Alert archive / Maryland / Severe Thunderstorm Warnings in 2017

Severe Thunderstorm Warning 165, NWS Philadelphia/Mount Holly

August 18, 2017Cecil County, Kent County, Maryland; New Castle County, Delaware; Chester County, Pennsylvania

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Aug 18, 2017, 5:03 PM EDT for Cecil County, Kent County, Maryland; New Castle County, Delaware; Chester County, 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 18, 2017, 5:03 PM EDT (21:03 UTC)
Expired: Aug 18, 2017, 5:45 PM EDT
In force: 42 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Hail: 1.0 in
Wind: 60.0 mph

Counties New Castle County, DE, Cecil County, MD, Kent County, MD, Chester County, PA

The radar

The Dover AFB radar (KDOX), 94 km from the middle of the area, began a volume at 21:05 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 18, 5:40 PM EDT	TSTM WND DMG	New Garden, PA	SEVERAL TREES DOWN.

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

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 9.1 hours before the alert went out and 142 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.

287 
WUUS51 KPHI 182103
SVRPHI
DEC003-MDC015-029-PAC029-182145-
/O.NEW.KPHI.SV.W.0165.170818T2103Z-170818T2145Z/

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

The National Weather Service in Mount Holly NJ has issued a

* Severe Thunderstorm Warning for...
  Northern New Castle County in northern Delaware...
  North central Kent County in northeastern Maryland...
  Cecil County in northeastern Maryland...
  Southwestern Chester County in southeastern Pennsylvania...

* Until 545 PM EDT

* At 502 PM EDT, severe thunderstorms were located along a line
  extending from Quarryville to near Cockeysville, moving east at 30
  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...
  Wilmington, Newark, Elkton, Calvert, Pennsville, Elsmere, Kennett
  Square, New Castle, Oxford, North East, West Grove, Rising Sun,
  Delaware City, Charlestown, Newport, Cecilton, Arden, Betterton,
  Glen Roy and Blake.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

In addition to large hail and damaging winds...frequent cloud to
ground lightning is occurring with this storm. Move indoors
immediately. Remember...if you can hear thunder...you are close
enough to be struck by lightning.

&&

LAT...LON 3973 7610 3987 7599 3989 7599 3982 7545
      3980 7541 3977 7546 3961 7556 3926 7604
      3931 7619 3934 7616 3933 7614 3937 7611
      3937 7606 3942 7600 3946 7601 3952 7598
      3955 7603 3955 7608 3972 7623
TIME...MOT...LOC 2102Z 286DEG 28KT 3987 7616 3955 7662 

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

SFJ

1 follow-up statement

679 
WWUS51 KPHI 182133
SVSPHI

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

DEC003-MDC015-029-PAC029-182145-
/O.CON.KPHI.SV.W.0165.000000T0000Z-170818T2145Z/
New Castle DE-Kent MD-Cecil MD-Chester PA-
533 PM EDT FRI AUG 18 2017

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 545 PM EDT
FOR NORTHERN NEW CASTLE...NORTH CENTRAL KENT...CECIL AND SOUTHWESTERN
CHESTER COUNTIES...

At 532 PM EDT, severe thunderstorms were located along a line
extending from near West Grove to Bel Air South, moving east at 30
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...
Wilmington, Newark, Elkton, Calvert, Pennsville, Elsmere, Kennett
Square, New Castle, Oxford, North East, West Grove, Rising Sun,
Delaware City, Charlestown, Newport, Cecilton, Arden, Betterton, Glen
Roy and Blake.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

To report severe weather contact your nearest law enforcement agency.
They will send your report to the National Weather Service office in
Mount Holly NJ.

In addition to large hail and damaging winds...frequent cloud to
ground lightning is occurring with this storm. Move indoors
immediately. Remember...if you can hear thunder...you are close
enough to be struck by lightning.

&&

LAT...LON 3973 7610 3987 7599 3989 7599 3982 7545
      3980 7541 3977 7546 3961 7556 3926 7604
      3931 7619 3934 7616 3933 7614 3937 7611
      3937 7606 3942 7600 3946 7601 3952 7598
      3955 7603 3955 7608 3972 7623
TIME...MOT...LOC 2132Z 286DEG 28KT 3981 7589 3949 7635 

HAIL...1.00IN
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	Caroline, Cecil, Kent, Queen Anne's, Talbot	18 hr
Aug 18, 4:29 PM EDT	Severe Thunderstorm Warning	PHI	Cecil	61 min
Aug 18, 4:57 PM EDT	Areal Flood Advisory	PHI	Cecil	3 hr
Aug 18, 5:39 PM EDT	Severe Thunderstorm Warning	PHI	Cecil, Kent	66 min
Aug 18, 6:10 PM EDT	Severe Thunderstorm Warning	PHI	Caroline, Kent, Queen Anne's, Talbot	65 min
Aug 18, 6:12 PM EDT	Areal Flood Advisory	PHI	Cecil, Kent, Queen Anne's	3 hr
Aug 18, 7:07 PM EDT	Severe Thunderstorm Warning	PHI	Caroline, Kent, Queen Anne's, Talbot	53 min
Aug 18, 7:33 PM EDT	Areal Flood Advisory	PHI	Caroline, Talbot	3 hr
Aug 18, 7:53 PM EDT	Severe Thunderstorm Warning	PHI	Caroline, Kent, Queen Anne's, Talbot	48 min
Aug 18, 5:20 PM EDT	Areal Flood Advisory	PHI	New Castle	3 hr
Aug 18, 6:20 PM EDT	Special Weather Statement	PHI	Sussex	25 min
Aug 18, 6:38 PM EDT	Special Weather Statement	PHI	New Castle	37 min
Aug 18, 6:48 PM EDT	Special Weather Statement	PHI	New Castle	27 min
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, 4:24 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Bucks, Montgomery	51 min
Aug 18, 5:11 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Chester, Delaware, Montgomery, Philadelphia	49 min
Aug 18, 5:54 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Montgomery, Philadelphia	66 min

Nearby

Severe Thunderstorm Warnings in Maryland, 2017 Severe Thunderstorm Warnings in Delaware, 2017 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.