Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 297, NWS Philadelphia/Mount Holly

September 8, 20214 counties in Pennsylvania

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Sep 8, 2021, 10:47 PM EDT for 4 counties in Pennsylvania. It was in force for 58 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: Sep 8, 2021, 10:47 PM EDT (02:47 UTC)
Expired: Sep 8, 2021, 11:45 PM EDT
In force: 58 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Tornado: Possible
Hail: 0.75 in
Wind: 60.0 mph

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

The radar

The Philadelphia radar (KDIX), 124 km from the middle of the area, began a volume at 02:48 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
Sep 8, 10:48 PM EDT	TSTM WND DMG	Shillington, PA	TREE AND WIRES DOWN ON 601 BROBST STREET IN SHILLINGTON BOROUGH. TIME ESTIMATED FROM RADAR.
Sep 8, 10:50 PM EDT	TSTM WND DMG	Exeter Twp, PA	LARGE BRANCHES AND WIRES DOWN IN EXETER TOWNSHIP, TIME ESTIMATED FROM RADAR.
Sep 8, 10:55 PM EDT	TSTM WND GST 61	1 Ne Reading, PA	WIND GUST MEASURED AT SITE EW3190 (ELEVATION 1115 FT).
Sep 8, 10:58 PM EDT	TSTM WND DMG	2 N Mount Penn, PA	TREE ON WIRES ON ANGORA ROAD IN LOWER ALSACE 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
Sep 8, 7:54 PM EDT	Severe Thunderstorm Watch	SPC	4 hr

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 00:00Z, 2.8 hours before the alert went out and 213 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: 1652 J/kg
Mixed-layer CIN: -18 J/kg
Mixed-layer LCL: 1146 m above ground
0-6 km bulk shear: 43 kt
0-1 km storm-relative helicity: 115 m²/s²
0-3 km storm-relative helicity: 136 m²/s²
Significant tornado parameter: 1.0
Supercell composite: 7.0

Open this sounding in Storm Lab

The text

As transmitted.

520 
WUUS51 KPHI 090247
SVRPHI
PAC011-077-091-095-090345-
/O.NEW.KPHI.SV.W.0297.210909T0247Z-210909T0345Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Mount Holly NJ
1047 PM EDT Wed Sep 8 2021

The National Weather Service in Mount Holly NJ has issued a

* Severe Thunderstorm Warning for...
  Berks County in eastern Pennsylvania...
  Lehigh County in eastern Pennsylvania...
  Northwestern Montgomery County in southeastern Pennsylvania...
  West central Northampton County in eastern Pennsylvania...

* Until 1145 PM EDT.

* At 1047 PM EDT, severe thunderstorms were located along a line
  extending from near Lenhartsville to near Wyomissing, 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, Reading, Bethlehem, Pottstown, Emmaus, Wyomissing,
  Northampton, Birdsboro, Kutztown, Fleetwood, Sinking Spring,
  Laureldale, East Greenville, Bath, Topton, Leesport,
  Shoemakersville, Bally, Bechtelsville and Lyons.

This includes the following highways...
 Northeast Extension between mile markers 48 and 66.
 Interstate 78 in Pennsylvania between mile markers 34 and 60.
 Interstate 176 in Pennsylvania between mile markers 5 and 11.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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

&&

LAT...LON 4067 7592 4075 7539 4024 7554 4023 7563
      4024 7565 4023 7572 4021 7599 4025 7605
TIME...MOT...LOC 0247Z 250DEG 36KT 4059 7582 4031 7594 

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

$$

JEO

3 follow-up statements

295 
WWUS51 KPHI 090307
SVSPHI

Severe Weather Statement
National Weather Service Mount Holly NJ
1107 PM EDT Wed Sep 8 2021

PAC011-077-091-095-090345-
/O.CON.KPHI.SV.W.0297.000000T0000Z-210909T0345Z/
Berks PA-Lehigh PA-Montgomery PA-Northampton PA-
1107 PM EDT Wed Sep 8 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 1145 PM EDT
FOR EASTERN BERKS...LEHIGH...NORTHWESTERN MONTGOMERY AND WEST CENTRAL
NORTHAMPTON COUNTIES...

At 1106 PM EDT, severe thunderstorms were located along a line
extending from Coffeetown to near Bechtelsville, moving east at 40
mph.

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

SOURCE...Emergency management. These storms have a history of 
         producing tree and power line damage in Berks County.

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

Locations impacted include...
Allentown, Reading, Bethlehem, Pottstown, Emmaus, Wyomissing,
Northampton, Birdsboro, Kutztown, Fleetwood, Laureldale, East
Greenville, Bath, Topton, Bally, Bechtelsville, Lyons, Neffs,
Coffeetown and New Tripoli.

This includes the following highways...
 Northeast Extension between mile markers 48 and 65.
 Interstate 78 in Pennsylvania between mile markers 38 and 60.
 Interstate 176 in Pennsylvania between mile markers 5 and 11.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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

&&

LAT...LON 4066 7586 4075 7539 4024 7554 4023 7563
      4024 7565 4023 7572 4021 7599 4025 7605
      4036 7591
TIME...MOT...LOC 0306Z 250DEG 36KT 4065 7559 4037 7571 

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

$$

JEO

800 
WWUS51 KPHI 090316
SVSPHI

Severe Weather Statement
National Weather Service Mount Holly NJ
1116 PM EDT Wed Sep 8 2021

PAC011-077-091-095-090345-
/O.CON.KPHI.SV.W.0297.000000T0000Z-210909T0345Z/
Berks PA-Lehigh PA-Montgomery PA-Northampton PA-
1116 PM EDT Wed Sep 8 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 1145 PM EDT
FOR EAST CENTRAL BERKS...CENTRAL LEHIGH...NORTHWESTERN MONTGOMERY AND
WEST CENTRAL NORTHAMPTON COUNTIES...

At 1115 PM EDT, severe thunderstorms were located along a line
extending from Northampton to Bally, moving east at 40 mph.

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

SOURCE...Emergency management. These storms have a history of 
         producing tree and power line damage in Berks County.

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

Locations impacted include...
Allentown, Bethlehem, Emmaus, Northampton, East Greenville, Bath,
Topton, Bally, Bechtelsville, Neffs, Coffeetown, Zionsville, Ancient
Oaks, Claussville, Schnecksville, Gilbertsville, Catasauqua,
Boyertown, Pennsburg and Coplay.

This includes the following highways...
 Northeast Extension between mile markers 48 and 65.
 Interstate 78 in Pennsylvania between mile markers 47 and 60.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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

&&

LAT...LON 4069 7569 4075 7539 4034 7551 4032 7563
      4031 7581 4033 7583 4037 7583 4052 7572
TIME...MOT...LOC 0315Z 250DEG 36KT 4068 7548 4040 7560 

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

$$

JEO

981 
WWUS51 KPHI 090342
SVSPHI

Severe Weather Statement
National Weather Service Mount Holly NJ
1142 PM EDT Wed Sep 8 2021

PAC011-077-091-095-090352-
/O.EXP.KPHI.SV.W.0297.000000T0000Z-210909T0345Z/
Berks PA-Lehigh PA-Montgomery PA-Northampton PA-
1142 PM EDT Wed Sep 8 2021

...THE SEVERE THUNDERSTORM WARNING FOR EAST CENTRAL BERKS...CENTRAL
LEHIGH...NORTHWESTERN MONTGOMERY AND WEST CENTRAL NORTHAMPTON
COUNTIES WILL EXPIRE AT 1145 PM EDT...
    
The storms which prompted the warning have moved out of the area.
Therefore, the warning will be allowed to expire.

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

LAT...LON 4069 7569 4075 7539 4034 7551 4032 7563
      4031 7581 4033 7583 4037 7583 4052 7572
TIME...MOT...LOC 0342Z 250DEG 36KT 4077 7516 4049 7528 

$$

JEO

The office that day

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

Issued	Product	Office	Counties	Lasted
Sep 8, 8:47 PM EDT	Special Weather Statement	PHI	Northampton	28 min
Sep 8, 9:12 PM EDT	Special Weather Statement	PHI	Lehigh	48 min
Sep 8, 9:16 PM EDT	Areal Flood Advisory	PHI	Lehigh, Northampton	3 hr
Sep 8, 9:16 PM EDT	Special Weather Statement	PHI	Northampton	29 min
Sep 8, 9:38 PM EDT	Special Weather Statement	PHI	Berks	52 min
Sep 8, 9:46 PM EDT	Special Weather Statement	PHI	Lehigh, Northampton	44 min
Sep 8, 9:48 PM EDT	Flash Flood Warning	PHI	Lehigh, Northampton	7 hr
Sep 8, 9:59 PM EDT	Areal Flood Advisory	PHI	Berks	3 hr
Sep 8, 10:11 PM EDT	Severe Thunderstorm Warning	PHI	Berks	49 min
Sep 8, 10:23 PM EDT	Tornado Warning	PHI	Berks	22 min
Sep 8, 10:27 PM EDT	Special Weather Statement	PHI	Northampton	33 min
Sep 8, 10:42 PM EDT	Flash Flood Warning	PHI	Northampton	6 hr
Sep 8, 10:47 PM EDT	Areal Flood Advisory	PHI	Carbon, Monroe	3 hr
Sep 8, 10:56 PM EDT	Special Weather Statement	PHI	Northampton	34 min
Sep 8, 11:27 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Lehigh, Northampton	48 min
Sep 8, 11:35 PM EDT	Special Weather Statement	PHI	Chester, Delaware, Montgomery	40 min
Sep 9, 12:08 AM EDT	Special Weather Statement	PHI	Bucks, Delaware, Montgomery, Philadelphia	37 min
Sep 9, 4:26 AM EDT	Areal Flood Warning	PHI	Lehigh, Northampton	3 hr
Sep 9, 4:28 AM EDT	Areal Flood Warning	PHI	Northampton	4 hr

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.