Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 2021
Severe Thunderstorm Warning 252, NWS Philadelphia/Mount Holly
NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Aug 11, 2021, 6:48 PM EDT for 4 counties in Pennsylvania. It was in force for 42 min. 1 report 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 11, 2021, 6:48 PM EDT (22:48 UTC)
- Expired
- Aug 11, 2021, 7:30 PM EDT
- In force
- 42 min
- Issued by
- NWS Philadelphia/Mount Holly
- Area
- Storm-based polygon
- Hail
- 0.75 in
- Wind
- 60.0 mph
Counties Bucks County, PA, Lehigh County, PA, Montgomery County, PA, Northampton County, PA
The radar
The Philadelphia radar (KDIX), 95 km from the middle of the area, began a volume at 22:52 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 11, 7:10 PM EDT | TSTM WND DMG | 2 N Dublin, PA | A FEW REPORTS OF POWER OUTAGES DUE TO TREE DAMAGE IN THE DUBLIN AREA, INCLUDING NEAR IRISH MEETINGHOUSE RD. LIKELY ASSOCIATED WITH OUTFLOW WINDS. 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 |
|---|---|---|---|
| Aug 11, 3:02 PM EDT | Severe Thunderstorm Watch | SPC | 6 hr |
The nearest sounding before it
Brookhaven, NY (KOKX), launched 12:00Z, 10.8 hours before the alert went out and 211 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.
- Mixed-layer CAPE
- 977 J/kg
- Mixed-layer CIN
- -44 J/kg
- Mixed-layer LCL
- 711 m above ground
- 0-6 km bulk shear
- 15 kt
- 0-1 km storm-relative helicity
- 29 m²/s²
- 0-3 km storm-relative helicity
- 18 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
709
WUUS51 KPHI 112248
SVRPHI
PAC017-077-091-095-112330-
/O.NEW.KPHI.SV.W.0252.210811T2248Z-210811T2330Z/
BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Mount Holly NJ
648 PM EDT Wed Aug 11 2021
The National Weather Service in Mount Holly NJ has issued a
* Severe Thunderstorm Warning for...
Southeastern Lehigh County in eastern Pennsylvania...
Northern Montgomery County in southeastern Pennsylvania...
Northwestern Bucks County in southeastern Pennsylvania...
South central Northampton County in eastern Pennsylvania...
* Until 730 PM EDT.
* At 646 PM EDT, a severe thunderstorm was located near Green Lane,
or 19 miles south of Allentown, moving east at 45 mph.
HAZARD...60 mph wind gusts and penny size hail.
SOURCE...Radar indicated. These storms have a history of producing
tree and utility damage.
IMPACT...Damage to roofs, siding, trees, and power lines is
possible.
* Locations impacted include...
Allentown, Bethlehem, Lansdale, Emmaus, Quakertown, Perkasie,
Doylestown, Byram, Souderton, Bedminster, Hellertown, Chalfont,
Tinicum, Hatfield, East Greenville, Dublin, Ferndale,
Schwenksville, Riegelsville and Green Lane.
This includes the following highways...
Northeast Extension between mile markers 27 and 52.
Interstate 78 in Pennsylvania between mile markers 58 and 67.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
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 4040 7557 4044 7553 4046 7555 4063 7548
4059 7531 4059 7519 4057 7518 4058 7512
4055 7508 4048 7506 4046 7507 4035 7503
4017 7525 4032 7560
TIME...MOT...LOC 2246Z 269DEG 40KT 4031 7553
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...0.75 IN
WIND THREAT...OBSERVED
MAX WIND GUST...60 MPH
$$
JEO3 follow-up statements
311
WWUS51 KPHI 112301
SVSPHI
Severe Weather Statement
National Weather Service Mount Holly NJ
701 PM EDT Wed Aug 11 2021
PAC095-112311-
/O.CAN.KPHI.SV.W.0252.000000T0000Z-210811T2330Z/
Northampton PA-
701 PM EDT Wed Aug 11 2021
...THE SEVERE THUNDERSTORM WARNING FOR SOUTH CENTRAL NORTHAMPTON
COUNTY IS CANCELLED...
The severe thunderstorm which prompted the warning has weakened.
Therefore, the warning has been cancelled.
A Severe Thunderstorm Watch remains in effect until 900 PM EDT for
eastern and southeastern Pennsylvania.
LAT...LON 4040 7557 4042 7551 4045 7547 4048 7545
4047 7533 4045 7522 4043 7513 4043 7507
4035 7503 4017 7525 4032 7560
TIME...MOT...LOC 2301Z 269DEG 40KT 4031 7531
$$
PAC017-077-091-112330-
/O.CON.KPHI.SV.W.0252.000000T0000Z-210811T2330Z/
Lehigh PA-Montgomery PA-Bucks PA-
701 PM EDT Wed Aug 11 2021
...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 730 PM EDT
FOR SOUTHERN LEHIGH...NORTHERN MONTGOMERY AND WEST CENTRAL BUCKS
COUNTIES...
At 701 PM EDT, a severe thunderstorm was located over Souderton, or
21 miles southeast of Allentown, moving east at 45 mph.
HAZARD...60 mph wind gusts.
SOURCE...Radar indicated.
IMPACT...Damage to roofs, siding, trees, and power lines is
possible.
Locations impacted include...
Lansdale, Quakertown, Perkasie, Doylestown, Souderton, Bedminster,
Chalfont, Hatfield, East Greenville, Dublin, Schwenksville, Green
Lane, Fricks, Spring Mount, Geryville, Pipersville, Gardenville,
Gilbertsville, Skippack and Telford.
This includes Northeast Extension between mile markers 27 and 46.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
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 4040 7557 4042 7551 4045 7547 4048 7545
4047 7533 4045 7522 4043 7513 4043 7507
4035 7503 4017 7525 4032 7560
TIME...MOT...LOC 2301Z 269DEG 40KT 4031 7531
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...<.75 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH
$$
JEO869
WWUS51 KPHI 112317
SVSPHI
Severe Weather Statement
National Weather Service Mount Holly NJ
717 PM EDT Wed Aug 11 2021
PAC017-077-091-112330-
/O.CON.KPHI.SV.W.0252.000000T0000Z-210811T2330Z/
Lehigh PA-Montgomery PA-Bucks PA-
717 PM EDT Wed Aug 11 2021
...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 730 PM EDT
FOR SOUTHERN LEHIGH...NORTHERN MONTGOMERY AND WEST CENTRAL BUCKS
COUNTIES...
At 717 PM EDT, a severe thunderstorm was located near Doylestown, or
17 miles west of Trenton, moving east at 45 mph.
HAZARD...60 mph wind gusts.
SOURCE...Radar indicated.
IMPACT...Damage to roofs, siding, trees, and power lines is
possible.
Locations impacted include...
Lansdale, Quakertown, Perkasie, Doylestown, Souderton, Bedminster,
Chalfont, Hatfield, Dublin, Schwenksville, Green Lane, Fricks, Spring
Mount, Geryville, Pipersville, Gardenville, Telford, Sellersville,
Pennsburg and North Wales.
This includes Northeast Extension between mile markers 27 and 46.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
For your protection move to an interior room on the lowest floor of a
building.
Torrential rainfall is occurring with this storm, and may lead to
flash flooding. Do not drive your vehicle through flooded roadways.
&&
LAT...LON 4038 7550 4041 7549 4045 7547 4048 7545
4047 7533 4045 7522 4043 7513 4043 7507
4035 7503 4017 7525 4031 7557
TIME...MOT...LOC 2317Z 269DEG 40KT 4031 7507
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...<.75 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH
$$
JEO828
WWUS51 KPHI 112327
SVSPHI
Severe Weather Statement
National Weather Service Mount Holly NJ
727 PM EDT Wed Aug 11 2021
PAC017-077-091-112337-
/O.EXP.KPHI.SV.W.0252.000000T0000Z-210811T2330Z/
Lehigh PA-Montgomery PA-Bucks PA-
727 PM EDT Wed Aug 11 2021
...THE SEVERE THUNDERSTORM WARNING FOR SOUTHERN LEHIGH...NORTHERN
MONTGOMERY AND WEST CENTRAL BUCKS COUNTIES WILL EXPIRE AT 730 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.
A Severe Thunderstorm Watch remains in effect until 900 PM EDT for
eastern and southeastern Pennsylvania.
LAT...LON 4038 7550 4041 7549 4045 7547 4048 7545
4047 7533 4045 7522 4043 7513 4043 7507
4035 7503 4017 7525 4031 7557
TIME...MOT...LOC 2327Z 269DEG 40KT 3995 7527
$$
JEOThe office that day
Everything else NWS Philadelphia/Mount Holly issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 10, 8:02 PM EDT | Severe Thunderstorm Warning | PHI | Delaware, Philadelphia | 43 min |
| Aug 10, 8:18 PM EDT | Severe Thunderstorm Warning | PHI | Chester, Delaware, Montgomery | 42 min |
| Aug 10, 8:36 PM EDT | Severe Thunderstorm Warning | PHI | Bucks, Delaware, Montgomery, Philadelphia | 39 min |
| Aug 10, 8:43 PM EDT | Areal Flood Advisory | PHI | Delaware, Montgomery, Philadelphia | 2 hr |
| Aug 11, 2:56 PM EDT | Excessive Heat Watch | PHI | Berks, Bucks, Chester, Lehigh, Montgomery, Northampton | 12 hr |
| Aug 11, 4:46 PM EDT | Special Weather Statement | PHI | Monroe | 44 min |
| Aug 11, 4:58 PM EDT | Special Weather Statement | PHI | Berks | 47 min |
| Aug 11, 5:20 PM EDT | Areal Flood Advisory | PHI | Carbon, Monroe | 57 min |
| Aug 11, 5:48 PM EDT | Severe Thunderstorm Warning | PHI | Berks | 57 min |
| Aug 11, 6:16 PM EDT | Severe Thunderstorm Warning | PHI | Berks, Lehigh, Montgomery | 44 min |
| Aug 11, 6:26 PM EDT | Severe Thunderstorm Warning | PHI | Berks, Chester, Delaware, Montgomery | 49 min |
| Aug 11, 6:50 PM EDT | Areal Flood Advisory | PHI | Monroe, Northampton | 3 hr |
| Aug 11, 7:04 PM EDT | Areal Flood Advisory | PHI | Berks, Bucks, Chester, Delaware, Lehigh, Montgomery and 2 more | 2 hr |
| Aug 11, 7:11 PM EDT | Severe Thunderstorm Warning | PHI | Bucks, Chester, Delaware, Montgomery, Philadelphia | 49 min |
Nearby
Severe Thunderstorm Warnings in Pennsylvania, 2021Every 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.