Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 2017

Severe Thunderstorm Warning 163, NWS Philadelphia/Mount Holly

August 18, 2017Berks County, Bucks County, Montgomery County, Pennsylvania

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Aug 18, 2017, 4:24 PM EDT for Berks County, Bucks County, Montgomery County, Pennsylvania. It was in force for 51 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued: Aug 18, 2017, 4:24 PM EDT (20:24 UTC)
Expired: Aug 18, 2017, 5:15 PM EDT
In force: 51 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Tornado: Possible
Hail: 1.0 in
Wind: 60.0 mph

Counties Berks County, PA, Bucks County, PA, Montgomery County, PA

The radar

The Philadelphia radar (KDIX), 107 km from the middle of the area, began a volume at 20:25 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.

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 18, 2:27 PM EDT	Severe Thunderstorm Watch	SPC	9 hr

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 8.4 hours before the alert went out and 220 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: 746 J/kg
Mixed-layer CIN: -72 J/kg
Mixed-layer LCL: 651 m above ground
0-6 km bulk shear: 26 kt
0-1 km storm-relative helicity: 12 m²/s²
0-3 km storm-relative helicity: 76 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.3

Open this sounding in Storm Lab

The text

As transmitted.

515 
WUUS51 KPHI 182024
SVRPHI
PAC011-017-091-182115-
/O.NEW.KPHI.SV.W.0163.170818T2024Z-170818T2115Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Mount Holly NJ
424 PM EDT FRI AUG 18 2017

The National Weather Service in Mount Holly NJ has issued a

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

* Until 515 PM EDT

* At 424 PM EDT, a severe thunderstorm was located near
  Bechtelsville, or 12 miles east of Reading, moving east at 25 mph.

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

  SOURCE...Radar indicated. 

  IMPACT...Minor damage to vehicles is possible. Expect damage to 
           trees and power lines. 

* Locations impacted include...
  Norristown, Pottstown, Lansdale, West Norriton, East Norriton,
  Perkasie, Souderton, Collegeville, Trappe, Hatfield, East
  Greenville, Dublin, Schwenksville, Bally, Bechtelsville, Green
  Lane, Lyons, Fricks, Spring Mount and Geryville.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Remain alert for a possible tornado! Tornadoes can develop quickly
from severe thunderstorms. If you spot a tornado go at once into the
basement or small central room in a sturdy structure.

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

&&

LAT...LON 4048 7576 4043 7549 4042 7549 4043 7548
      4037 7520 4012 7532 4022 7559 4024 7560
      4024 7561 4023 7560 4031 7584
TIME...MOT...LOC 2024Z 289DEG 21KT 4037 7571 

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

SFJ

2 follow-up statements

159 
WWUS51 KPHI 182041
SVSPHI

Severe Weather Statement
National Weather Service Mount Holly NJ
441 PM EDT FRI AUG 18 2017

PAC011-017-091-182115-
/O.CON.KPHI.SV.W.0163.000000T0000Z-170818T2115Z/
Berks PA-Montgomery PA-Bucks PA-
441 PM EDT FRI AUG 18 2017

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 515 PM EDT
FOR EAST CENTRAL BERKS...NORTHWESTERN MONTGOMERY AND WEST CENTRAL
BUCKS COUNTIES...

At 441 PM EDT, a severe thunderstorm was located over Gilbertsville,
or 18 miles east of Reading, moving east at 25 mph.

HAZARD...70 mph wind gusts and quarter size hail. 

SOURCE...Radar indicated. 

IMPACT...Minor damage to vehicles is possible. Expect considerable 
         tree damage. Wind damage is also likely to mobile homes, 
         roofs, and outbuildings. 

Locations impacted include...
Norristown, Pottstown, Lansdale, West Norriton, East Norriton,
Perkasie, Souderton, Collegeville, Trappe, Hatfield, East Greenville,
Dublin, Schwenksville, Bally, Bechtelsville, Green Lane, Fricks,
Spring Mount, Geryville and Gilbertsville.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Remain alert for a possible tornado! Tornadoes can develop quickly
from severe thunderstorms. If you spot a tornado go at once into the
basement or small central room in a sturdy structure.

This is a very dangerous storm! 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 4043 7549 4042 7549 4037 7520 4012 7532
      4022 7559 4024 7560 4024 7561 4023 7560
      4027 7573 4046 7565
TIME...MOT...LOC 2041Z 289DEG 21KT 4034 7559 

TORNADO...POSSIBLE
HAIL...1.00IN
WIND...70MPH
 
$$

SFJ

277 
WWUS51 KPHI 182058
SVSPHI

Severe Weather Statement
National Weather Service Mount Holly NJ
458 PM EDT FRI AUG 18 2017

PAC011-017-091-182115-
/O.CON.KPHI.SV.W.0163.000000T0000Z-170818T2115Z/
Berks PA-Montgomery PA-Bucks PA-
458 PM EDT FRI AUG 18 2017

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 515 PM EDT
FOR EAST CENTRAL BERKS...NORTHWESTERN MONTGOMERY AND WEST CENTRAL
BUCKS COUNTIES...

At 458 PM EDT, a severe thunderstorm was located near Green Lane, or
16 miles south of Allentown, moving east at 30 mph.

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

SOURCE...Radar indicated. 

IMPACT...Expect damage to trees and power lines. 

Locations impacted include...
Norristown, Pottstown, Lansdale, West Norriton, East Norriton,
Perkasie, Souderton, Collegeville, Trappe, Hatfield, Dublin,
Schwenksville, Green Lane, Fricks, Spring Mount, Geryville,
Gilbertsville, Skippack, Stowe and Telford.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Remain alert for a possible tornado! Tornadoes can develop quickly
from severe thunderstorms. If you spot a tornado go at once into the
basement or small central room in a sturdy structure.

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 4033 7553 4042 7549 4037 7520 4012 7532
      4022 7559 4024 7560 4024 7561 4023 7560
      4027 7573 4034 7570
TIME...MOT...LOC 2058Z 271DEG 24KT 4036 7541 

TORNADO...POSSIBLE
HAIL...0.88IN
WIND...60MPH
 
$$

SFJ

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 18, 3:39 AM EDT	Flash Flood Watch	PHI	Berks, Bucks, Chester, Delaware, Lehigh, Montgomery and 2 more	18 hr
Aug 18, 4:48 AM EDT	Areal Flood Advisory	PHI	Berks, Lehigh, Northampton	4 hr
Aug 18, 2:10 PM EDT	Areal Flood Advisory	PHI	Berks, Carbon, Lehigh	4 hr
Aug 18, 2:21 PM EDT	Special Weather Statement	PHI	Berks	24 min
Aug 18, 2:33 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Lehigh	42 min
Aug 18, 3:14 PM EDT	Special Weather Statement	PHI	Berks, Lehigh	31 min
Aug 18, 3:15 PM EDT	Areal Flood Advisory	PHI	Berks	4 hr
Aug 18, 3:19 PM EDT	Special Weather Statement	PHI	Northampton	26 min
Aug 18, 3:37 PM EDT	Special Weather Statement	PHI	Carbon	38 min
Aug 18, 3:43 PM EDT	Special Weather Statement	PHI	Berks	32 min
Aug 18, 3:45 PM EDT	Areal Flood Advisory	PHI	Carbon, Lehigh, Monroe, Northampton	4 hr
Aug 18, 3:46 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Lehigh, Montgomery, Northampton	44 min
Aug 18, 4:02 PM EDT	Flash Flood Warning	PHI	Berks	4 hr
Aug 18, 4:29 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Chester, Montgomery	61 min
Aug 18, 4:57 PM EDT	Areal Flood Advisory	PHI	Bucks, Chester, Montgomery	3 hr
Aug 18, 5:03 PM EDT	Severe Thunderstorm Warning	PHI	Chester	42 min
Aug 18, 5:11 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Chester, Delaware, Montgomery, Philadelphia	49 min
Aug 18, 5:20 PM EDT	Areal Flood Advisory	PHI	Bucks, Delaware, Montgomery, Philadelphia	3 hr
Aug 18, 5:39 PM EDT	Severe Thunderstorm Warning	PHI	Chester, Delaware, Philadelphia	66 min
Aug 18, 5:54 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Montgomery, Philadelphia	66 min
Aug 18, 6:38 PM EDT	Special Weather Statement	PHI	Delaware, Philadelphia	37 min

Nearby

Severe Thunderstorm Warnings in Pennsylvania, 2017 Every severe thunderstorm warning in 2017

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.