Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 211, NWS Philadelphia/Mount Holly

July 21, 2021Chester County, Delaware County, Pennsylvania

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Jul 21, 2021, 2:52 PM EDT for Chester County, Delaware County, Pennsylvania. It was in force for 38 min. 1 report 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, 2:52 PM EDT (18:52 UTC)
Expired: Jul 21, 2021, 3:30 PM EDT
In force: 38 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Hail: 1.0 in
Wind: 60.0 mph

Counties Chester County, PA, Delaware County, PA

The radar

The Philadelphia radar (KDIX), 114 km from the middle of the area, began a volume at 18:54 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, 3:40 PM EDT	TSTM WND DMG	1 Wnw Chester Twp, PA	WIRES DOWN ON CARTER AVENUE IN CHESTER TOWNSHIP. 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
Jul 21, 11:56 AM EDT	Severe Thunderstorm Watch	SPC	7 hr

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 6.9 hours before the alert went out and 179 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: 638 J/kg
Mixed-layer CIN: -61 J/kg
Mixed-layer LCL: 1275 m above ground
0-6 km bulk shear: 32 kt
0-1 km storm-relative helicity: -12 m²/s²
0-3 km storm-relative helicity: 95 m²/s²
Significant tornado parameter: 0.0
Supercell composite: -0.1

Open this sounding in Storm Lab

The text

As transmitted.

999 
WUUS51 KPHI 211852
SVRPHI
PAC029-045-211930-
/O.NEW.KPHI.SV.W.0211.210721T1852Z-210721T1930Z/

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

The National Weather Service in Mount Holly NJ has issued a

* Severe Thunderstorm Warning for...
  Central Chester County in southeastern Pennsylvania...
  Delaware County in southeastern Pennsylvania...

* Until 330 PM EDT.

* At 251 PM EDT, a severe thunderstorm was located over Parkesburg,
  or 12 miles southeast of New Holland, moving east 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...
  West Chester, Chester, Coatesville, Westtown, Downingtown,
  Parkesburg, Cochranville, Cheyney, Elam, Marshallton, Lima,
  Chelsea, Radnor Township, Lionville-Marchwood, Gradyville, Paoli,
  Newtown Square, Chester Township, Lionville and Concordville.

This includes the following highways...
 Interstate 95 in Pennsylvania between mile markers 1 and 4.
 Interstate 476 in Pennsylvania between mile markers 12 and 13.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4004 7593 4007 7593 4005 7535 3982 7538
      3981 7539 3984 7550 3984 7560 3989 7599
      3992 7600 3994 7598 3995 7600
TIME...MOT...LOC 1851Z 276DEG 25KT 3997 7592 

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

NC

2 follow-up statements

640 
WWUS51 KPHI 211917
SVSPHI

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

PAC029-045-211930-
/O.CON.KPHI.SV.W.0211.000000T0000Z-210721T1930Z/
Chester PA-Delaware PA-
317 PM EDT Wed Jul 21 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 330 PM EDT
FOR EAST CENTRAL CHESTER AND DELAWARE COUNTIES...

At 317 PM EDT, a severe thunderstorm was located near West Chester,
moving east at 40 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...
West Chester, Chester, Westtown, Downingtown, Cheyney, Elam,
Marshallton, Lima, Chelsea, Radnor Township, Lionville-Marchwood,
Gradyville, Paoli, Newtown Square, Chester Township, Lionville,
Concordville, Nether Providence Township, Broomall and West Goshen.

This includes the following highways...
 Interstate 95 in Pennsylvania between mile markers 1 and 4.
 Interstate 476 in Pennsylvania between mile markers 12 and 13.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Frequent cloud to ground lightning is occurring with this storm. Move
indoors immediately. Lightning is one of nature's leading killers.
Remember, if you can hear thunder, you are close enough to be struck
by lightning.

&&

LAT...LON 4006 7575 4005 7535 3982 7538 3981 7539
      3984 7550 3984 7560 3987 7580
TIME...MOT...LOC 1917Z 286DEG 33KT 3991 7562 

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

Gorse

671 
WWUS51 KPHI 211928
SVSPHI

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

PAC029-045-211937-
/O.EXP.KPHI.SV.W.0211.000000T0000Z-210721T1930Z/
Chester PA-Delaware PA-
328 PM EDT Wed Jul 21 2021

...THE SEVERE THUNDERSTORM WARNING FOR EAST CENTRAL CHESTER AND
DELAWARE COUNTIES WILL EXPIRE AT 330 PM EDT...
    
The severe storm has moved out of most of Chester County, however a 
severe thunderstorm warning remains in effect for Camden and 
Glouchester Counties through 4 PM.

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


LAT...LON 4006 7575 4005 7535 3982 7538 3981 7539
      3984 7550 3984 7560 3987 7580
TIME...MOT...LOC 1927Z 276DEG 25KT 3989 7556 

$$

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, 2:48 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Montgomery, Philadelphia	42 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.