Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 2018

Severe Thunderstorm Warning 18, NWS Philadelphia/Mount Holly

May 15, 2018Chester County, Pennsylvania

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at May 15, 2018, 5:12 PM EDT for Chester County, Pennsylvania. It was in force for 63 min. 2 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: May 15, 2018, 5:12 PM EDT (21:12 UTC)
Expired: May 15, 2018, 6:15 PM EDT
In force: 63 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Hail: 1.0 in
Wind: 70.0 mph

County Chester County, PA

The radar

The Philadelphia radar (KDIX), 120 km from the middle of the area, began a volume at 21:14 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
May 15, 5:37 PM EDT	TSTM WND DMG	1 Wnw Chesterbrook, PA	A COUPLE REPORTS OF DOWNED OR UPROOTED TREES IN VALLEY FORGE AND CHESTERBROOK. TIME APPROXIMATED BASED ON SOCIAL MEDIA POSTINGS AND RADAR.
May 15, 5:52 PM EDT	HAIL 0.75	Exton, PA

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
May 15, 1:46 PM EDT	Severe Thunderstorm Watch	SPC	9 hr

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 9.2 hours before the alert went out and 172 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: 47 J/kg
Mixed-layer CIN: -484 J/kg
Mixed-layer LCL: 1259 m above ground
0-6 km bulk shear: 21 kt
0-1 km storm-relative helicity: 117 m²/s²
0-3 km storm-relative helicity: 79 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

941 
WUUS51 KPHI 152112
SVRPHI
PAC029-152215-
/O.NEW.KPHI.SV.W.0018.180515T2112Z-180515T2215Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Mount Holly NJ
512 PM EDT TUE MAY 15 2018

The National Weather Service in Mount Holly NJ has issued a

* Severe Thunderstorm Warning for...
  Chester County in southeastern Pennsylvania...

* Until 615 PM EDT.

* At 512 PM EDT, a severe thunderstorm was located over Bareville, or
  near Akron, moving east at 55 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...
  West Chester, Coatesville, Westtown, Downingtown, Kennett Square,
  Oxford, Parkesburg, West Grove, Honey Brook, Homeville, Glen Roy,
  Cochranville, Mount Vernon, Marshallton, Lionville-Marchwood,
  Glenmoore, Paoli, Chester Springs, Lionville and Ladenberg.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3976 7606 3983 7604 3983 7602 3987 7599
      3995 7600 4004 7593 4012 7593 4015 7584
      4008 7540 4006 7540 3996 7549 3988 7559
      3984 7560 3981 7570 3972 7577 3973 7610
TIME...MOT...LOC 2112Z 277DEG 48KT 4012 7615 

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

po

1 follow-up statement

715 
WWUS51 KPHI 152158
SVSPHI

Severe Weather Statement
National Weather Service Mount Holly NJ
558 PM EDT TUE MAY 15 2018

PAC029-152215-
/O.CON.KPHI.SV.W.0018.000000T0000Z-180515T2215Z/
Chester PA-
558 PM EDT TUE MAY 15 2018

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 615 PM EDT
FOR CHESTER COUNTY...

At 556 PM EDT, a severe thunderstorm were located across the 
northern and western parts of Chester County. They were moving 
east at 55 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...
West Chester, Coatesville, Westtown, Downingtown, Kennett Square,
Oxford, Parkesburg, West Grove, Homeville, Glen Roy, Cochranville,
Mount Vernon, Marshallton, Lionville-Marchwood, Paoli, Lionville,
Ladenberg, Kemblesville, North Star and Hockessin.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3976 7606 3983 7604 3983 7602 3987 7599
      3995 7600 4004 7593 4005 7591 4008 7579
      4008 7540 4006 7540 3996 7549 3988 7559
      3984 7560 3981 7570 3972 7577 3973 7610
TIME...MOT...LOC 2156Z 277DEG 48KT 4005 7538 

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

PO

The office that day

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

Issued	Product	Office	Counties	Lasted
May 15, 3:40 AM EDT	Flash Flood Watch	PHI	Berks, Bucks, Chester, Delaware, Lehigh, Montgomery and 1 more	21 hr
May 15, 2:49 PM EDT	Special Weather Statement	PHI	Berks, Carbon, Lehigh, Monroe, Northampton	56 min
May 15, 3:20 PM EDT	Severe Thunderstorm Warning	PHI	Carbon, Monroe	55 min
May 15, 3:46 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Lehigh, Northampton	74 min
May 15, 4:12 PM EDT	Severe Thunderstorm Warning	PHI	Carbon, Monroe	33 min
May 15, 4:24 PM EDT	Special Weather Statement	PHI	Berks	51 min
May 15, 4:26 PM EDT	Tornado Warning	PHI	Berks, Bucks, Lehigh, Montgomery, Northampton	19 min
May 15, 4:41 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Bucks, Chester, Lehigh, Montgomery, Northampton	64 min
May 15, 5:14 PM EDT	Areal Flood Advisory	PHI	Berks, Chester, Montgomery	2 hr
May 15, 5:22 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Chester, Delaware, Montgomery, Philadelphia	38 min
May 15, 5:31 PM EDT	Areal Flood Advisory	PHI	Bucks, Lehigh, Montgomery	3 hr
May 15, 5:35 PM EDT	Areal Flood Advisory	PHI	Bucks, Chester, Delaware, Montgomery, Philadelphia	4 hr
May 15, 5:38 PM EDT	Severe Thunderstorm Warning	PHI	Delaware, Philadelphia	67 min
May 15, 5:53 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Chester, Delaware, Montgomery, Philadelphia	52 min
May 15, 6:10 PM EDT	Areal Flood Advisory	PHI	Philadelphia	4 hr
May 15, 6:15 PM EDT	Severe Thunderstorm Warning	PHI	Chester	60 min
May 15, 6:35 PM EDT	Severe Thunderstorm Warning	PHI	Chester	40 min
May 15, 6:58 PM EDT	Areal Flood Advisory	PHI	Chester	4 hr

Nearby

Severe Thunderstorm Warnings in Pennsylvania, 2018 Every severe thunderstorm warning in 2018

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.