Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 254, NWS Philadelphia/Mount Holly

August 11, 20215 counties in Pennsylvania; Burlington County, Camden County, Gloucester County, New Jersey; New Castle County, Delaware

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Aug 11, 2021, 7:11 PM EDT for 5 counties in Pennsylvania; Burlington County, Camden County, Gloucester County, New Jersey; New Castle County, Delaware. It was in force for 49 min. 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: Aug 11, 2021, 7:11 PM EDT (23:11 UTC)
Expired: Aug 11, 2021, 8:00 PM EDT
In force: 49 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Hail: 0.75 in
Wind: 60.0 mph

Counties New Castle County, DE, Burlington County, NJ, Camden County, NJ, Gloucester County, NJ, Bucks County, PA, Chester County, PA, Delaware County, PA, Montgomery County, PA, Philadelphia County, PA

The radar

The Philadelphia radar (KDIX), 77 km from the middle of the area, began a volume at 23:13 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 11, 7:14 PM EDT	TSTM WND DMG	1 Nnw West Norriton, PA	TREE DOWN ON TOP OF WIRES AND BLOCKING THE STREET AT GALBRAITH AVE AND WEST MAIN STREET.
Aug 11, 7:15 PM EDT	TSTM WND DMG	1 N Willistown Twp, PA	TREE DOWN IN ROADWAY ON GOSHEN ROAD. TIME ESTIMATED FROM RADAR.
Aug 11, 7:33 PM EDT	TSTM WND DMG	Aston, PA	MULTIPLE LARGE (6-12INCH DIAMETER) TREE LIMBS DOWN IN ASTON PA.
Aug 11, 7:34 PM EDT	TSTM WND DMG	1 Nnw Brookhaven, PA	DOWNED TREE ON US-030, TIME ESTIMATED FROM RADAR.
Aug 11, 7:35 PM EDT	TSTM WND DMG	Ridley Park, PA	LARGE TREE DOWN ON A RESIDENTS DECK. REPORT VIA SOCIAL MEDIA WITH A PHOTO. TIME ESTIMATED FROM RADAR.

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

The watch it was issued in

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

Issued	Product	Office	Lasted
Aug 11, 3:02 PM EDT	Severe Thunderstorm Watch	SPC	6 hr

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 11.2 hours before the alert went out and 214 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: 553 J/kg
Mixed-layer CIN: -190 J/kg
Mixed-layer LCL: 1301 m above ground
0-6 km bulk shear: 13 kt
0-1 km storm-relative helicity: 20 m²/s²
0-3 km storm-relative helicity: 77 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

075 
WUUS51 KPHI 112311
SVRPHI
DEC003-NJC005-007-015-PAC017-029-045-091-101-120000-
/O.NEW.KPHI.SV.W.0254.210811T2311Z-210812T0000Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Mount Holly NJ
711 PM EDT Wed Aug 11 2021

The National Weather Service in Mount Holly NJ has issued a

* Severe Thunderstorm Warning for...
  Northeastern New Castle County in northern Delaware...
  Northwestern Camden County in southern New Jersey...
  Gloucester County in southern New Jersey...
  West central Burlington County in southern New Jersey...
  Montgomery County in southeastern Pennsylvania...
  Southeastern Bucks County in southeastern Pennsylvania...
  Eastern Chester County in southeastern Pennsylvania...
  Philadelphia County in southeastern Pennsylvania...
  Delaware County in southeastern Pennsylvania...

* Until 800 PM EDT.

* At 711 PM EDT, severe thunderstorms were located along a line
  extending from near Ambler to near Arden, moving east at 30 mph.

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

  SOURCE...Radar indicated. Also, these storms have a history of 
           producing wind damage in Chester County.

  IMPACT...Damage to roofs, siding, trees, and power lines is 
           possible.

* Locations impacted include...
  Philadelphia, Camden, Wilmington, West Chester, Gloucester City,
  Bensalem, Norristown, Chester, Deptford, West Deptford, Glassboro,
  Phoenixville, Lansdale, West Norriton, East Norriton, Bellmawr,
  Yeadon, Westtown, Woodbury and Pitman.

This includes the following highways...
 New Jersey Turnpike between exits 2 and 3.
 Pennsylvania Turnpike between mile markers 310 and 354.
 Northeast Extension between mile markers 21 and 34.
 Interstate 95 in Pennsylvania between mile markers 0 and 36.
 Interstate 95 in Delaware between mile markers 16 and 23.
 Interstate 76 in Pennsylvania between mile markers 327 and 351.
 Interstate 76 in New Jersey between mile markers 0 and 3.
 Interstate 295 in New Jersey between mile markers 9 and 31.
 Interstate 676 in Pennsylvania between mile markers 0 and 1.
 Interstate 676 in New Jersey between mile markers 0 and 4.
 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.

&&

LAT...LON 4031 7557 4032 7492 4029 7487 4027 7485
      3964 7512 3969 7532 3973 7538 3978 7541
      3975 7551 3979 7587
TIME...MOT...LOC 2311Z 285DEG 26KT 4017 7528 3978 7548 

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...0.75 IN
WIND THREAT...OBSERVED
MAX WIND GUST...60 MPH

$$

JEO

3 follow-up statements

022 
WWUS51 KPHI 112325
SVSPHI

Severe Weather Statement
National Weather Service Mount Holly NJ
725 PM EDT Wed Aug 11 2021

DEC003-NJC005-007-015-PAC017-029-045-091-101-120000-
/O.CON.KPHI.SV.W.0254.000000T0000Z-210812T0000Z/
New Castle DE-Camden NJ-Gloucester NJ-Burlington NJ-Montgomery PA-
Bucks PA-Chester PA-Philadelphia PA-Delaware PA-
725 PM EDT Wed Aug 11 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 800 PM EDT
FOR NORTHEASTERN NEW CASTLE...NORTHWESTERN CAMDEN...GLOUCESTER...WEST
CENTRAL BURLINGTON...MONTGOMERY...SOUTHEASTERN BUCKS...EASTERN
CHESTER...PHILADELPHIA AND DELAWARE COUNTIES...

At 725 PM EDT, severe thunderstorms were located along a line
extending from near Willow Grove to Beckett, moving east at 30 mph.

HAZARD...60 mph wind gusts.

SOURCE...Radar indicated.

IMPACT...Damage to roofs, siding, trees, and power lines is 
         possible.

Locations impacted include...
Philadelphia, Camden, Wilmington, West Chester, Gloucester City,
Bensalem, Norristown, Chester, Deptford, West Deptford, Glassboro,
Phoenixville, Lansdale, West Norriton, East Norriton, Bellmawr,
Yeadon, Westtown, Woodbury and Pitman.

This includes the following highways...
 New Jersey Turnpike between exits 2 and 3.
 Pennsylvania Turnpike between mile markers 316 and 354.
 Northeast Extension between mile markers 21 and 34.
 Interstate 95 in Pennsylvania between mile markers 0 and 36.
 Interstate 95 in Delaware between mile markers 16 and 23.
 Interstate 76 in Pennsylvania between mile markers 327 and 351.
 Interstate 76 in New Jersey between mile markers 0 and 3.
 Interstate 295 in New Jersey between mile markers 9 and 31.
 Interstate 676 in Pennsylvania between mile markers 0 and 1.
 Interstate 676 in New Jersey between mile markers 0 and 4.
 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.

Wind damage with these storms may occur before any rain or 
lightning. Do not wait for the sound of thunder before taking cover.
SEEK SHELTER IMMEDIATELY inside a sturdy structure and stay away from
windows.

&&

LAT...LON 4032 7492 4029 7487 4027 7485 3964 7512
      3969 7532 3973 7538 3978 7541 3975 7551
      3979 7574 4031 7548
TIME...MOT...LOC 2325Z 285DEG 26KT 4015 7517 3976 7537 

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...<.75 IN
WIND THREAT...OBSERVED
MAX WIND GUST...60 MPH

$$

JEO

282 
WWUS51 KPHI 112346
SVSPHI

Severe Weather Statement
National Weather Service Mount Holly NJ
746 PM EDT Wed Aug 11 2021

DEC003-PAC029-112356-
/O.CAN.KPHI.SV.W.0254.000000T0000Z-210812T0000Z/
New Castle DE-Chester PA-
746 PM EDT Wed Aug 11 2021

...THE SEVERE THUNDERSTORM WARNING FOR NORTHEASTERN NEW CASTLE AND
EASTERN CHESTER COUNTIES 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 900 PM EDT for
southern and central New Jersey...and southeastern Pennsylvania.

LAT...LON 3964 7512 3968 7525 3969 7532 3973 7538
      3975 7538 3977 7541 3982 7542 3982 7546
      4031 7521 4032 7492 4029 7487 4027 7485
TIME...MOT...LOC 2346Z 285DEG 26KT 4011 7499 3972 7519 

$$

NJC005-007-015-PAC017-045-091-101-120000-
/O.CON.KPHI.SV.W.0254.000000T0000Z-210812T0000Z/
Camden NJ-Gloucester NJ-Burlington NJ-Montgomery PA-Bucks PA-
Philadelphia PA-Delaware PA-
746 PM EDT Wed Aug 11 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 800 PM EDT
FOR NORTHWESTERN CAMDEN...GLOUCESTER...WEST CENTRAL BURLINGTON...
SOUTHEASTERN MONTGOMERY...SOUTHEASTERN BUCKS...PHILADELPHIA AND
EASTERN DELAWARE COUNTIES...

At 746 PM EDT, severe thunderstorms were located along a line
extending from near Northeast Philadelphia to Mullica Hill, moving
east at 30 mph.

HAZARD...60 mph wind gusts.

SOURCE...Radar indicated.

IMPACT...Damage to roofs, siding, trees, and power lines is 
         possible.

Locations impacted include...
Philadelphia, Camden, Gloucester City, Bensalem, Chester, Deptford,
West Deptford, Glassboro, Bellmawr, Yeadon, Woodbury, Pitman,
Doylestown, Clayton, Riverside, Conshohocken, Palmyra, Hatboro,
Folcroft and Ambler.

This includes the following highways...
 New Jersey Turnpike between exits 2 and 3.
 Pennsylvania Turnpike between mile markers 332 and 354.
 Northeast Extension between mile markers 21 and 22.
 Interstate 95 in Pennsylvania between mile markers 1 and 36.
 Interstate 76 in Pennsylvania between mile markers 331 and 351.
 Interstate 76 in New Jersey between mile markers 0 and 3.
 Interstate 295 in New Jersey between mile markers 9 and 31.
 Interstate 676 in Pennsylvania between mile markers 0 and 1.
 Interstate 676 in New Jersey between mile markers 0 and 4.
 Interstate 476 in Pennsylvania between mile markers 0 and 11, and
between mile markers 15 and 19.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Wind damage with these storms will occur before any rain or
lightning. Do not wait for the sound of thunder before taking cover.
SEEK SHELTER IMMEDIATELY inside a sturdy structure and stay away from
windows.

&&

LAT...LON 3964 7512 3968 7525 3969 7532 3973 7538
      3975 7538 3977 7541 3982 7542 3982 7546
      4031 7521 4032 7492 4029 7487 4027 7485
TIME...MOT...LOC 2346Z 285DEG 26KT 4011 7499 3972 7519 

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...<.75 IN
WIND THREAT...OBSERVED
MAX WIND GUST...60 MPH

$$

JEO

019 
WWUS51 KPHI 112354
SVSPHI

Severe Weather Statement
National Weather Service Mount Holly NJ
754 PM EDT Wed Aug 11 2021

NJC005-007-015-PAC017-045-091-101-120004-
/O.EXP.KPHI.SV.W.0254.000000T0000Z-210812T0000Z/
Camden NJ-Gloucester NJ-Burlington NJ-Montgomery PA-Bucks PA-
Philadelphia PA-Delaware PA-
754 PM EDT Wed Aug 11 2021

...THE SEVERE THUNDERSTORM WARNING FOR NORTHWESTERN CAMDEN...
GLOUCESTER...WEST CENTRAL BURLINGTON...SOUTHEASTERN MONTGOMERY...
SOUTHEASTERN BUCKS...PHILADELPHIA AND EASTERN DELAWARE COUNTIES WILL
EXPIRE AT 800 PM EDT...
            
The storms which prompted the warning have weakened below severe
limits, and no longer pose an immediate threat to life or property.
Therefore, the warning will be allowed to expire.  However gusty
winds are still possible with these thunderstorms.

A Severe Thunderstorm Watch remains in effect until 900 PM EDT for
southern and central New Jersey...and southeastern Pennsylvania.

LAT...LON 3964 7512 3968 7525 3969 7532 3973 7538
      3975 7538 3977 7541 3982 7542 3982 7546
      4031 7521 4032 7492 4029 7487 4027 7485
TIME...MOT...LOC 2354Z 285DEG 26KT 4011 7499 3972 7519 

$$

JEO

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 10, 8:02 PM EDT	Severe Thunderstorm Warning	PHI	Delaware, Philadelphia	43 min
Aug 10, 8:18 PM EDT	Severe Thunderstorm Warning	PHI	Chester, Delaware, Montgomery	42 min
Aug 10, 8:36 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Delaware, Montgomery, Philadelphia	39 min
Aug 10, 8:43 PM EDT	Areal Flood Advisory	PHI	Delaware, Montgomery, Philadelphia	2 hr
Aug 11, 2:56 PM EDT	Excessive Heat Watch	PHI	Berks, Bucks, Chester, Lehigh, Montgomery, Northampton	12 hr
Aug 11, 4:46 PM EDT	Special Weather Statement	PHI	Monroe	44 min
Aug 11, 4:58 PM EDT	Special Weather Statement	PHI	Berks	47 min
Aug 11, 5:20 PM EDT	Areal Flood Advisory	PHI	Carbon, Monroe	57 min
Aug 11, 5:48 PM EDT	Severe Thunderstorm Warning	PHI	Berks	57 min
Aug 11, 6:16 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Lehigh, Montgomery	44 min
Aug 11, 6:26 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Chester, Delaware, Montgomery	49 min
Aug 11, 6:48 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Lehigh, Montgomery, Northampton	42 min
Aug 11, 6:50 PM EDT	Areal Flood Advisory	PHI	Monroe, Northampton	3 hr
Aug 11, 7:04 PM EDT	Areal Flood Advisory	PHI	Berks, Bucks, Chester, Delaware, Lehigh, Montgomery and 2 more	2 hr
Aug 10, 8:23 PM EDT	Special Marine Warning	PHI		79 min
Aug 10, 9:07 PM EDT	Special Weather Statement	PHI	Burlington, Camden, Cumberland	23 min
Aug 11, 5:57 PM EDT	Special Weather Statement	PHI	Sussex	48 min
Aug 11, 6:32 PM EDT	Special Weather Statement	PHI	Morris, Sussex, Warren	28 min
Aug 11, 7:04 PM EDT	Severe Thunderstorm Warning	PHI	Morris, Sussex, Warren	41 min
Aug 11, 7:28 PM EDT	Flash Flood Warning	PHI	Morris, Warren	3 hr
Aug 11, 7:45 PM EDT	Special Weather Statement	PHI	Morris	45 min
Aug 11, 7:52 PM EDT	Special Weather Statement	PHI	Atlantic, Burlington, Camden, Gloucester, Mercer	53 min
Aug 11, 7:57 PM EDT	Special Weather Statement	PHI	Hunterdon, Middlesex, Somerset	48 min
Aug 10, 8:11 PM EDT	Special Weather Statement	PHI	New Castle	34 min
Aug 10, 9:09 PM EDT	Special Weather Statement	PHI	Sussex	36 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.