Alert archive / Delaware / Flash Flood Warnings in 2020

Flash Flood Warning 37, NWS Philadelphia/Mount Holly

August 4, 2020New Castle County, Delaware; Cecil County, Maryland

NWS Philadelphia/Mount Holly issued this flash flood warning at Aug 4, 2020, 9:23 AM EDT for New Castle County, Delaware; Cecil County, Maryland. It was in force for 4 hr. 23 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 4, 2020, 9:23 AM EDT (13:23 UTC)
Expired: Aug 4, 2020, 1:15 PM EDT
In force: 4 hr
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Flood severity: None

Counties New Castle County, DE, Cecil County, MD

The radar

The Dover AFB radar (KDOX), 84 km from the middle of the area, began a volume at 13:25 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.

What was reported inside it

Time	Report	Where	Remark
Aug 4, 9:26 AM EDT	HEAVY RAIN 2.64	1 Nw Odessa, DE	MESONET STATION CW5801 MIDDLETOWN.
Aug 4, 9:45 AM EDT	FLASH FLOOD	2 S Brookside, DE	CORRECTS PREVIOUS FLASH FLOOD REPORT FROM 2 S BROOKSIDE. THE GAUGE ON THE CHRISTINA RIVER AT COOCHS BRIDGE REACHED FLOOD STAGE AT 945 AM AND CRESTED AT 13.98 FEET (MAJOR FLOODING) AT 332 PM ON AUGUST 4.
Aug 4, 9:45 AM EDT	FLASH FLOOD	2 S Brookside, DE	THE GAUGE ON THE CHRISTINA RIVER AT COOCHS BRIDGE REACHED FLOOD STAGE AT 945 AM AND CRESTED AT 13.98 FEET AT 732 PM ON AUGUST 4.
Aug 4, 10:26 AM EDT	FLASH FLOOD	2 W Elkton, MD	FLASH FLOODING CLOSED U.S. HIGHWAY 40 NEAR THIOKOL ROAD. TIME BASED ON DISPATCH REPORT.
Aug 4, 10:35 AM EDT	FLASH FLOOD	Elkton, MD	STATE HIGHWAY 7 CLOSED AT HOWARD STREET FROM A COMBINATION OF COASTAL FLOODING AND FLASH FLOODING. TIME BASED ON DISPATCH REPORT.
Aug 4, 10:45 AM EDT	FLASH FLOOD	1 W Barksdale, MD	GAUGE ON BIG ELK CREEK AT ELK MILLS CRESTED AT 12.88 FT, CORRESPONDING TO MAJOR FLOOD STAGE.
Aug 4, 10:45 AM EDT	HEAVY RAIN 4.33	2 Nnw Nottingham Manor, DE	MESONET STATION EW9357 NEWARK.
Aug 4, 10:45 AM EDT	HEAVY RAIN 5.02	4 W Brantwood, MD	MESONET STATION AR187 ELKTON.
Aug 4, 10:53 AM EDT	HEAVY RAIN 6.41	1 W Appleton, MD	MESONET STATION FW1370 KEMBLESVILLE.
Aug 4, 11:00 AM EDT	FLASH FLOOD	1 Sse Eastburn Heights, DE	THE GAUGE ON THE WHITE CLAY CREEK AT NEWARK REACHED FLOOD STAGE AT 1100 AM AND CRESTED AT 16.49 FEET (0.01 FT SHY OF MAJOR FLOOD STAGE) AT 745 PM ON AUGUST 4.
Aug 4, 11:20 AM EDT	FLASH FLOOD	1 W North East, MD	FLOODING CLOSED STATE HIGHWAY 7 AT WELLS CAMP ROAD. TIME BASED ON DISPATCH REPORT.
Aug 4, 11:22 AM EDT	FLASH FLOOD	1 Sw Chesapeake City, MD	FLOODING CLOSED STATE HIGHWAY 213 AT BASIL AVENUE. TIME BASED ON DISPATCH REPORT.
Aug 4, 11:41 AM EDT	FLASH FLOOD	North East, MD	STATE HIGHWAY 272 SOUTHBOUND AT RONEY AVENUE CLOSED FROM FLOODING. TIME BASED ON DISPATCH REPORT.
Aug 4, 11:54 AM EDT	COASTAL FLOOD	2 Se Delaware City, DE	TIDAL GAUGE ON THE DELAWARE BAY AT REEDY POINT CRESTED IN MINOR FLOOD STAGE AT 7.81 FT THIS AFTERNOON.
Aug 4, 12:00 PM EDT	HEAVY RAIN 4.14	2 Nnw Nottingham Manor, DE	COCORAHS STATION DE-NC-34 NEWARK 2.3 NNW.
Aug 4, 12:00 PM EDT	HEAVY RAIN 4.54	Brookside, DE	CO-OP OBSERVER STATION NEWD1 BROOKSIDE.
Aug 4, 12:15 PM EDT	HEAVY RAIN 3.57	1 N Woodshade, DE	MESONET STATION FW2774 NEWARK.
Aug 4, 12:34 PM EDT	HEAVY RAIN 5.43	2 Se Pleasant Hill, MD	MESONET STATION EW3643 ELKTON.
Aug 4, 12:35 PM EDT	HEAVY RAIN 5.71	West Nottingham, MD	MESONET STATION DW3118 COLORA.
Aug 4, 12:36 PM EDT	HEAVY RAIN 4.47	1 Ne Midvale, DE	ASOS STATION KILG WILMINGTON.
Aug 4, 12:40 PM EDT	HEAVY RAIN 4.06	3 W Mount Pleasant, DE	MESONET STATION FW7093 MIDDLETOWN.
Aug 4, 12:44 PM EDT	HEAVY RAIN 4.33	1 Sw Brookside, DE	MESONET STATION FW2897 NEWARK.
Aug 4, 12:50 PM EDT	HEAVY RAIN 4.11	2 Ene Glasgow, DE	MESONET STATION AR962 NEWARK.

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, 1.4 hours before the alert went out and 183 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: 472 J/kg
Mixed-layer CIN: -6 J/kg
Mixed-layer LCL: 648 m above ground
0-6 km bulk shear: 52 kt
0-1 km storm-relative helicity: 254 m²/s²
0-3 km storm-relative helicity: 273 m²/s²
Significant tornado parameter: 0.8
Supercell composite: 2.9

Open this sounding in Storm Lab

The text

As transmitted.

589 
WGUS51 KPHI 041323
FFWPHI
DEC003-MDC015-041715-
/O.NEW.KPHI.FF.W.0037.200804T1323Z-200804T1715Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Mount Holly NJ
923 AM EDT Tue Aug 4 2020

The National Weather Service in Mount Holly NJ has issued a

* Flash Flood Warning for...
  New Castle County in northern Delaware...
  Cecil County in northeastern Maryland...

* Until 115 PM EDT.

* At 922 AM EDT, Doppler radar indicated thunderstorms producing 
  heavy rain just south of the warned area. Up to two inches of rain 
  have already fallen across portions of Kent Counties in both 
  Maryland and Delaware, as well as southern Cecil County. The heavy 
  rain was moving north and will move into the warned area shortly. 
  Flash flooding will likely occur as a result.

  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 could experience flooding include...
  Wilmington, Newark, Middletown, Elkton, Calvert, Pennsville,
  Carneys Point, New Castle, Salem, North East, Rising Sun, Delaware
  City, Charlestown, Newport, Blake, Stanton, Glasgow, Bohemias
  Mills, West Nottingham and Bay View.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Protecting yourself from immediate threats to life and safety shall
take priority.  Whenever possible, as long as it does not cause
greater harm, all COVID-19 protective action guidance should be
followed.

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

A Flash Flood Warning means that flooding is imminent or occurring.
If you are in the warned area move to higher ground immediately.
Residents living along streams and creeks should take immediate
precautions to protect life and property.

&&

LAT...LON 3972 7623 3972 7548 3963 7556 3960 7556
      3960 7552 3959 7554 3957 7551 3966 7548
      3965 7548 3960 7546 3954 7554 3950 7553
      3951 7548 3946 7554 3943 7545 3942 7546
      3936 7543 3949 7588 3960 7613

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

$$

Kruzdlo

1 follow-up statement

562 
WGUS71 KPHI 041713
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
113 PM EDT Tue Aug 4 2020

DEC003-MDC015-041723-
/O.EXP.KPHI.FF.W.0037.000000T0000Z-200804T1715Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
New Castle DE-Cecil MD-
113 PM EDT Tue Aug 4 2020

...THE FLASH FLOOD WARNING FOR NEW CASTLE AND CECIL COUNTIES WILL
EXPIRE AT 115 PM EDT...

The heavy rain has ended. Water is receding. Please continue to heed 
any remaining road closures.

LAT...LON 3972 7623 3972 7548 3963 7556 3960 7556
      3960 7552 3959 7554 3957 7551 3966 7548
      3965 7548 3960 7546 3954 7554 3950 7553
      3951 7548 3946 7554 3943 7545 3942 7546
      3936 7543 3949 7588 3960 7613

$$

Kruzdlo

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 4, 4:50 AM EDT	Tornado Warning	PHI	Sussex	25 min
Aug 4, 5:17 AM EDT	Areal Flood Advisory	PHI	New Castle	4 hr
Aug 4, 7:28 AM EDT	Flash Flood Warning	PHI	New Castle	3 hr
Aug 4, 7:39 AM EDT	Tornado Warning	PHI	Sussex	36 min
Aug 4, 7:51 AM EDT	Tornado Warning	PHI	Sussex	24 min
Aug 4, 8:15 AM EDT	Tornado Warning	PHI	Kent	45 min
Aug 4, 8:18 AM EDT	Tornado Warning	PHI	Sussex	27 min
Aug 4, 8:27 AM EDT	Tornado Warning	PHI	Kent	33 min
Aug 4, 8:56 AM EDT	Tornado Warning	PHI	Kent, New Castle	34 min
Aug 4, 8:58 AM EDT	Flash Flood Warning	PHI	Kent, New Castle, Sussex	3 hr
Aug 4, 9:06 AM EDT	River Flood Warning	PHI	New Castle	11 hr
Aug 4, 9:23 AM EDT	Tornado Warning Tornado observed	PHI	New Castle	22 min
Aug 4, 10:02 AM EDT	Flash Flood Warning	PHI	New Castle	4 hr
Aug 4, 10:38 AM EDT	River Flood Warning	PHI	New Castle	14 hr
Aug 4, 12:27 PM EDT	River Flood Warning	PHI	New Castle	10 hr
Aug 4, 12:48 PM EDT	River Flood Warning	PHI	New Castle	24 hr
Aug 4, 1:59 PM EDT	Areal Flood Warning	PHI	New Castle	9 hr
Aug 4, 1:33 AM EDT	Areal Flood Advisory	PHI	Caroline, Kent, Queen Anne's, Talbot	4 hr
Aug 4, 2:10 AM EDT	Flash Flood Warning	PHI	Caroline, Kent, Queen Anne's, Talbot	4 hr
Aug 4, 6:55 AM EDT	Tornado Warning	PHI	Kent, Queen Anne's	35 min
Aug 4, 7:22 AM EDT	Tornado Warning	PHI	Kent, Queen Anne's	23 min
Aug 4, 7:50 AM EDT	Flash Flood Warning	PHI	Caroline, Kent, Queen Anne's, Talbot	4 hr
Aug 4, 8:13 AM EDT	Tornado Warning	PHI	Kent, Queen Anne's, Talbot	26 min
Aug 4, 8:50 AM EDT	Flash Flood Warning	PHI	Caroline, Cecil, Kent, Queen Anne's	4 hr

Nearby

Flash Flood Warnings in Delaware, 2020 Flash Flood Warnings in Maryland, 2020 Every flash flood warning in 2020

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.