Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 2020

Severe Thunderstorm Warning 87, NWS Philadelphia/Mount Holly

June 28, 2020Chester County, Delaware County, Pennsylvania

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Jun 28, 2020, 5:09 PM EDT for Chester County, Delaware County, Pennsylvania. It was in force for 36 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: Jun 28, 2020, 5:09 PM EDT (21:09 UTC)
Expired: Jun 28, 2020, 5:45 PM EDT
In force: 36 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Hail: 1.25 in
Wind: 60.0 mph

Counties Chester County, PA, Delaware County, PA

The radar

The Philadelphia radar (KDIX), 93 km from the middle of the area, began a volume at 21:11 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
Jun 28, 5:15 PM EDT	TSTM WND DMG	1 Sse West Bradford Twp, PA	MPING REPORT OF TREE LIMBS DOWN AND SHINGLES BLOWN OFF.
Jun 28, 5:15 PM EDT	HAIL 0.25	1 Sse West Bradford Twp, PA	MPING REPORT.
Jun 28, 5:31 PM EDT	TSTM WND DMG	1 Se Birmingham Twp, PA	DOWNED TREE BLOCKING GENERAL WEEDON DRIVE. TIME ESTIMATED FROM RADAR.
Jun 28, 5:35 PM EDT	TSTM WND DMG	1 N Westtown, PA	DOWNED TREE BLOCKING WESTTOWN ROAD.

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, 9.2 hours before the alert went out and 198 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: 106 J/kg
Mixed-layer CIN: -97 J/kg
Mixed-layer LCL: 1209 m above ground
0-6 km bulk shear: 22 kt
0-1 km storm-relative helicity: 39 m²/s²
0-3 km storm-relative helicity: 73 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

202 
WUUS51 KPHI 282109
SVRPHI
PAC029-045-282145-
/O.NEW.KPHI.SV.W.0087.200628T2109Z-200628T2145Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Mount Holly NJ
509 PM EDT Sun Jun 28 2020

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 545 PM EDT.

* At 509 PM EDT, a severe thunderstorm was located over Marshallton,
  or near West Chester, moving east at 35 mph.

  HAZARD...60 mph wind gusts and half dollar 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,
  Swarthmore, Cheyney, Elam, Marshallton, Lima, Trout Lake, Chelsea,
  Radnor Township, Gradyville, Nether Providence Township, Broomall,
  Newtown Square, Chester Township, Concordville and Bryn Mawr.

This includes the following highways...
 Interstate 95 in Pennsylvania between mile markers 2 and 6.
 Interstate 476 in Pennsylvania between mile markers 0 and 13.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Protecting yourself from immediate threats to life and safety shall
take priority.  Whenever possible, as long as it does not cause
greater harm, all COVID-19 protective action guidance should be
followed.

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

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

&&

LAT...LON 4002 7583 4004 7533 4002 7532 4002 7531
      3999 7529 3984 7536 3982 7539 3990 7581
TIME...MOT...LOC 2109Z 271DEG 29KT 3996 7572 

HAIL...1.25IN
WIND...60MPH
 
$$

JEO

2 follow-up statements

093 
WWUS51 KPHI 282120
SVSPHI

Severe Weather Statement
National Weather Service Mount Holly NJ
520 PM EDT Sun Jun 28 2020

PAC029-045-282145-
/O.CON.KPHI.SV.W.0087.000000T0000Z-200628T2145Z/
Chester PA-Delaware PA-
520 PM EDT Sun Jun 28 2020

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 545 PM EDT
FOR EAST CENTRAL CHESTER AND DELAWARE COUNTIES...

At 520 PM EDT, a severe thunderstorm was located over West Chester,
moving east at 35 mph.

HAZARD...60 mph wind gusts and half dollar 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, Swarthmore, Cheyney,
Elam, Marshallton, Lima, Trout Lake, Chelsea, Radnor Township,
Gradyville, Nether Providence Township, Broomall, Newtown Square,
Chester Township, Concordville, Bryn Mawr and Drexel Hill.

This includes the following highways...
 Interstate 95 in Pennsylvania between mile markers 2 and 6.
 Interstate 476 in Pennsylvania between mile markers 0 and 13.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Protecting yourself from immediate threats to life and safety shall
take priority.  Whenever possible, as long as it does not cause
greater harm, all COVID-19 protective action guidance should be
followed.

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

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

&&

LAT...LON 4004 7533 4002 7532 4002 7531 3999 7529
      3984 7536 3982 7539 3989 7574 4002 7572
TIME...MOT...LOC 2120Z 271DEG 29KT 3996 7560 

HAIL...1.25IN
WIND...60MPH
 
$$

JEO

114 
WWUS51 KPHI 282137
SVSPHI

Severe Weather Statement
National Weather Service Mount Holly NJ
537 PM EDT Sun Jun 28 2020

PAC029-045-282147-
/O.EXP.KPHI.SV.W.0087.000000T0000Z-200628T2145Z/
Chester PA-Delaware PA-
537 PM EDT Sun Jun 28 2020

...THE SEVERE THUNDERSTORM WARNING FOR EAST CENTRAL CHESTER AND
DELAWARE COUNTIES WILL EXPIRE AT 545 PM EDT...
                
The storm which prompted the warning has weakened below severe
limits, and no longer poses an immediate threat to life or property.
Therefore, the warning will be allowed to expire.  However gusty
winds are still possible with this thunderstorm.

LAT...LON 4004 7533 4002 7532 4002 7531 3999 7529
      3984 7536 3982 7539 3989 7574 4002 7572
TIME...MOT...LOC 2137Z 271DEG 29KT 3996 7544 

$$

JEO

The office that day

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

Issued	Product	Office	Counties	Lasted
Jun 28, 2:02 PM EDT	Severe Thunderstorm Warning	PHI	Northampton	13 min
Jun 28, 3:20 PM EDT	Severe Thunderstorm Warning	PHI	Carbon, Monroe, Northampton	40 min
Jun 28, 4:28 PM EDT	Special Weather Statement	PHI	Lehigh	32 min
Jun 28, 5:06 PM EDT	Special Weather Statement	PHI	Lehigh	24 min
Jun 28, 5:14 PM EDT	Severe Thunderstorm Warning	PHI	Northampton	46 min
Jun 28, 5:56 PM EDT	Special Weather Statement	PHI	Berks	34 min

Nearby

Severe Thunderstorm Warnings in Pennsylvania, 2020 Every severe thunderstorm warning in 2020

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.