Alert archive / New Jersey / Flash Flood Warnings in 2021

Flash Flood Warning 22, NWS Philadelphia/Mount Holly

July 17, 2021Morris County, Somerset County, New Jersey

NWS Philadelphia/Mount Holly issued this flash flood warning at Jul 17, 2021, 6:15 PM EDT for Morris County, Somerset County, New Jersey. It was in force for 5 hr. 3 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, 6:15 PM EDT (22:15 UTC)
Expired: Jul 17, 2021, 11:29 PM EDT
In force: 5 hr
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Flood severity: None

Counties Morris County, NJ, Somerset County, NJ

The radar

The Philadelphia radar (KDIX), 75 km from the middle of the area, began a volume at 22:19 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, 7:15 PM EDT	FLASH FLOOD	2 Wsw Manville, NJ	US ROUTE 206 IS IMPASSABLE AT CAMPLAIN ROAD IN HILLSBOROUGH TOWNSHIP DUE TO FLOODING.
Jul 17, 10:45 PM EDT	FLASH FLOOD	1 Sw Neshanic Station, NJ	WATER RESCUE REPORTED AT AMWELL ROAD AND BLACKPOINT ROAD. TIME ESTIMATED.
Jul 17, 11:00 PM EDT	FLASH FLOOD	1 E Branchburg Twp, NJ	FLOODING ON THE NORTH BRANCH OF THE RARITAN RIVER AT SOUTH BRANCH BASED ON THE RIVER GAUGE.

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 12:00Z, 10.3 hours before the alert went out and 150 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: 1203 J/kg
Mixed-layer CIN: -55 J/kg
Mixed-layer LCL: 1054 m above ground
0-6 km bulk shear: 24 kt
0-1 km storm-relative helicity: 35 m²/s²
0-3 km storm-relative helicity: 46 m²/s²
Significant tornado parameter: 0.2
Supercell composite: 1.0

Open this sounding in Storm Lab

The text

As transmitted.

806 
WGUS51 KPHI 172215
FFWPHI
NJC027-035-180200-
/O.NEW.KPHI.FF.W.0022.210717T2215Z-210718T0200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

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

The National Weather Service in Mount Holly has issued a

* Flash Flood Warning for...
  Southeastern Morris County in northern New Jersey...
  Somerset County in northern New Jersey...

* Until 1000 PM EDT.

* At 615 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 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...
  Somerville, Somerset, Bridgewater, Madison, Middlesex, Bound 
  Brook, Manville, Chatham, Mendham, Peapack And Gladstone, and Far 
  Hills.

This includes the following highways...
	Interstate 78 in New Jersey between mile markers 27 and 42.
	Interstate 287 in New Jersey between mile markers 11 and 32.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4072 7473 4076 7456 4074 7437 4067 7446
      4066 7445 4066 7440 4062 7443 4057 7452
      4049 7446 4042 7458 4040 7459 4041 7474
      4051 7480 4050 7478 4058 7471 4060 7472
      4062 7470 4063 7473 4067 7473 4070 7472

FLASH FLOOD...RADAR INDICATED

$$

Iovino

2 follow-up statements

430 
WGUS51 KPHI 180110
FFWPHI
NJC027-035-180400-
/O.EXT.KPHI.FF.W.0022.000000T0000Z-210718T0400Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

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

The National Weather Service in Mount Holly has extended the

* Flash Flood Warning for...
  Southeastern Morris County in northern New Jersey...
  Somerset County in northern New Jersey...

* Until midnight EDT.

* At 910 PM EDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 2 and 4 inches of rain 
  have already fallen in spots, especially in western Somerset 
  County. Additional rainfall amounts of 1 to 1.5 inches are 
  possible in the warned area. Flash flooding is ongoing.

  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 additional flash flooding 
  include...
  Somerville, Somerset, Bridgewater, Madison, Middlesex, Bound 
  Brook, Manville, Chatham, Mendham, Peapack And Gladstone, and Far 
  Hills.

This includes the following highways...
	Interstate 78 in New Jersey between mile markers 27 and 42.
	Interstate 287 in New Jersey between mile markers 11 and 32.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4072 7473 4076 7456 4074 7437 4067 7446
      4066 7445 4066 7440 4062 7443 4057 7452
      4049 7446 4042 7458 4040 7459 4041 7474
      4051 7480 4050 7478 4058 7471 4060 7472
      4062 7470 4063 7473 4067 7473 4070 7472

FLASH FLOOD...RADAR INDICATED

$$

Iovino

241 
WGUS71 KPHI 180329
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
1129 PM EDT Sat Jul 17 2021

NJC027-035-180339-
/O.CAN.KPHI.FF.W.0022.000000T0000Z-210718T0400Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Morris NJ-Somerset NJ-
1129 PM EDT Sat Jul 17 2021

...FLASH FLOOD WARNING IS CANCELLED FOR SOUTHEASTERN MORRIS AND 
SOMERSET COUNTIES...

The heavy rain has ended. However, a Flood Warning is now in effect 
for southwestern Somerset County until 9:00 AM Sunday to account for 
runoff from Saturday's heavy rainfall.


LAT...LON 4072 7473 4076 7456 4074 7437 4067 7446
      4066 7445 4066 7440 4062 7443 4057 7452
      4049 7446 4042 7458 4040 7459 4041 7474
      4051 7480 4050 7478 4058 7471 4060 7472
      4062 7470 4063 7473 4067 7473 4070 7472

$$

Iovino

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 17, 12:55 PM EDT	Special Weather Statement	PHI	Hunterdon	50 min
Jul 17, 1:05 PM EDT	Severe Thunderstorm Warning	PHI	Hunterdon, Mercer	40 min
Jul 17, 1:31 PM EDT	Areal Flood Advisory	PHI	Hunterdon	97 min
Jul 17, 1:50 PM EDT	Special Marine Warning	PHI		40 min
Jul 17, 1:56 PM EDT	Severe Thunderstorm Warning	PHI	Hunterdon, Morris, Somerset, Warren	36 min
Jul 17, 2:02 PM EDT	Areal Flood Advisory	PHI	Monmouth, Ocean	92 min
Jul 17, 2:56 PM EDT	Severe Thunderstorm Warning	PHI	Middlesex, Somerset	49 min
Jul 17, 3:06 PM EDT	Severe Thunderstorm Warning	PHI	Warren	39 min
Jul 17, 3:09 PM EDT	Tornado Warning	PHI	Middlesex	21 min
Jul 17, 3:38 PM EDT	Areal Flood Advisory	PHI	Middlesex	40 min
Jul 17, 3:51 PM EDT	Severe Thunderstorm Warning	PHI	Middlesex	24 min
Jul 17, 4:55 PM EDT	Severe Thunderstorm Warning	PHI	Hunterdon, Somerset	50 min
Jul 17, 5:13 PM EDT	Areal Flood Advisory	PHI	Hunterdon	4 hr
Jul 17, 5:19 PM EDT	Tornado Warning	PHI	Hunterdon	14 min
Jul 17, 5:25 PM EDT	Flash Flood Warning	PHI	Hunterdon	6 hr
Jul 17, 5:30 PM EDT	Severe Thunderstorm Warning	PHI	Hunterdon, Warren	19 min
Jul 17, 5:52 PM EDT	Areal Flood Advisory	PHI	Somerset	2 hr
Jul 17, 6:02 PM EDT	Severe Thunderstorm Warning	PHI	Hunterdon, Mercer, Somerset	43 min
Jul 17, 6:39 PM EDT	Severe Thunderstorm Warning	PHI	Hunterdon, Mercer, Middlesex, Morris, Somerset	51 min
Jul 17, 6:51 PM EDT	Severe Thunderstorm Warning	PHI	Burlington	39 min
Jul 17, 6:59 PM EDT	Small Craft Advisory	PHI		7 hr
Jul 17, 7:01 PM EDT	Severe Thunderstorm Warning	PHI	Hunterdon, Somerset	44 min
Jul 17, 7:12 PM EDT	Areal Flood Advisory	PHI	Mercer, Somerset	3 hr
Jul 17, 7:26 PM EDT	Severe Thunderstorm Warning	PHI	Hunterdon, Mercer, Middlesex, Morris, Somerset	49 min

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.