Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 197, NWS Philadelphia/Mount Holly

July 17, 2021New Castle County, Delaware; 4 counties in Pennsylvania; Gloucester County, Salem County, New Jersey

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Jul 17, 2021, 9:27 PM EDT for New Castle County, Delaware; 4 counties in Pennsylvania; Gloucester County, Salem County, New Jersey. It was in force for 48 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued: Jul 17, 2021, 9:27 PM EDT (01:27 UTC)
Expired: Jul 17, 2021, 10:15 PM EDT
In force: 48 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Hail: 1.0 in
Wind: 60.0 mph

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

The radar

The Philadelphia radar (KDIX), 79 km from the middle of the area, began a volume at 01:26 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.

The watch it was issued in

The SPC watch in force over the same counties when this warning went out.

Issued	Product	Office	Lasted
Jul 17, 1:13 PM EDT	Severe Thunderstorm Watch	SPC	10 hr

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 00:00Z, 1.5 hours before the alert went out and 207 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.

941 
WUUS51 KPHI 180127
SVRPHI
DEC003-NJC015-033-PAC029-045-091-101-180215-
/O.NEW.KPHI.SV.W.0197.210718T0127Z-210718T0215Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Mount Holly NJ
927 PM EDT Sat Jul 17 2021

The National Weather Service in Mount Holly NJ has issued a

* Severe Thunderstorm Warning for...
  Northern New Castle County in northern Delaware...
  Northwestern Salem County in southern New Jersey...
  Northwestern Gloucester County in southern New Jersey...
  Southeastern Montgomery County in southeastern Pennsylvania...
  Southeastern Chester County in southeastern Pennsylvania...
  Philadelphia County in southeastern Pennsylvania...
  Delaware County in southeastern Pennsylvania...

* Until 1015 PM EDT.

* At 927 PM EDT, severe thunderstorms were located along a line
  extending from Newtown Square to New Castle, moving northeast at 30
  mph.

  HAZARD...60 mph wind gusts and quarter size hail.

  SOURCE...Radar indicated.

  IMPACT...Minor damage to vehicles is possible. Wind damage to 
           roofs, siding, trees, and power lines is possible.

* Locations impacted include...
  Philadelphia, Camden, Wilmington, Newark, West Chester, Chester,
  West Deptford, Pennsville, Yeadon, Westtown, Carneys Point,
  Conshohocken, Hatboro, Folcroft, Swarthmore, Elsmere, Paulsboro,
  New Castle, Penns Grove and Salem.

This includes the following highways...
 New Jersey Turnpike between exits 1 and 2.
 Pennsylvania Turnpike between mile markers 333 and 346.
 Interstate 95 in Pennsylvania between mile markers 0 and 17, and
between mile markers 19 and 23.
 Interstate 95 in Delaware between mile markers 3 and 23.
 Interstate 76 in Pennsylvania between mile markers 330 and 350.
 Interstate 295 in New Jersey between mile markers 0 and 21.
 Interstate 676 in Pennsylvania between mile markers 0 and 1.
 Interstate 476 in Pennsylvania between mile markers 0 and 19.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

Torrential rainfall is occurring with these storms, and may lead to
flash flooding. Do not drive your vehicle through flooded roadways.

&&

LAT...LON 3994 7564 4020 7511 4019 7510 4014 7503
      3996 7512 3995 7514 3993 7514 3959 7531
      3955 7569 3967 7574
TIME...MOT...LOC 0127Z 244DEG 26KT 4000 7540 3965 7558 

HAIL...1.00IN
WIND...60MPH
 
$$

Staarmann

2 follow-up statements

826 
WWUS51 KPHI 180146
SVSPHI

Severe Weather Statement
National Weather Service Mount Holly NJ
946 PM EDT Sat Jul 17 2021

PAC029-180156-
/O.CAN.KPHI.SV.W.0197.000000T0000Z-210718T0215Z/
Chester PA-
946 PM EDT Sat Jul 17 2021

...THE SEVERE THUNDERSTORM WARNING FOR SOUTHEASTERN CHESTER COUNTY IS
CANCELLED...

The storms which prompted the warning have moved out of the warned 
area. Therefore, the warning has been cancelled.

A Severe Thunderstorm Watch remains in effect until 1100 PM EDT for
northern Delaware...southern New Jersey...and southeastern
Pennsylvania.

LAT...LON 3998 7544 4006 7539 4020 7512 4014 7503
      3996 7512 3995 7514 3959 7531 3955 7569
      3967 7574
TIME...MOT...LOC 0146Z 248DEG 30KT 4000 7523 3987 7526 3966 7546 

$$

DEC003-NJC015-033-PAC045-091-101-180215-
/O.CON.KPHI.SV.W.0197.000000T0000Z-210718T0215Z/
New Castle DE-Salem NJ-Gloucester NJ-Montgomery PA-Philadelphia PA-
Delaware PA-
946 PM EDT Sat Jul 17 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 1015 PM EDT
FOR NORTHERN NEW CASTLE...NORTHWESTERN SALEM...NORTHWESTERN
GLOUCESTER...SOUTHEASTERN MONTGOMERY...PHILADELPHIA AND DELAWARE
COUNTIES...

At 946 PM EDT, severe thunderstorms were located along a line
extending from Roxborough to Philadelphia International Airport to
near Pennsville, moving east at 35 mph.

HAZARD...60 mph wind gusts and quarter size hail.

SOURCE...Radar indicated.

IMPACT...Minor damage to vehicles is possible. Wind damage to roofs, 
         siding, trees, and power lines is possible.

Locations impacted include...
Philadelphia, Camden, Wilmington, Newark, Chester, West Deptford,
Pennsville, Yeadon, Carneys Point, Conshohocken, Hatboro, Folcroft,
Ambler, Swarthmore, Elsmere, Paulsboro, New Castle, Penns Grove,
Salem and Jenkintown.

This includes the following highways...
 New Jersey Turnpike between exits 1 and 2.
 Pennsylvania Turnpike between mile markers 333 and 345.
 Interstate 95 in Pennsylvania between mile markers 0 and 16, and
between mile markers 21 and 23.
 Interstate 95 in Delaware between mile markers 3 and 23.
 Interstate 76 in Pennsylvania between mile markers 330 and 350.
 Interstate 295 in New Jersey between mile markers 0 and 21.
 Interstate 676 in Pennsylvania between mile markers 0 and 1.
 Interstate 476 in Pennsylvania between mile markers 0 and 19.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

Torrential rainfall is occurring with these storms, and may lead to
flash flooding. Do not drive your vehicle through flooded roadways.

&&

LAT...LON 3998 7544 4006 7539 4020 7512 4014 7503
      3996 7512 3995 7514 3959 7531 3955 7569
      3967 7574
TIME...MOT...LOC 0146Z 248DEG 30KT 4000 7523 3987 7526 3966 7546 

HAIL...1.00IN
WIND...60MPH
 
$$

Staarmann

248 
WWUS51 KPHI 180202
SVSPHI

Severe Weather Statement
National Weather Service Mount Holly NJ
1002 PM EDT Sat Jul 17 2021

DEC003-NJC015-033-PAC045-091-101-180215-
/O.CON.KPHI.SV.W.0197.000000T0000Z-210718T0215Z/
New Castle DE-Salem NJ-Gloucester NJ-Montgomery PA-Philadelphia PA-
Delaware PA-
1002 PM EDT Sat Jul 17 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 1015 PM EDT
FOR NORTHEASTERN NEW CASTLE...NORTHWESTERN SALEM...NORTHWESTERN
GLOUCESTER...SOUTHEASTERN MONTGOMERY...PHILADELPHIA AND EASTERN
DELAWARE COUNTIES...

At 1002 PM EDT, severe thunderstorms were located along a line
extending from Northeast Philadelphia to Golden Triangle to near
Woodstown, moving northeast at 35 mph.

HAZARD...60 mph wind gusts and quarter size hail.

SOURCE...Radar indicated.

IMPACT...Minor damage to vehicles is possible. Wind damage to roofs, 
         siding, trees, and power lines is possible.

Locations impacted include...
Philadelphia, Camden, Wilmington, Chester, West Deptford, Pennsville,
Yeadon, Carneys Point, Hatboro, Folcroft, Ambler, Swarthmore,
Paulsboro, Penns Grove, Salem, Jenkintown, Narberth, Woodstown,
National Park and East Lansdowne.

This includes the following highways...
 New Jersey Turnpike between exits 1 and 2.
 Pennsylvania Turnpike between mile markers 335 and 345.
 Interstate 95 in Pennsylvania between mile markers 2 and 16, and
between mile markers 21 and 23.
 Interstate 76 in Pennsylvania between mile markers 334 and 350.
 Interstate 295 in New Jersey between mile markers 0 and 21.
 Interstate 676 in Pennsylvania between mile markers 0 and 1.
 Interstate 476 in Pennsylvania between mile markers 0 and 3, and
near mile marker 7.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

Torrential rainfall is occurring with these storms, and may lead to
flash flooding. Do not drive your vehicle through flooded roadways.

&&

LAT...LON 3968 7553 3997 7533 4013 7526 4020 7512
      4014 7503 3996 7512 3995 7514 3959 7531
      3956 7556 3962 7559
TIME...MOT...LOC 0202Z 245DEG 30KT 4009 7501 3994 7505 3966 7541 

HAIL...1.00IN
WIND...60MPH
 
$$

Staarmann

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 17, 8:40 PM EDT	Special Weather Statement	PHI	Kent	35 min
Jul 17, 9:25 PM EDT	Areal Flood Advisory	PHI	New Castle	2 hr
Jul 17, 9:36 PM EDT	Flash Flood Warning	PHI	New Castle	2 hr
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
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, 9:48 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, 9:30 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

Severe Thunderstorm Warnings in Pennsylvania, 2021 Severe Thunderstorm Warnings in New Jersey, 2021 Severe Thunderstorm Warnings in Delaware, 2021 Every severe thunderstorm 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; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.