areal Flood Advisory	PHI	Kent, New Castle, Sussex	3 hr
Aug 9, 3:43 PM EDT	Excessive Heat Watch	PHI	New Castle	12 hr
Aug 9, 4:35 PM EDT	Severe Thunderstorm Warning	PHI	Kent	40 min
Aug 9, 4:36 PM EDT	Areal Flood Advisory	PHI	New Castle	104 min
Aug 9, 4:59 PM EDT	Flash Flood Warning	PHI	Kent	79 min
Aug 9, 5:12 PM EDT	Severe Thunderstorm Warning	PHI	Kent	20 min

Nearby

Flash Flood Warnings in Delaware, 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.