Alert archive / New Jersey / Flash Flood Warnings in 2021

Flash Flood Warning 51, NWS Philadelphia/Mount Holly

August 22, 20215 counties in New Jersey

NWS Philadelphia/Mount Holly issued this flash flood warning at Aug 22, 2021, 3:10 AM EDT for 5 counties in New Jersey. It was in force for 8 hr. 26 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 22, 2021, 3:10 AM EDT (07:10 UTC)
Expired: Aug 22, 2021, 10:52 AM EDT
In force: 8 hr
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Flood severity: None

Counties Burlington County, NJ, Hunterdon County, NJ, Mercer County, NJ, Monmouth County, NJ, Ocean County, NJ

The radar

The Philadelphia radar (KDIX), 44 km from the middle of the area, began a volume at 07:10 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 22, 5:15 AM EDT	FLASH FLOOD	1 Ne Mercerville, NJ	WATER RESCUE ON PAXSON AVENUE IN HAMILTON TOWNSHIP. TIME ESTIMATED.
Aug 22, 5:40 AM EDT	FLASH FLOOD	1 Wnw East Windsor Twp, NJ	FLOODING AND ROAD CLOSURES IN THE LOCUST CORNER AREA. TIME BASED ON DISPATCH REPORT.
Aug 22, 6:15 AM EDT	FLASH FLOOD	1 Nne Windsor, NJ	FLOODING IN THE HANKINS ROAD AND WOODLAND DRIVE AREAS. WATER RESCUES IN PROGRESS. TIME BASED ON DISPATCH REPORTS.
Aug 22, 6:25 AM EDT	FLASH FLOOD	1 S East Windsor Twp, NJ	WATER RESCUE NEAR THE INTERSECTION OF MERCER STREET AND AIRPORT ROAD. TIME BASED ON DISPATCH REPORT.
Aug 22, 6:27 AM EDT	FLASH FLOOD	East Windsor Twp, NJ	U.S. HIGHWAY 130 CLOSED SOUTH OF PRINCETON-HIGHTSTOWN ROAD FROM FLOODING. TIME BASED ON DISPATCH REPORT.
Aug 22, 6:50 AM EDT	FLASH FLOOD	1 Nnw East Windsor Twp, NJ	WATER RESCUE ON OLD TRENTON ROAD. TIME BASED ON DISPATCH REPORT.
Aug 22, 7:00 AM EDT	FLASH FLOOD	1 Sse Princeton, NJ	THE MILLSTONE RIVER WAS FLOODING, CAUSING INUNDATION OF SEVERAL ROADS TRAVERSING IT IN WEST WINDSOR TWP. TIME ESTIMATED BASED ON NEARBY DISPATCH REPORTS AND SOCIAL MEDIA POSTS.
Aug 22, 7:00 AM EDT	HEAVY RAIN 5.12	2 Wsw East Windsor Twp, NJ	CO-OP OBSERVER STATION HGTN4 1.9 NE WINDSOR.
Aug 22, 7:08 AM EDT	HEAVY RAIN 5.12	1 Wsw East Windsor Twp, NJ
Aug 22, 7:15 AM EDT	FLASH FLOOD	Trenton, NJ	FLOODING AND WATER RESCUES NEAR BROAD STREET AND MERCER STREET. TIME BASED ON DISPATCH REPORT.
Aug 22, 7:30 AM EDT	FLASH FLOOD	Windsor, NJ	U.S. HIGHWAY 130 CLOSED AT CHURCH ROAD FROM FLOODING. TIME BASED ON DISPATCH REPORTS.
Aug 22, 7:30 AM EDT	HEAVY RAIN 2.45	1 Wnw Lawrenceville, NJ	COCORAHS STATION NJ-MC-30 HOPEWELL TWP 3.9 SE.
Aug 22, 7:40 AM EDT	HEAVY RAIN 1.75	0.25 S Trenton Mercer A, NJ	.
Aug 22, 7:40 AM EDT	HEAVY RAIN 1.75	0.25 S Trenton Mercer A, NJ
Aug 22, 7:45 AM EDT	HEAVY RAIN 1.54	1 Nne Ewing, NJ	COCORAHS STATION NJ-MC-29 EWING TWP.
Aug 22, 7:46 AM EDT	FLASH FLOOD	Hightstown, NJ	FLOODING ON STATE HIGHWAY 33 EAST OF MAIN STREET WITH THE ROAD CLOSED.
Aug 22, 8:33 AM EDT	HEAVY RAIN 4.24	1 Nw Princeton Junction, NJ	COCORAHS STATION NJ-MC-56 WEST WINDSOR TWP 2.6 N.
Aug 22, 8:45 AM EDT	HEAVY RAIN 6.69	1 Wsw Hopewell, NJ	COCORAHS STATION NJ-MC-46 HOPEWELL.
Aug 22, 8:49 AM EDT	HEAVY RAIN 4.14	Hamilton Square, NJ
Aug 22, 9:00 AM EDT	HEAVY RAIN 3.15	4 Se Clarksburg, NJ	COCORAHS STATION NJ-OC-33 JACKSON TWP 4.1 NNW.
Aug 22, 9:10 AM EDT	HEAVY RAIN 1.98	1 Nne Burlington Twp, NJ	COCORAHS STATION NJ-BT-3 BURLINGTON 1.7 E.
Aug 22, 9:13 AM EDT	HEAVY RAIN 4.59	4 Nw Pennington, NJ	COCORAHS STATION NJ-MC-27 HOPEWELL TWP. 2.4 NW.
Aug 22, 9:22 AM EDT	FLASH FLOOD	1 Se Princeton Junction, NJ	GROVERS MILL POND HAD FLOODED SEVERAL ROADS SURROUNDING. NEIGHBORING BUILDINGS ALSO HAD WATER DAMAGE. TIME BASED ON SOCIAL MEDIA POST.
Aug 22, 10:10 AM EDT	HEAVY RAIN 3.92	Lawrenceville, NJ
Aug 22, 10:38 AM EDT	HEAVY RAIN 2.75	Mercerville, NJ
Aug 22, 11:00 AM EDT	HEAVY RAIN 1.35	Washington Crossing, PA	MESONET STATION WASN4 WASHINGTON CROSSING.

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

The nearest sounding before it

Brookhaven, NY (KOKX), launched 00:00Z, 7.2 hours before the alert went out and 169 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: 1163 J/kg
Mixed-layer CIN: -6 J/kg
Mixed-layer LCL: 543 m above ground
0-6 km bulk shear: 21 kt
0-1 km storm-relative helicity: 75 m²/s²
0-3 km storm-relative helicity: 85 m²/s²
Significant tornado parameter: 0.3
Supercell composite: 1.7

Open this sounding in Storm Lab

The text

As transmitted.

504 
WGUS51 KPHI 220710
FFWPHI
NJC005-019-021-025-029-221200-
/O.NEW.KPHI.FF.W.0051.210822T0710Z-210822T1200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Mount Holly NJ
310 AM EDT Sun Aug 22 2021

The National Weather Service in Mount Holly has issued a

* Flash Flood Warning for...
  Mercer County in central New Jersey...
  Southwestern Monmouth County in central New Jersey...
  Southeastern Hunterdon County in northwestern New Jersey...
  North Central Burlington County in southern New Jersey...
  Northwestern Ocean County in southern New Jersey...

* Until 800 AM EDT.

* At 310 AM EDT, Doppler radar indicated heavy rain across the 
  warned area. Between 0.5 and 1 inch of rain has already fallen in 
  spots. Additional rainfall amounts of 2 to 3 inches are possible 
  in the warned area. Flash flooding is ongoing or expected to begin 
  shortly.

  HAZARD...Flash flooding caused by heavy rain.

  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 will experience flash flooding include...
  Trenton, Ewing, Princeton, Florence, Burlington, Bristol, 
  Hightstown, Bordentown, Pennington, Hopewell and Allentown.

This includes the following highways...
	New Jersey Turnpike between exits 6 and 8A.
	Interstate 295 in New Jersey between mile markers 49 and 76.
	Interstate 195 in New Jersey between mile markers 0 and 24.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4034 7494 4047 7492 4043 7480 4043 7475
      4038 7472 4039 7465 4038 7462 4032 7462
      4027 7448 4025 7448 4024 7425 4011 7430
      4001 7480 4010 7484 4013 7482 4012 7478
      4016 7472 4022 7477 4025 7484 4030 7487

FLASH FLOOD...RADAR INDICATED

$$

Iovino

4 follow-up statements

794 
WGUS71 KPHI 221110
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
710 AM EDT Sun Aug 22 2021

NJC005-029-221120-
/O.CAN.KPHI.FF.W.0051.000000T0000Z-210822T1200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Burlington NJ-Ocean NJ-
710 AM EDT Sun Aug 22 2021

...FLASH FLOOD WARNING IS CANCELLED FOR NORTH CENTRAL BURLINGTON AND 
NORTHWESTERN OCEAN COUNTIES...

Flooding is no longer expected to pose a threat. Please continue to 
heed remaining road closures.

A Flood Watch remains in effect until 800 AM Monday.

LAT...LON 4034 7494 4047 7492 4043 7475 4038 7472
      4039 7465 4038 7462 4032 7462 4027 7448
      4025 7448 4024 7425 4017 7428 4017 7441
      4008 7455 4014 7459 4018 7471 4015 7472
      4022 7477 4025 7484 4030 7487

$$

NJC019-021-025-221200-
/O.CON.KPHI.FF.W.0051.000000T0000Z-210822T1200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Hunterdon NJ-Mercer NJ-Monmouth NJ-
710 AM EDT Sun Aug 22 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 8 AM EDT THIS MORNING 
FOR MERCER, SOUTHWESTERN MONMOUTH, AND SOUTHEASTERN HUNTERDON 
COUNTIES...

At 710 AM EDT, Doppler radar indicated heavy rain across the warned 
area. Between 3 and 7 inches of rain have fallen. 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 heavy rain.

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 will experience flash flooding include...
  Trenton, Ewing, Princeton, Hightstown, Pennington, Hopewell, 
  Allentown, Roosevelt, Edinburg, Mercerville-Hamilton Square, 
  Windsor, and Lawrenceville.

This includes the following highways...
	New Jersey Turnpike between exits 8 and 8A.
	Interstate 295 in New Jersey between mile markers 58 and 76.
	Interstate 195 in New Jersey between mile markers 0 and 16.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4034 7494 4047 7492 4043 7475 4038 7472
      4039 7465 4038 7462 4032 7462 4027 7448
      4025 7448 4024 7425 4017 7428 4017 7441
      4008 7455 4014 7459 4018 7471 4015 7472
      4022 7477 4025 7484 4030 7487

FLASH FLOOD...RADAR INDICATED

$$

Iovino

037 
WGUS51 KPHI 221112
FFWPHI
NJC019-021-025-221500-
/O.EXT.KPHI.FF.W.0051.000000T0000Z-210822T1500Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Mount Holly NJ
712 AM EDT Sun Aug 22 2021

The National Weather Service in Mount Holly has extended the

* Flash Flood Warning for...
  Mercer County in central New Jersey...
  Southwestern Monmouth County in central New Jersey...
  Southeastern Hunterdon County in northwestern New Jersey...

* Until 1100 AM EDT.

* At 712 AM EDT, Doppler radar indicated heavy rain across the 
  warned area. Between 3 and 7 inches of rain have fallen. 
  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 heavy rain.

  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 will experience flash flooding include...
  Trenton, Ewing, Princeton, Hightstown, Pennington, Hopewell, 
  Allentown, Roosevelt, Edinburg, Mercerville-Hamilton Square, 
  Windsor, and Lawrenceville.

This includes the following highways...
	New Jersey Turnpike between exits 8 and 8A.
	Interstate 295 in New Jersey between mile markers 59 and 76.
	Interstate 195 in New Jersey between mile markers 0 and 16.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4034 7494 4047 7492 4043 7475 4038 7472
      4039 7465 4038 7462 4032 7462 4027 7448
      4025 7448 4024 7425 4017 7428 4017 7441
      4008 7455 4014 7459 4018 7471 4015 7472
      4022 7477 4025 7484 4030 7487

FLASH FLOOD...RADAR INDICATED

$$

Iovino

522 
WGUS71 KPHI 221200
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
800 AM EDT Sun Aug 22 2021

NJC019-021-025-221500-
/O.CON.KPHI.FF.W.0051.000000T0000Z-210822T1500Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Hunterdon NJ-Mercer NJ-Monmouth NJ-
800 AM EDT Sun Aug 22 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 11 AM EDT THIS 
MORNING FOR MERCER, SOUTHWESTERN MONMOUTH, AND SOUTHEASTERN 
HUNTERDON COUNTIES...

At 800 AM EDT, local law enforcement reported flash flooding across 
the warned area. Several roads are closed in Mercer County with 
water rescues reported in Trenton, Hamilton, and East Windsor. 
Between 3 and 7 inches of rain have fallen. Additional rainfall 
amounts of 0.5 to 1 inch are possible in the warned area.

HAZARD...Flash flooding caused by heavy rain.

SOURCE...Law enforcement reported.

IMPACT...Flooding of small creeks and streams, urban areas,
         highways, streets, and underpasses as well as other
         drainage and low lying areas.

For Assunpink Creek at Trenton:
At 7:15am the stage was 7.13 feet.
Flood Stage is 8.5 feet.

This includes the following highways...
	New Jersey Turnpike between exits 8 and 8A.
	Interstate 295 in New Jersey between mile markers 59 and 76.
	Interstate 195 in New Jersey between mile markers 0 and 16.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4034 7494 4047 7492 4043 7475 4038 7472
      4039 7465 4038 7462 4032 7462 4027 7448
      4025 7448 4024 7425 4017 7428 4017 7441
      4008 7455 4014 7459 4018 7471 4015 7472
      4022 7477 4025 7484 4030 7487

FLASH FLOOD...OBSERVED

$$

CMS

654 
WGUS71 KPHI 221452
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
1052 AM EDT Sun Aug 22 2021

NJC019-021-025-221502-
/O.CAN.KPHI.FF.W.0051.000000T0000Z-210822T1500Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Hunterdon NJ-Mercer NJ-Monmouth NJ-
1052 AM EDT Sun Aug 22 2021

...FLASH FLOOD WARNING FOR MERCER, SOUTHWESTERN MONMOUTH, AND 
SOUTHEASTERN HUNTERDON COUNTIES HAS BEEN REPLACED WITH A FLOOD 
WARNING...

Please continue to heed road closures.

LAT...LON 4034 7494 4047 7492 4043 7475 4038 7472
      4039 7465 4038 7462 4032 7462 4027 7448
      4025 7448 4024 7425 4017 7428 4017 7441
      4008 7455 4014 7459 4018 7471 4015 7472
      4022 7477 4025 7484 4030 7487

$$

CMS

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 21, 9:35 PM EDT	Areal Flood Advisory	PHI	Mercer, Middlesex, Monmouth, Ocean	3 hr
Aug 21, 10:47 PM EDT	Areal Flood Advisory	PHI	Morris	3 hr
Aug 21, 11:38 PM EDT	Areal Flood Advisory	PHI	Atlantic, Burlington, Monmouth, Ocean	3 hr
Aug 22, 12:04 AM EDT	Areal Flood Advisory	PHI	Atlantic, Burlington, Camden, Monmouth, Ocean	3 hr
Aug 22, 12:24 AM EDT	Flash Flood Warning	PHI	Morris	3 hr
Aug 22, 1:30 AM EDT	Areal Flood Advisory	PHI	Middlesex, Monmouth	4 hr
Aug 22, 1:35 AM EDT	Areal Flood Advisory	PHI	Morris, Somerset	3 hr
Aug 22, 2:04 AM EDT	Flash Flood Warning	PHI	Middlesex, Monmouth	9 hr
Aug 22, 2:09 AM EDT	Flash Flood Warning	PHI	Burlington, Ocean	5 hr
Aug 22, 2:40 AM EDT	Flash Flood Warning	PHI	Hunterdon, Morris, Somerset	5 hr
Aug 22, 4:21 AM EDT	Flash Flood Warning	PHI	Monmouth, Ocean	3 hr
Aug 22, 5:36 AM EDT	Flash Flood Warning Considerable damage threat	PHI	Mercer, Middlesex, Monmouth, Somerset	5 hr
Aug 22, 6:07 AM EDT	Flash Flood Warning	PHI	Hunterdon, Warren	67 min
Aug 22, 7:52 AM EDT	Areal Flood Warning	PHI	Hunterdon, Somerset	15 hr
Aug 22, 10:43 AM EDT	Special Marine Warning	PHI		62 min
Aug 22, 10:49 AM EDT	Areal Flood Warning	PHI	Middlesex, Monmouth, Somerset	13 hr
Aug 22, 10:52 AM EDT	Areal Flood Warning	PHI	Hunterdon, Mercer, Monmouth	13 hr
Aug 22, 11:06 AM EDT	Special Marine Warning	PHI		54 min
Aug 22, 1:35 PM EDT	Coastal Flood Advisory	PHI	Cape May	10 hr
Aug 22, 1:53 PM EDT	Areal Flood Advisory	PHI	Morris	6 hr
Aug 22, 3:21 PM EDT	River Flood Warning	PHI	Somerset	54 hr
Aug 22, 5:07 PM EDT	Areal Flood Advisory	PHI	Morris, Sussex, Warren	6 hr
Aug 22, 5:48 PM EDT	Flash Flood Warning	PHI	Morris, Sussex, Warren	6 hr

Nearby

Flash Flood Warnings in New Jersey, 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.