Alert archive / New Jersey / Flash Flood Warnings in 2021

Flash Flood Warning 23, NWS Philadelphia/Mount Holly

July 17, 2021Bucks County, Pennsylvania; Mercer County, Somerset County, New Jersey

NWS Philadelphia/Mount Holly issued this flash flood warning at Jul 17, 2021, 8:09 PM EDT for Bucks County, Pennsylvania; Mercer County, Somerset County, New Jersey. It was in force for 4 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, 8:09 PM EDT (00:09 UTC)
Expired: Jul 18, 2021, 12:00 AM EDT
In force: 4 hr
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Flood severity: None

Counties Mercer County, NJ, Somerset County, NJ, Bucks County, PA

The radar

The Philadelphia radar (KDIX), 49 km from the middle of the area, began a volume at 00:10 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
Jul 17, 8:30 PM EDT	FLASH FLOOD	Ewing, NJ	WIDESPREAD ROADWAY FLOODING WITH SOME ROADS BECOMING IMPASSABLE.
Jul 17, 9:15 PM EDT	FLASH FLOOD	Hopewell, NJ	WIDESPREAD ROADWAY FLOODING WITH SOME ROADS BECOMING IMPASSABLE.
Jul 17, 10:16 PM EDT	FLOOD	1 Nw Eddington, PA	REPORT FROM MPING: STREET/ROAD FLOODING; STREET/ROAD CLOSED; VEHICLES STRANDED.
Jul 17, 11:00 PM EDT	FLASH FLOOD	Bensalem, PA	REPORT OF A WATER RESCUE IN BENSALEM. SPOTTER ALSO REPORTED OVER 3 INCHES OF RAIN. TIME ESTIMATED.
Jul 17, 11:15 PM EDT	FLOOD	Levittown, PA	TRENTON ROAD IN LEVITTOWN IS FLOODED AND ALMOST IMPASSABLE. TIME ESTIMATED.

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, 0.2 hours before the alert went out and 178 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: 1431 J/kg
Mixed-layer CIN: -48 J/kg
Mixed-layer LCL: 988 m above ground
0-6 km bulk shear: 23 kt
0-1 km storm-relative helicity: 26 m²/s²
0-3 km storm-relative helicity: 54 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 1.6

Open this sounding in Storm Lab

The text

As transmitted.

712 
WGUS51 KPHI 180009
FFWPHI
NJC021-035-PAC017-180400-
/O.NEW.KPHI.FF.W.0023.210718T0009Z-210718T0400Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

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

The National Weather Service in Mount Holly has issued a

* Flash Flood Warning for...
  Mercer County in central New Jersey...
  Southwestern Somerset County in northern New Jersey...
  Southeastern Bucks County in southeastern Pennsylvania...

* Until midnight EDT.

* At 809 PM EDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 0.5 and 1.5 inches of 
  rain have already fallen in spots. Additional rainfall amounts of 
  1 to 3 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...
  Trenton, Bensalem, Ewing, Princeton, Bristol, Pennington, Yardley, 
  Newtown, and Hopewell.

This includes the following highways...
	Pennsylvania Turnpike between mile markers 347 and 359.
	Interstate 95 in Pennsylvania between mile markers 34 and 40.
	Interstate 295 in New Jersey between mile markers 58 and 76.
	Interstate 195 in New Jersey between mile markers 0 and 3.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4018 7508 4032 7493 4034 7496 4035 7486
      4038 7487 4038 7480 4042 7481 4043 7475
      4041 7474 4040 7459 4034 7463 4029 7455
      4018 7468 4018 7471 4016 7471 4013 7474
      4013 7482 4008 7486 4005 7497 4012 7496

FLASH FLOOD...RADAR INDICATED

$$

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, 8:44 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, 9:36 PM EDT	Flash Flood Warning	PHI	Delaware, Montgomery, Philadelphia	2 hr
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

Nearby

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