Alert archive / Pennsylvania / Flash Flood Warnings in 2021

Flash Flood Warning 24, NWS Philadelphia/Mount Holly

July 17, 2021Delaware County, Montgomery County, Philadelphia County, Pennsylvania; Camden County, Gloucester County, Salem County, New Jersey; New Castle County, Delaware

NWS Philadelphia/Mount Holly issued this flash flood warning at Jul 17, 2021, 9:36 PM EDT for Delaware County, Montgomery County, Philadelphia County, Pennsylvania; Camden County, Gloucester County, Salem County, New Jersey; New Castle County, Delaware. It was in force for 2 hr. 5 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: Jul 17, 2021, 9:36 PM EDT (01:36 UTC)
Expired: Jul 17, 2021, 11:47 PM EDT
In force: 2 hr
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Flood severity: None

Counties New Castle County, DE, Camden County, NJ, Gloucester County, NJ, Salem County, NJ, Delaware County, PA, Montgomery County, PA, Philadelphia County, PA

The radar

The Philadelphia radar (KDIX), 81 km from the middle of the area, began a volume at 01:38 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
Jul 17, 10:00 PM EDT	FLOOD	Gloucester City, NJ	REPORT OF STREET FLOODING IN THE AREA OF BROADWAY AND MARKET. TIME ESTIMATED.
Jul 17, 10:25 PM EDT	FLASH FLOOD	1 Nnw Holmesburg, PA	FLOODING ALONG THE PENNYPACK CREEK BASED ON THE RIVER GAUGE.
Jul 17, 10:30 PM EDT	FLASH FLOOD	1 Ssw Summerdale, PA	FLOODING ALONG THE FRANKFORD CREEK BASED ON THE RIVER GAUGE.
Jul 17, 10:50 PM EDT	FLOOD	1 Ese Roxborough, PA	REPORT OF FLOODING ON I-76 WESTBOUND BETWEEN CITY AVE AND MONTGOMERY DR.
Jul 17, 11:45 PM EDT	FLOOD	Whitman Park, NJ	FLOODING ON I-676 RAMP NORTHBOUND AT ATLANTIC AVE. ALL LANES CLOSED. TIME ESTIMATED.

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

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 00:00Z, 1.6 hours before the alert went out and 205 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: 933 J/kg
Mixed-layer CIN: -83 J/kg
Mixed-layer LCL: 1286 m above ground
0-6 km bulk shear: 29 kt
0-1 km storm-relative helicity: 163 m²/s²
0-3 km storm-relative helicity: 172 m²/s²
Significant tornado parameter: 0.3
Supercell composite: 1.3

Open this sounding in Storm Lab

The text

As transmitted.

732 
WGUS51 KPHI 180136
FFWPHI
DEC003-NJC007-015-033-PAC045-091-101-180600-
/O.NEW.KPHI.FF.W.0024.210718T0136Z-210718T0600Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Mount Holly NJ
936 PM EDT Sat Jul 17 2021

The National Weather Service in Mount Holly has issued a

* Flash Flood Warning for...
  New Castle County in northern Delaware...
  Northwestern Camden County in southern New Jersey...
  Northwestern Gloucester County in southern New Jersey...
  Northwestern Salem County in southern New Jersey...
  Delaware County in southeastern Pennsylvania...
  Southeastern Montgomery County in southeastern Pennsylvania...
  Philadelphia County in southeastern Pennsylvania...

* Until 200 AM EDT.

* At 936 PM EDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 0.5 and 1 inch of rain 
  has already fallen in spots. 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.

  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 may experience flash flooding include...
  Philadelphia, Camden, Wilmington, Newark, Gloucester City, Cherry 
  Hill, Norristown, Chester, Deptford, Voorhees, West Deptford, and 
  Lindenwold.

This includes the following highways...
	New Jersey Turnpike between exits 1 and 3.
	Pennsylvania Turnpike between mile markers 329 and 346.
	Interstate 95 in Pennsylvania between mile markers 0 and 33.
	Interstate 95 in Delaware between mile markers 0 and 23.
	Interstate 76 in Pennsylvania between mile markers 329 and 351.
	Interstate 76 in New Jersey between mile markers 0 and 3.
	Interstate 295 in New Jersey between mile markers 0 and 35.
	Interstate 676 in Pennsylvania between mile markers 0 and 1.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Motorists should not attempt to drive around barricades or drive 
cars through flooded areas.

&&

LAT...LON 3951 7578 3972 7579 3980 7570 3984 7560
      3987 7560 3994 7552 3999 7544 3999 7545
      4004 7541 4007 7536 4007 7540 4025 7520
      4012 7496 4005 7497 3999 7506 3999 7502
      3995 7501 3994 7498 3985 7492 3952 7553

FLASH FLOOD...RADAR INDICATED

$$

Iovino

1 follow-up statement

154 
WGUS71 KPHI 180347
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
1147 PM EDT Sat Jul 17 2021

DEC003-NJC007-015-033-PAC045-091-101-180357-
/O.CAN.KPHI.FF.W.0024.000000T0000Z-210718T0600Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
New Castle DE-Camden NJ-Gloucester NJ-Salem NJ-Delaware PA-
Montgomery PA-Philadelphia PA-
1147 PM EDT Sat Jul 17 2021

...FLASH FLOOD WARNING IS CANCELLED FOR NEW CASTLE, NORTHWESTERN 
CAMDEN, NORTHWESTERN GLOUCESTER, NORTHWESTERN SALEM, DELAWARE, 
SOUTHEASTERN MONTGOMERY, AND PHILADELPHIA COUNTIES...

The heavy rain has ended. Flooding is no longer expected to pose a 
threat. Please continue to heed remaining road closures.



LAT...LON 3951 7578 3972 7579 3980 7570 3984 7560
      3987 7560 3994 7552 3999 7544 3999 7545
      4004 7541 4007 7536 4007 7540 4025 7520
      4012 7496 4005 7497 3999 7506 3999 7502
      3995 7501 3994 7498 3985 7492 3952 7553

$$

Iovino

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 17, 8:00 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Montgomery, Philadelphia	45 min
Jul 17, 8:09 PM EDT	Flash Flood Warning	PHI	Bucks	4 hr
Jul 17, 8:44 PM EDT	Areal Flood Advisory	PHI	Chester, Montgomery	82 min
Jul 17, 8:57 PM EDT	Severe Thunderstorm Warning	PHI	Chester	48 min
Jul 17, 9:15 PM EDT	Areal Flood Advisory	PHI	Delaware, Montgomery, Philadelphia	2 hr
Jul 17, 9:27 PM EDT	Severe Thunderstorm Warning	PHI	Chester, Delaware, Montgomery, Philadelphia	48 min
Jul 17, 9:48 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Delaware, Montgomery, Philadelphia	42 min
Jul 17, 10:21 PM EDT	Severe Thunderstorm Warning	PHI	Bucks	54 min
Jul 17, 8:35 PM EDT	Severe Thunderstorm Warning	PHI	Atlantic, Burlington, Camden, Gloucester	40 min
Jul 17, 8:36 PM EDT	Severe Thunderstorm Warning	PHI	Burlington, Mercer, Middlesex, Monmouth, Ocean, Somerset	54 min
Jul 17, 8:46 PM EDT	Special Marine Warning	PHI		59 min
Jul 17, 8:53 PM EDT	Areal Flood Advisory	PHI	Mercer, Middlesex, Monmouth	3 hr
Jul 17, 9:25 PM EDT	Areal Flood Advisory	PHI	Burlington, Camden, Gloucester, Salem	2 hr
Jul 17, 9:30 PM EDT	Severe Thunderstorm Warning	PHI	Cape May	29 min
Jul 17, 9:44 PM EDT	Special Marine Warning	PHI		61 min
Jul 17, 10:22 PM EDT	Tornado Warning	PHI	Burlington, Monmouth, Ocean	23 min
Jul 17, 10:27 PM EDT	Special Weather Statement	PHI	Burlington, Camden	33 min
Jul 17, 10:38 PM EDT	Tornado Warning	PHI	Burlington, Monmouth, Ocean	16 min
Jul 17, 10:43 PM EDT	Flash Flood Warning	PHI	Burlington, Mercer, Middlesex, Monmouth, Ocean	79 min
Jul 17, 10:47 PM EDT	Special Marine Warning	PHI		118 min
Jul 17, 10:51 PM EDT	Special Marine Warning	PHI		114 min
Jul 17, 11:07 PM EDT	Special Weather Statement	PHI	Middlesex	38 min
Jul 17, 11:08 PM EDT	Areal Flood Warning	PHI	Hunterdon	12 hr
Jul 17, 11:11 PM EDT	Special Weather Statement	PHI	Monmouth, Ocean	34 min
Jul 17, 11:20 PM EDT	Special Marine Warning	PHI		115 min
Jul 17, 11:26 PM EDT	Areal Flood Warning	PHI	Somerset	10 hr
Jul 18, 2:41 AM EDT	Areal Flood Warning	PHI	Mercer	4 hr
Jul 18, 3:48 AM EDT	River Flood Warning	PHI	Mercer	3 hr
Jul 18, 9:08 AM EDT	Areal Flood Warning	PHI	Somerset	2 hr
Jul 18, 11:03 AM EDT	River Flood Warning	PHI	Middlesex, Somerset	88 min
Jul 17, 8:40 PM EDT	Special Weather Statement	PHI	Kent	35 min
Jul 17, 10:36 PM EDT	Special Weather Statement	PHI	Kent	24 min
Jul 17, 10:54 PM EDT	Areal Flood Advisory	PHI	Kent	48 min
Jul 17, 10:55 PM EDT	Severe Thunderstorm Warning	PHI	Kent	50 min

Nearby

Flash Flood Warnings in Pennsylvania, 2021 Flash Flood Warnings in New Jersey, 2021 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.