Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 10, NWS Philadelphia/Mount Holly

April 21, 2021Bucks County, Montgomery County, Northampton County, Pennsylvania; Hunterdon County, Warren County, New Jersey

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Apr 21, 2021, 12:55 PM EDT for Bucks County, Montgomery County, Northampton County, Pennsylvania; Hunterdon County, Warren County, New Jersey. It was in force for 27 min. 6 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, 12:55 PM EDT (16:55 UTC)
Expired: Apr 21, 2021, 1:22 PM EDT
In force: 27 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Hail: 1.0 in
Wind: 60.0 mph

Counties Hunterdon County, NJ, Warren County, NJ, Bucks County, PA, Montgomery County, PA, Northampton County, PA

The radar

The Philadelphia radar (KDIX), 86 km from the middle of the area, began a volume at 16:56 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, 12:58 PM EDT	HAIL 0.5	Kintnersville, PA
Apr 21, 1:03 PM EDT	HAIL 0.88	Collegeville, PA
Apr 21, 1:05 PM EDT	TSTM WND DMG	Upper Black Eddy, PA	LARGE TREE DOWN.
Apr 21, 1:05 PM EDT	TSTM WND GST 46	1 Ene Pohatcong Twp, NJ
Apr 21, 1:10 PM EDT	TSTM WND DMG	3 N Alexandria Twp, NJ	TREE DOWN ON WIRES ON RICK RD. TIME ESTIMATED FROM RADAR.
Apr 21, 1:20 PM EDT	TSTM WND DMG	1 Wsw Clinton, NJ	DOWNED TREE ON I-78 EASTBOUND RAMP TO EXIT 15. ONE LANE WAS CLOSED. 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
Apr 21, 12:28 PM EDT	Severe Thunderstorm Watch	SPC	5 hr

The nearest sounding before it

Brookhaven, NY (KOKX), launched 12:00Z, 4.9 hours before the alert went out and 184 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 1427 m above ground
0-6 km bulk shear: 37 kt
0-1 km storm-relative helicity: 206 m²/s²
0-3 km storm-relative helicity: 201 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

215 
WUUS51 KPHI 211655
SVRPHI
NJC019-041-PAC017-091-095-211745-
/O.NEW.KPHI.SV.W.0010.210421T1655Z-210421T1745Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Mount Holly NJ
1255 PM EDT Wed Apr 21 2021

The National Weather Service in Mount Holly NJ has issued a

* Severe Thunderstorm Warning for...
  Hunterdon County in northwestern New Jersey...
  Southwestern Warren County in northwestern New Jersey...
  Central Montgomery County in southeastern Pennsylvania...
  Bucks County in southeastern Pennsylvania...
  Southeastern Northampton County in eastern Pennsylvania...

* Until 145 PM EDT.

* At 1255 PM EDT, severe thunderstorms were located along a line
  extending from near Glendon to near Trappe, 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...
  Easton, Lansdale, Quakertown, Perkasie, Doylestown, Byram, Wilson,
  Hatboro, Souderton, Bedminster, Washington, Collegeville,
  Flemington, Chalfont, Tinicum, High Bridge, Trappe, Hatfield,
  Clinton and New Hope.

This includes the following highways...
 Pennsylvania Turnpike near mile marker 346.
 Northeast Extension between mile markers 25 and 40.
 Interstate 78 in Pennsylvania between mile markers 73 and 76.
 Interstate 78 in New Jersey between mile markers 0 and 23.

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 4074 7483 4073 7475 4016 7501 4018 7552
      4068 7525 4078 7487
TIME...MOT...LOC 1655Z 255DEG 32KT 4063 7521 4022 7544 

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

Davis

2 follow-up statements

427 
WWUS51 KPHI 211715
SVSPHI

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

PAC091-095-211724-
/O.CAN.KPHI.SV.W.0010.000000T0000Z-210421T1745Z/
Montgomery PA-Northampton PA-
115 PM EDT Wed Apr 21 2021

...THE SEVERE THUNDERSTORM WARNING FOR CENTRAL MONTGOMERY AND
SOUTHEASTERN NORTHAMPTON COUNTIES IS CANCELLED...

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

A Severe Thunderstorm Watch remains in effect until 600 PM EDT for
central, northern and northwestern New Jersey...and southeastern
Pennsylvania.

LAT...LON 4074 7483 4073 7475 4027 7496 4033 7526
      4070 7512 4078 7487
TIME...MOT...LOC 1714Z 255DEG 32KT 4067 7500 4026 7523 

$$

NJC019-041-PAC017-211745-
/O.CON.KPHI.SV.W.0010.000000T0000Z-210421T1745Z/
Hunterdon NJ-Warren NJ-Bucks PA-
115 PM EDT Wed Apr 21 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 145 PM EDT
FOR HUNTERDON...SOUTHWESTERN WARREN AND CENTRAL BUCKS COUNTIES...

At 114 PM EDT, severe thunderstorms were located along a line
extending from near Hampton to near Chalfont, 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...
Doylestown, Byram, Bedminster, Flemington, Tinicum, High Bridge,
Clinton, New Hope, Dublin, Glen Gardner, Ferndale, Hampton,
Frenchtown, Lebanon, Milford, Califon, Bloomsbury, Stockton, Revere
and Lumberville.

This includes Interstate 78 in New Jersey between mile markers 5 and
23.
 
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 4074 7483 4073 7475 4027 7496 4033 7526
      4070 7512 4078 7487
TIME...MOT...LOC 1714Z 255DEG 32KT 4067 7500 4026 7523 

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

Davis

104 
WWUS51 KPHI 211722
SVSPHI

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

NJC019-041-PAC017-211731-
/O.CAN.KPHI.SV.W.0010.000000T0000Z-210421T1745Z/
Hunterdon NJ-Warren NJ-Bucks PA-
122 PM EDT Wed Apr 21 2021

...THE SEVERE THUNDERSTORM WARNING FOR HUNTERDON...SOUTHWESTERN
WARREN AND CENTRAL BUCKS COUNTIES IS CANCELLED...
            
The storms which prompted the warning have weakened below severe
limits, and no longer pose an immediate threat to life or property.
Therefore, the warning has been cancelled.  However small hail and
gusty winds are still possible with these thunderstorms.

A Severe Thunderstorm Watch remains in effect until 600 PM EDT for
central, northern and northwestern New Jersey...and southeastern
Pennsylvania.

LAT...LON 4074 7483 4073 7475 4027 7496 4033 7526
      4070 7512 4078 7487
TIME...MOT...LOC 1720Z 255DEG 32KT 4068 7493 4028 7516 

$$

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, 12:17 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Bucks, Chester, Lehigh, Montgomery, Northampton	43 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, 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
Apr 21, 12:51 PM EDT	Severe Thunderstorm Warning	PHI	Sussex, Warren	21 min
Apr 21, 1:28 PM EDT	Severe Thunderstorm Warning	PHI	Atlantic, Burlington, Camden, Gloucester	36 min
Apr 21, 1:30 PM EDT	Special Marine Warning	PHI		60 min
Apr 21, 1:43 PM EDT	Severe Thunderstorm Warning	PHI	Hunterdon, Middlesex, Morris, Somerset	33 min
Apr 21, 1:58 PM EDT	Special Weather Statement	PHI	Burlington, Camden, Monmouth, Ocean	62 min
Apr 21, 2:02 PM EDT	Severe Thunderstorm Warning	PHI	Burlington, Camden, Monmouth, Ocean	43 min
Apr 21, 2:03 PM EDT	Special Weather Statement	PHI	Cumberland	27 min
Apr 21, 2:17 PM EDT	Severe Thunderstorm Warning	PHI	Atlantic, Cumberland, Gloucester, Salem	43 min
Apr 21, 2:28 PM EDT	Special Weather Statement	PHI	Middlesex, Monmouth	47 min
Apr 21, 2:30 PM EDT	Special Marine Warning	PHI		60 min
Apr 21, 2:38 PM EDT	Severe Thunderstorm Warning	PHI	Monmouth, Ocean	37 min
Apr 21, 2:40 PM EDT	Special Marine Warning	PHI		55 min
Apr 21, 2:43 PM EDT	Special Weather Statement	PHI	Cape May	32 min
Apr 21, 2:50 PM EDT	Severe Thunderstorm Warning	PHI	Atlantic, Burlington, Ocean	40 min
Apr 21, 3:02 PM EDT	Severe Thunderstorm Warning	PHI	Atlantic	28 min
Apr 21, 3:07 PM EDT	Special Marine Warning	PHI		53 min

Nearby

Severe Thunderstorm Warnings in Pennsylvania, 2021 Severe Thunderstorm Warnings in New Jersey, 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.