Alert archive / Pennsylvania / Special Weather Statements in 2018

Special Weather Statement, NWS Philadelphia/Mount Holly

August 18, 2018Chester County, Pennsylvania

NWS Philadelphia/Mount Holly issued this special weather statement at Aug 18, 2018, 3:20 PM EDT for Chester County, Pennsylvania. It was in force for 40 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, 2018, 3:20 PM EDT (19:20 UTC)
Expired: Aug 18, 2018, 4:00 PM EDT
In force: 40 min
Issued by: NWS Philadelphia/Mount Holly

County Chester County, PA

The radar

The Dover AFB radar (KDOX), 120 km from the middle of the area, began a volume at 19:22 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 nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 7.3 hours before the alert went out and 156 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: 100 J/kg
Mixed-layer CIN: -126 J/kg
Mixed-layer LCL: 1039 m above ground
0-6 km bulk shear: 35 kt
0-1 km storm-relative helicity: 28 m²/s²
0-3 km storm-relative helicity: 88 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

823 
WWUS81 KPHI 181920
SPSPHI

Special Weather Statement
National Weather Service Mount Holly NJ
320 PM EDT SAT AUG 18 2018

MDZ008-PAZ101-102-182000-
Cecil-Western Chester-Eastern Chester-
320 PM EDT SAT AUG 18 2018

...A STRONG THUNDERSTORM WILL AFFECT NORTHEASTERN CECIL AND
SOUTHWESTERN CHESTER COUNTIES...

At 320 PM EDT, a strong thunderstorm was located over Quarryville, or
11 miles southeast of Willow Street, moving east at 25 mph.

Winds up to 45 mph are possible with this storm.

This storm will be near...
  Glen Roy around 330 PM EDT.
  Mount Vernon around 335 PM EDT.
  Oxford and Homeville around 340 PM EDT.
  Parkesburg and Cochranville around 345 PM EDT.
  West Grove around 355 PM EDT.
  Ladenberg and North Star around 400 PM EDT.

Other locations impacted by this storm include Toughkenamon, South
Coatesville, Modena, Avondale, Thorndale, Atglen and Christiana.

Torrential downpours are occurring with this storm, and may cause 
localized flooding in poor drainage areas. Do not drive your vehicle 
through flooded roadways.

Frequent cloud to ground lightning is also occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

LAT...LON 3974 7612 3973 7610 3976 7606 3981 7603
      3983 7604 3987 7599 3994 7598 3995 7600
      3999 7597 4003 7574 3979 7572 3972 7579
      3965 7582 3972 7612
TIME...MOT...LOC 1920Z 266DEG 23KT 3986 7614 

$$

JRK

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 17, 8:17 PM EDT	Severe Thunderstorm Warning	PHI	Hunterdon, Morris, Somerset, Sussex, Warren	43 min
Aug 17, 8:47 PM EDT	Severe Thunderstorm Warning	PHI	Hunterdon, Mercer, Middlesex, Morris, Somerset, Sussex	43 min
Aug 17, 8:48 PM EDT	Special Weather Statement	PHI	Sussex	27 min
Aug 17, 9:26 PM EDT	Special Weather Statement	PHI	Mercer, Middlesex, Somerset	34 min
Aug 17, 10:59 PM EDT	Areal Flood Advisory	PHI	Hunterdon, Middlesex, Morris, Somerset, Warren	75 min
Aug 17, 11:25 PM EDT	Special Weather Statement	PHI	Somerset	35 min
Aug 17, 11:30 PM EDT	Flash Flood Warning	PHI	Hunterdon, Middlesex, Morris, Somerset	4 hr
Aug 17, 11:41 PM EDT	Severe Thunderstorm Warning	PHI	Middlesex, Morris, Somerset	34 min
Aug 17, 11:52 PM EDT	Special Weather Statement	PHI	Middlesex	23 min
Aug 18, 12:56 AM EDT	Areal Flood Advisory	PHI	Gloucester, Salem	4 hr
Aug 18, 2:37 AM EDT	Special Weather Statement	PHI	Ocean	23 min
Aug 18, 2:38 AM EDT	Special Marine Warning	PHI		52 min
Aug 18, 2:41 AM EDT	Special Weather Statement	PHI	Atlantic, Cumberland	34 min
Aug 18, 2:46 AM EDT	Severe Thunderstorm Warning	PHI	Ocean	14 min
Aug 18, 3:15 AM EDT	Special Marine Warning	PHI		30 min
Aug 18, 3:16 AM EDT	Flash Flood Watch	PHI	Burlington, Camden, Gloucester, Hunterdon, Mercer, Middlesex and 7 more	20 hr
Aug 18, 3:34 PM EDT	Special Weather Statement	PHI	Sussex	41 min
Aug 18, 3:40 PM EDT	Small Craft Advisory	PHI		45 hr
Aug 18, 4:14 PM EDT	Special Weather Statement	PHI	Sussex	46 min
Aug 18, 4:33 PM EDT	Special Weather Statement	PHI	Gloucester	42 min
Aug 18, 5:16 PM EDT	Special Weather Statement	PHI	Burlington, Camden	44 min
Aug 18, 5:44 PM EDT	Areal Flood Advisory	PHI	Burlington, Camden	98 min
Aug 18, 5:55 PM EDT	Special Weather Statement	PHI	Burlington	35 min
Aug 18, 6:17 PM EDT	Severe Thunderstorm Warning	PHI	Burlington, Ocean	43 min
Aug 18, 6:31 PM EDT	Special Marine Warning	PHI		119 min
Aug 18, 6:44 PM EDT	Severe Thunderstorm Warning	PHI	Ocean	29 min
Aug 17, 8:04 PM EDT	Special Weather Statement	PHI	Monroe	41 min
Aug 17, 8:54 PM EDT	Special Weather Statement	PHI	Carbon, Monroe	36 min
Aug 18, 4:54 PM EDT	Special Weather Statement	PHI	Philadelphia	21 min

Nearby

Special Weather Statements in Pennsylvania, 2018 Every special weather statement 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; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.