Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 244, NWS Philadelphia/Mount Holly

August 10, 2021Berks County, Chester County, Montgomery County, Pennsylvania

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Aug 10, 2021, 7:10 PM EDT for Berks County, Chester County, Montgomery County, Pennsylvania. It was in force for 65 min. 4 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 10, 2021, 7:10 PM EDT (23:10 UTC)
Expired: Aug 10, 2021, 8:15 PM EDT
In force: 65 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Hail: 0.75 in
Wind: 60.0 mph

Counties Berks County, PA, Chester County, PA, Montgomery County, PA

The radar

The Dover AFB radar (KDOX), 131 km from the middle of the area, began a volume at 23:12 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 10, 7:47 PM EDT	TSTM WND DMG	1 Nw West Marlborough T, PA	TREES AND WIRES DOWN ON DOE RUN RD. TIME ESTIMATED FROM RADAR.
Aug 10, 7:52 PM EDT	TSTM WND DMG	1 Wnw Oxford, PA	A DOWNED TREE BLOCKED THE SOUTHBOUND US-1 RAMP ONTO PA-472. TIME ESTIMATED FROM RADAR.
Aug 10, 7:55 PM EDT	TSTM WND DMG	Caln Twp, PA	A DOWNED TREE BLOCKED THE ROADWAY NEAR THE INTERSECTION OF HARVEST DR AND INGLESIDE DR. TIME ESTIMATED FROM RADAR.
Aug 10, 8:04 PM EDT	TSTM WND GST 51	1 Nne Penn Twp, PA	CWOP SITE AV669.

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

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 11.2 hours before the alert went out and 162 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: 529 J/kg
Mixed-layer CIN: -120 J/kg
Mixed-layer LCL: 1096 m above ground
0-6 km bulk shear: 14 kt
0-1 km storm-relative helicity: 37 m²/s²
0-3 km storm-relative helicity: 65 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

102 
WUUS51 KPHI 102310
SVRPHI
PAC011-029-091-110015-
/O.NEW.KPHI.SV.W.0244.210810T2310Z-210811T0015Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Mount Holly NJ
710 PM EDT Tue Aug 10 2021

The National Weather Service in Mount Holly NJ has issued a

* Severe Thunderstorm Warning for...
  South central Berks County in eastern Pennsylvania...
  West central Montgomery County in southeastern Pennsylvania...
  Central Chester County in southeastern Pennsylvania...

* Until 815 PM EDT.

* At 709 PM EDT, severe thunderstorms were located along a line
  extending from Churchtown to Stewartstown, moving southeast at 15
  mph.

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

  SOURCE...Radar indicated.

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

* Locations impacted include...
  Phoenixville, Coatesville, Downingtown, Collegeville, Oxford,
  Royersford, Parkesburg, Trappe, Honey Brook, Elverson, New Morgan,
  Homeville, Glen Roy, Cochranville, Pughtown, Mount Vernon,
  Lionville-Marchwood, Glenmoore, Chester Springs and Lionville.

This includes the following highways...
 Pennsylvania Turnpike between mile markers 296 and 315.
 Interstate 176 in Pennsylvania between mile markers 1 and 7.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

In addition to large hail and damaging winds, frequent cloud to
ground lightning is occurring with these storms. Move indoors
immediately. Remember, if you can hear thunder, you are close enough
to be struck by lightning.

&&

LAT...LON 3974 7612 3973 7610 3974 7610 3976 7606
      3983 7604 3987 7599 3995 7600 4004 7593
      4011 7594 4014 7588 4024 7604 4026 7602
      4022 7542 3972 7601 3972 7613
TIME...MOT...LOC 2309Z 293DEG 13KT 4015 7599 3974 7656 

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

$$

SFJ

2 follow-up statements

795 
WWUS51 KPHI 102338
SVSPHI

Severe Weather Statement
National Weather Service Mount Holly NJ
738 PM EDT Tue Aug 10 2021

PAC011-029-091-110015-
/O.CON.KPHI.SV.W.0244.000000T0000Z-210811T0015Z/
Berks PA-Montgomery PA-Chester PA-
738 PM EDT Tue Aug 10 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 815 PM EDT
FOR SOUTH CENTRAL BERKS...WEST CENTRAL MONTGOMERY AND CENTRAL CHESTER
COUNTIES...

At 738 PM EDT, severe thunderstorms were located along a line
extending from near Glenmoore to near Delta, moving east at 15 mph.

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

SOURCE...Radar indicated.

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

Locations impacted include...
Phoenixville, Coatesville, Downingtown, Collegeville, Oxford,
Royersford, Parkesburg, Trappe, Honey Brook, Elverson, New Morgan,
Homeville, Glen Roy, Cochranville, Pughtown, Mount Vernon,
Lionville-Marchwood, Glenmoore, Chester Springs and Lionville.

This includes the following highways...
 Pennsylvania Turnpike between mile markers 296 and 315.
 Interstate 176 in Pennsylvania between mile markers 1 and 7.

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 these storms.
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 3974 7612 3973 7610 3974 7610 3976 7606
      3983 7604 3987 7599 3995 7600 4004 7593
      4011 7594 4014 7588 4024 7604 4026 7602
      4022 7542 3972 7601 3972 7613
TIME...MOT...LOC 2338Z 291DEG 14KT 4011 7582 3970 7639 

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

$$

SFJ

336 
WWUS51 KPHI 102350
SVSPHI

Severe Weather Statement
National Weather Service Mount Holly NJ
750 PM EDT Tue Aug 10 2021

PAC011-091-102359-
/O.CAN.KPHI.SV.W.0244.000000T0000Z-210811T0015Z/
Berks PA-Montgomery PA-
750 PM EDT Tue Aug 10 2021

...THE SEVERE THUNDERSTORM WARNING FOR SOUTH CENTRAL BERKS AND WEST
CENTRAL MONTGOMERY COUNTIES IS CANCELLED...

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

LAT...LON 3976 7606 3981 7603 3983 7604 3983 7602
      3987 7599 3993 7600 3994 7598 3995 7600
      4004 7593 4011 7594 4014 7587 4014 7552
      3972 7601 3972 7612
TIME...MOT...LOC 2349Z 293DEG 13KT 4010 7578 3969 7635 

$$

PAC029-110015-
/O.CON.KPHI.SV.W.0244.000000T0000Z-210811T0015Z/
Chester PA-
750 PM EDT Tue Aug 10 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 815 PM EDT
FOR CENTRAL CHESTER COUNTY...

At 749 PM EDT, severe thunderstorms were located along a line
extending from Glenmoore to near Delta, moving southeast at 15 mph.

HAZARD...70 mph wind gusts and penny size hail.

SOURCE...Radar indicated.

IMPACT...Expect considerable tree damage. Damage is likely to mobile 
         homes, roofs, and outbuildings.

Locations impacted include...
Phoenixville, Coatesville, Downingtown, Oxford, Parkesburg, Honey
Brook, Homeville, Glen Roy, Cochranville, Glenmoore, Chester Springs,
Lionville, Mount Vernon, Lionville-Marchwood, Atglen, South
Coatesville, Modena, Thorndale and Exton.

This includes Pennsylvania Turnpike between mile markers 303 and 315.
 
PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

This is a DANGEROUS SITUATION. These storms are producing widespread 
wind damage across Lancaster County. SEEK SHELTER NOW inside a 
sturdy structure and stay away from windows.
 
&&

LAT...LON 3976 7606 3981 7603 3983 7604 3983 7602
      3987 7599 3993 7600 3994 7598 3995 7600
      4004 7593 4011 7594 4014 7587 4014 7552
      3972 7601 3972 7612
TIME...MOT...LOC 2349Z 293DEG 13KT 4010 7578 3969 7635 

THUNDERSTORM DAMAGE THREAT...CONSIDERABLE
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...0.75 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...70 MPH

$$

SFJ

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 9, 10:10 PM EDT	Areal Flood Advisory	PHI	Carbon	3 hr
Aug 10, 3:33 AM EDT	Excessive Heat Warning	PHI	Berks, Bucks, Chester, Delaware, Lehigh, Montgomery and 2 more	4 days
Aug 10, 3:33 AM EDT	Heat Advisory	PHI	Berks, Carbon, Lehigh, Monroe, Northampton	4 days
Aug 10, 5:58 AM EDT	Flash Flood Warning	PHI	Bucks	2 hr
Aug 10, 3:06 PM EDT	Special Weather Statement	PHI	Berks	24 min
Aug 10, 3:33 PM EDT	Special Weather Statement	PHI	Berks	27 min
Aug 10, 3:52 PM EDT	Special Weather Statement	PHI	Berks, Carbon, Lehigh	23 min
Aug 10, 4:01 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Carbon, Chester, Lehigh, Montgomery, Northampton	44 min
Aug 10, 4:18 PM EDT	Areal Flood Advisory	PHI	Berks, Carbon, Lehigh	3 hr
Aug 10, 4:33 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Bucks, Carbon, Chester, Lehigh, Monroe and 2 more	42 min
Aug 10, 5:05 PM EDT	Special Weather Statement	PHI	Northampton	25 min
Aug 10, 5:09 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Montgomery, Philadelphia	51 min
Aug 10, 5:11 PM EDT	Special Weather Statement	PHI	Chester, Montgomery, Philadelphia	34 min
Aug 10, 5:40 PM EDT	Special Weather Statement	PHI	Chester	35 min
Aug 10, 5:58 PM EDT	Special Weather Statement	PHI	Philadelphia	32 min
Aug 10, 6:36 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Chester	39 min
Aug 10, 7:54 PM EDT	Severe Thunderstorm Warning Considerable damage threat	PHI	Chester	51 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.