Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 210, NWS Philadelphia/Mount Holly

July 21, 2021Bucks County, Montgomery County, Philadelphia County, Pennsylvania

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Jul 21, 2021, 2:48 PM EDT for Bucks County, Montgomery County, Philadelphia County, Pennsylvania. It was in force for 42 min. 18 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 21, 2021, 2:48 PM EDT (18:48 UTC)
Expired: Jul 21, 2021, 3:30 PM EDT
In force: 42 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Hail: 1.0 in
Wind: 60.0 mph

Counties Bucks 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 18:49 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 21, 2:50 PM EDT	HAIL 0.88	Schwenksville, PA
Jul 21, 3:05 PM EDT	TSTM WND DMG	East Norriton, PA	NUMEROUS TREES DOWN.
Jul 21, 3:05 PM EDT	HAIL 1	East Norriton, PA
Jul 21, 3:07 PM EDT	TSTM WND DMG	North Wales, PA	PHOTO OF LARGE TREE DOWN IN UPPER GWYNEDD TOWNSHIP. TIME ESTIMATED FROM RADAR.
Jul 21, 3:10 PM EDT	TSTM WND DMG	1 Wnw Blue Bell, PA	NUMEROUS TREES DOWN ON WIRES IN WHITPAIN TOWNSHIP. TIME ESTIMATED FROM RADAR.
Jul 21, 3:10 PM EDT	TSTM WND GST 51	Plymouth Meeting, PA
Jul 21, 3:10 PM EDT	HAIL 1	Plymouth Meeting, PA
Jul 21, 3:11 PM EDT	HAIL 1	Plymouth Twp, PA	HAIL, TO THE SIZE OF QUARTERS (FROM MPING).
Jul 21, 3:15 PM EDT	TSTM WND DMG	2 Wnw Blue Bell, PA	NUMEROUS PHOTOS OF LARGE TREE LIMBS DOWN IN THE IN THE CENTER SQUARE AREA OF BLUE BELL. TIME ESTIMATED FROM RADAR.
Jul 21, 3:15 PM EDT	HAIL 1.25	Blue Bell, PA	PHOTOS RELAYED ON SOCIAL MEDIA, OF HAIL SLIGHTLY LARGER THAN QUARTER SIZE. TIME ESTIMATED FROM RADAR.
Jul 21, 3:20 PM EDT	TSTM WND DMG	1 S Fort Washington, PA	TREES DOWN NEAR THE PENNSYLVANIA TURNPIKE.
Jul 21, 3:20 PM EDT	TSTM WND GST 55	Fort Washington, PA	MESOWEST.
Jul 21, 3:25 PM EDT	HAIL 1	Flourtown, PA	PHOTO FROM SOCIAL MEDIA, HAIL ESTIMATED AT QUARTER SIZE IN FLOURTOWN. TIME ESTIMATED FROM RADAR.
Jul 21, 3:28 PM EDT	TSTM WND DMG	Abington, PA	LARGE TREE SHEARED APART IN ABINGTON TOWNSHIP. PHOTO RELAYED ON SOCIAL MEDIA. TIME ESTIMATED FROM RADAR.
Jul 21, 3:30 PM EDT	HAIL 1	Abington, PA
Jul 21, 3:30 PM EDT	HAIL 1	Glenside, PA
Jul 21, 3:30 PM EDT	HAIL 1	Jenkintown, PA
Jul 21, 3:40 PM EDT	TSTM WND DMG	2 Nw Holmesburg, PA	TREES ON WIRES ON STANWOOD ST IN RHAWNHURST.

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
Jul 21, 11:56 AM EDT	Severe Thunderstorm Watch	SPC	7 hr

The nearest sounding before it

Brookhaven, NY (KOKX), launched 12:00Z, 6.8 hours before the alert went out and 220 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: 130 J/kg
Mixed-layer CIN: -165 J/kg
Mixed-layer LCL: 1495 m above ground
0-6 km bulk shear: 35 kt
0-1 km storm-relative helicity: 22 m²/s²
0-3 km storm-relative helicity: 48 m²/s²
Significant tornado parameter: 0.0
Supercell composite: -0.0

Open this sounding in Storm Lab

The text

As transmitted.

606 
WUUS51 KPHI 211848
SVRPHI
PAC017-091-101-211930-
/O.NEW.KPHI.SV.W.0210.210721T1848Z-210721T1930Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Mount Holly NJ
248 PM EDT Wed Jul 21 2021

The National Weather Service in Mount Holly NJ has issued a

* Severe Thunderstorm Warning for...
  Montgomery County in southeastern Pennsylvania...
  Southeastern Bucks County in southeastern Pennsylvania...
  Northern Philadelphia County in southeastern Pennsylvania...

* Until 330 PM EDT.

* At 248 PM EDT, a severe thunderstorm was located over
  Schwenksville, or 20 miles north of West Chester, 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, Bensalem, Norristown, Phoenixville, Lansdale, West
  Norriton, East Norriton, Conshohocken, Hatboro, Souderton, Ambler,
  Collegeville, Royersford, Jenkintown, Trappe, Hatfield, Beverly,
  Rockledge, Abington and Langhorne.

This includes the following highways...
 Pennsylvania Turnpike between mile markers 331 and 355.
 Northeast Extension between mile markers 21 and 35.
 Interstate 95 in Pennsylvania between mile markers 27 and 29, and
between mile markers 32 and 38.
 Interstate 476 in Pennsylvania between mile markers 18 and 19.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4035 7551 4019 7485 4007 7492 4007 7494
      4003 7503 4000 7506 4015 7551 4016 7551
      4017 7553 4021 7556 4020 7558
TIME...MOT...LOC 1848Z 292DEG 29KT 4024 7548 

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

NC

2 follow-up statements

344 
WWUS51 KPHI 211905
SVSPHI

Severe Weather Statement
National Weather Service Mount Holly NJ
305 PM EDT Wed Jul 21 2021

PAC017-091-101-211930-
/O.CON.KPHI.SV.W.0210.000000T0000Z-210721T1930Z/
Montgomery PA-Bucks PA-Philadelphia PA-
305 PM EDT Wed Jul 21 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 330 PM EDT
FOR CENTRAL MONTGOMERY...SOUTHEASTERN BUCKS AND NORTHERN PHILADELPHIA
COUNTIES...

At 305 PM EDT, a severe thunderstorm was located over East Norriton,
or 15 miles northwest of Philadelphia, moving east at 35 mph.

HAZARD...70 mph wind gusts and half dollar size hail.

SOURCE...Radar indicated.

IMPACT...Minor damage to vehicles is possible. Expect considerable 
         tree damage. Wind damage is also likely to mobile homes, 
         roofs, and outbuildings.

Locations impacted include...
Philadelphia, Bensalem, Norristown, Lansdale, West Norriton, East
Norriton, Hatboro, Souderton, Ambler, Collegeville, Jenkintown,
Hatfield, Beverly, Rockledge, Abington, Langhorne, Bryn Athyn,
Ivyland, Wissinoming and Feasterville-Trevose.

This includes the following highways...
 Pennsylvania Turnpike between mile markers 331 and 355.
 Northeast Extension between mile markers 21 and 35.
 Interstate 95 in Pennsylvania between mile markers 27 and 29, and
between mile markers 32 and 38.
 Interstate 476 in Pennsylvania near mile marker 19.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4032 7539 4019 7485 4007 7492 4007 7494
      4003 7503 4000 7506 4014 7544 4016 7546
      4018 7547
TIME...MOT...LOC 1905Z 292DEG 29KT 4019 7531 

HAIL...1.25IN
WIND...70MPH
 
$$

NC

522 
WWUS51 KPHI 211929
SVSPHI

Severe Weather Statement
National Weather Service Mount Holly NJ
329 PM EDT Wed Jul 21 2021

PAC017-091-101-211939-
/O.EXP.KPHI.SV.W.0210.000000T0000Z-210721T1930Z/
Montgomery PA-Bucks PA-Philadelphia PA-
329 PM EDT Wed Jul 21 2021

...THE SEVERE THUNDERSTORM WARNING FOR CENTRAL MONTGOMERY...
SOUTHEASTERN BUCKS AND NORTHERN PHILADELPHIA COUNTIES WILL EXPIRE AT
330 PM EDT...
    
The severe thunderstorm which prompted the warning has moved out of 
the warned area. Therefore, the warning will be allowed to expire.

A Severe Thunderstorm Watch remains in effect until 800 PM EDT for
southern New Jersey...and southeastern Pennsylvania.

Remember, a Severe Thunderstorm Warning still remains in effect for
southern Montgomery County and Philadelphia county through 4PM

LAT...LON 4032 7539 4019 7485 4007 7492 4007 7494
      4003 7503 4000 7506 4014 7544 4016 7546
      4018 7547
TIME...MOT...LOC 1929Z 292DEG 29KT 4012 7508 

$$

NC

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 21, 1:08 PM EDT	Special Weather Statement	PHI	Lehigh	37 min
Jul 21, 1:11 PM EDT	Special Weather Statement	PHI	Northampton	34 min
Jul 21, 1:27 PM EDT	Severe Thunderstorm Warning	PHI	Berks	48 min
Jul 21, 2:03 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Lehigh, Northampton	42 min
Jul 21, 2:14 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Bucks, Chester, Delaware, Montgomery	19 min
Jul 21, 2:41 PM EDT	Special Weather Statement	PHI	Montgomery	49 min
Jul 21, 2:52 PM EDT	Severe Thunderstorm Warning	PHI	Chester, Delaware	38 min
Jul 21, 3:16 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Montgomery, Philadelphia	44 min
Jul 21, 3:27 PM EDT	Severe Thunderstorm Warning	PHI	Chester, Delaware, Philadelphia	33 min
Jul 21, 3:48 PM EDT	Severe Thunderstorm Warning	PHI	Bucks	42 min
Jul 21, 5:59 PM EDT	Special Weather Statement	PHI	Berks	31 min

Nearby

Severe Thunderstorm Warnings in Pennsylvania, 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.