Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 6, NWS Philadelphia/Mount Holly

April 21, 20216 counties in Pennsylvania

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Apr 21, 2021, 12:17 PM EDT for 6 counties in Pennsylvania. It was in force for 43 min. 8 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: Apr 21, 2021, 12:17 PM EDT (16:17 UTC)
Expired: Apr 21, 2021, 1:00 PM EDT
In force: 43 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Hail: 0.75 in
Wind: 60.0 mph

Counties Berks County, PA, Bucks County, PA, Chester County, PA, Lehigh County, PA, Montgomery County, PA, Northampton County, PA

The radar

The Philadelphia radar (KDIX), 108 km from the middle of the area, began a volume at 16:19 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
Apr 21, 12:20 PM EDT	HAIL 0.25	2 Ssw District Twp, PA
Apr 21, 12:22 PM EDT	HAIL 1	1 S Boyertown, PA
Apr 21, 12:35 PM EDT	TSTM WND DMG	1 Ssw Allentown, PA	TREE DOWN ON WIRES NEAR LEHIGH PKWY. TIME ESTIMATED FROM RADAR.
Apr 21, 12:35 PM EDT	HAIL 0.25	Emmaus, PA
Apr 21, 12:40 PM EDT	HAIL 0.25	1 Wsw Bethlehem Twp, PA
Apr 21, 12:40 PM EDT	HAIL 0.5	2 Ene Bethlehem Twp, PA
Apr 21, 12:48 PM EDT	HAIL 0.25	Trumbauersville, PA
Apr 21, 12:50 PM EDT	HAIL 0.25	Harleysville, PA

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, 4.3 hours before the alert went out and 225 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: 8 J/kg
Mixed-layer CIN: -277 J/kg
Mixed-layer LCL: 1577 m above ground
0-6 km bulk shear: 39 kt
0-1 km storm-relative helicity: 128 m²/s²
0-3 km storm-relative helicity: 109 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

971 
WUUS51 KPHI 211617
SVRPHI
PAC011-017-029-077-091-095-211700-
/O.NEW.KPHI.SV.W.0006.210421T1617Z-210421T1700Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Mount Holly NJ
1217 PM EDT Wed Apr 21 2021

The National Weather Service in Mount Holly NJ has issued a

* Severe Thunderstorm Warning for...
  Southeastern Berks County in eastern Pennsylvania...
  Southeastern Lehigh County in eastern Pennsylvania...
  Northwestern Montgomery County in southeastern Pennsylvania...
  Northwestern Bucks County in southeastern Pennsylvania...
  North central Chester County in southeastern Pennsylvania...
  South central Northampton County in eastern Pennsylvania...

* Until 100 PM EDT.

* At 1216 PM EDT, a severe thunderstorm was located near Bally, or 14
  miles southwest of Allentown, moving east at 40 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...
  Allentown, Easton, Bethlehem, Pottstown, Lansdale, Emmaus,
  Quakertown, Perkasie, Wilson, Souderton, Hellertown, Chalfont,
  Hatfield, East Greenville, Topton, Schwenksville, Bally,
  Bechtelsville, Green Lane and Glendon.

This includes the following highways...
 Northeast Extension between mile markers 30 and 58.
 Interstate 78 in Pennsylvania between mile markers 48 and 74.

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.

&&

LAT...LON 4019 7578 4057 7571 4072 7525 4026 7521
TIME...MOT...LOC 1616Z 247DEG 35KT 4044 7565 

HAIL...0.75IN
WIND...60MPH
 
$$

Davis

3 follow-up statements

923 
WWUS51 KPHI 211625
SVSPHI

Severe Weather Statement
National Weather Service Mount Holly NJ
1225 PM EDT Wed Apr 21 2021

PAC011-017-029-077-091-095-211700-
/O.CON.KPHI.SV.W.0006.000000T0000Z-210421T1700Z/
Berks PA-Lehigh PA-Montgomery PA-Bucks PA-Chester PA-Northampton PA-
1225 PM EDT Wed Apr 21 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 100 PM EDT
FOR SOUTHEASTERN BERKS...SOUTHEASTERN LEHIGH...NORTHWESTERN
MONTGOMERY...NORTHWESTERN BUCKS...NORTHEASTERN CHESTER AND SOUTH
CENTRAL NORTHAMPTON COUNTIES...

At 1224 PM EDT, a severe thunderstorm was located over Zionsville, or
9 miles southwest of Allentown, moving northeast at 40 mph.

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

SOURCE...Trained weather spotters. A trained spotter just south of 
         Boyertown reported quarter size hail.

IMPACT...Minor damage to vehicles is possible. Wind damage to roofs, 
         siding, trees, and power lines is possible.

Locations impacted include...
Allentown, Easton, Bethlehem, Pottstown, Lansdale, Emmaus,
Quakertown, Perkasie, Wilson, Souderton, Hellertown, Chalfont,
Hatfield, East Greenville, Schwenksville, Bally, Bechtelsville, Green
Lane, Glendon and Pleasant Valley.

This includes the following highways...
 Northeast Extension between mile markers 30 and 58.
 Interstate 78 in Pennsylvania between mile markers 50 and 74.

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.

&&

LAT...LON 4020 7572 4059 7565 4072 7525 4026 7521
TIME...MOT...LOC 1624Z 247DEG 35KT 4047 7555 

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

JEO

805 
WWUS51 KPHI 211642
SVSPHI

Severe Weather Statement
National Weather Service Mount Holly NJ
1242 PM EDT Wed Apr 21 2021

PAC011-029-211651-
/O.CAN.KPHI.SV.W.0006.000000T0000Z-210421T1700Z/
Berks PA-Chester PA-
1242 PM EDT Wed Apr 21 2021

...THE SEVERE THUNDERSTORM WARNING FOR SOUTHEASTERN BERKS AND
NORTHEASTERN CHESTER COUNTIES IS CANCELLED...
    
The severe thunderstorm which prompted the warning has moved out of 
the warned area. Therefore, the warning has been cancelled.

A Severe Thunderstorm Watch remains in effect until 600 PM EDT for
eastern and southeastern Pennsylvania.

LAT...LON 4022 7559 4064 7546 4072 7525 4026 7521
TIME...MOT...LOC 1641Z 247DEG 35KT 4054 7535 

$$

PAC017-077-091-095-211700-
/O.CON.KPHI.SV.W.0006.000000T0000Z-210421T1700Z/
Lehigh PA-Montgomery PA-Bucks PA-Northampton PA-
1242 PM EDT Wed Apr 21 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 100 PM EDT
FOR SOUTHEASTERN LEHIGH...NORTHWESTERN MONTGOMERY...NORTHWESTERN
BUCKS AND SOUTH CENTRAL NORTHAMPTON COUNTIES...

At 1241 PM EDT, a severe thunderstorm was located near Pleasant
Valley, or 7 miles southeast of Allentown, moving northeast at 40
mph.

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

SOURCE...Trained weather spotters.

IMPACT...Minor damage to vehicles is possible. Wind damage to roofs, 
         siding, trees, and power lines is possible.

Locations impacted include...
Allentown, Easton, Bethlehem, Lansdale, Emmaus, Quakertown, Perkasie,
Wilson, Souderton, Hellertown, Chalfont, Hatfield, East Greenville,
Schwenksville, Green Lane, Glendon, Pleasant Valley, Fricks,
Zionsville and Spring Mount.

This includes the following highways...
 Northeast Extension between mile markers 30 and 50.
 Interstate 78 in Pennsylvania between mile markers 59 and 74.

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.

&&

LAT...LON 4022 7559 4064 7546 4072 7525 4026 7521
TIME...MOT...LOC 1641Z 247DEG 35KT 4054 7535 

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

Davis

698 
WWUS51 KPHI 211654
SVSPHI

Severe Weather Statement
National Weather Service Mount Holly NJ
1254 PM EDT Wed Apr 21 2021

PAC017-077-091-095-211704-
/O.EXP.KPHI.SV.W.0006.000000T0000Z-210421T1700Z/
Lehigh PA-Montgomery PA-Bucks PA-Northampton PA-
1254 PM EDT Wed Apr 21 2021

...THE SEVERE THUNDERSTORM WARNING FOR SOUTHEASTERN LEHIGH...
NORTHWESTERN MONTGOMERY...NORTHWESTERN BUCKS AND SOUTH CENTRAL
NORTHAMPTON COUNTIES WILL EXPIRE AT 100 PM EDT...
        
The storm which prompted the warning has moved out of the area.
Therefore, the warning will be allowed to expire.  However small hail
and gusty winds are still possible with this thunderstorm.

A Severe Thunderstorm Watch remains in effect until 600 PM EDT for
eastern and southeastern Pennsylvania.

LAT...LON 4022 7559 4064 7546 4072 7525 4026 7521
TIME...MOT...LOC 1654Z 247DEG 35KT 4058 7522 

$$

Davis

The office that day

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

Issued	Product	Office	Counties	Lasted
Apr 20, 8:48 PM EDT	Freeze Watch	PHI	Berks, Bucks, Lehigh, Montgomery, Northampton	7 hr
Apr 21, 3:26 AM EDT	Freeze Warning	PHI	Berks, Bucks, Chester, Lehigh, Montgomery, Northampton	30 hr
Apr 21, 12:03 PM EDT	Special Weather Statement	PHI	Chester, Lehigh	42 min
Apr 21, 12:25 PM EDT	Severe Thunderstorm Warning	PHI	Lehigh, Northampton	50 min
Apr 21, 12:54 PM EDT	Special Weather Statement	PHI	Delaware	36 min
Apr 21, 12:55 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Montgomery, Northampton	27 min
Apr 21, 1:10 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Chester, Delaware, Montgomery, Philadelphia	50 min
Apr 21, 1:17 PM EDT	Special Weather Statement	PHI	Bucks	58 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.