Alert archive / Pennsylvania / Special Weather Statements in 2017

Special Weather Statement, NWS Philadelphia/Mount Holly

April 29, 20175 counties in Pennsylvania

NWS Philadelphia/Mount Holly issued this special weather statement at Apr 29, 2017, 3:51 AM EDT for 5 counties in Pennsylvania. It was in force for 39 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
Apr 29, 2017, 3:51 AM EDT (07:51 UTC)
Expired
Apr 29, 2017, 4:30 AM EDT
In force
39 min
Issued by
NWS Philadelphia/Mount Holly

Counties Berks County, PA, Bucks County, PA, Chester County, PA, Delaware County, PA, Montgomery County, PA

The radar

The Philadelphia radar (KDIX), 123 km from the middle of the area, began a volume at 07:54 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 00:00Z, 7.9 hours before the alert went out and 180 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-pSkew-T log-p diagram, Washington/Dulle, VA at 00:00Z on 2017-04-29Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 145 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Washington/Dulle, VA at 00:00Z on 2017-04-29The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 157 square meters per square second.19395878Sfc1 km3 km6 km9 kmRMLM
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
145 J/kg
Mixed-layer CIN
-140 J/kg
Mixed-layer LCL
1741 m above ground
0-6 km bulk shear
63 kt
0-1 km storm-relative helicity
157 m²/s²
0-3 km storm-relative helicity
318 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.1

Open this sounding in Storm Lab

The text

As transmitted.

720 
WWUS81 KPHI 290751
SPSPHI

Special Weather Statement
National Weather Service Mount Holly NJ
351 AM EDT SAT APR 29 2017

DEZ001-NJZ009-010-015-017-PAZ060-061-070-071-101>106-290830-
New Castle-Mercer-Hunterdon-Somerset-Gloucester-Lower
Bucks-Lehigh-Eastern Montgomery-Western Chester-Philadelphia-Upper
Bucks-Western Montgomery-Delaware-Eastern Chester-Berks-
351 AM EDT SAT APR 29 2017

...A LINE OF STRONG THUNDERSTORMS WILL AFFECT NORTH CENTRAL NEW
CASTLE...SOUTHEASTERN HUNTERDON...NORTHWESTERN MERCER...NORTHWESTERN
GLOUCESTER...SOUTHWESTERN SOMERSET...SOUTHEASTERN BERKS...
MONTGOMERY...SOUTHEASTERN LEHIGH...BUCKS...CHESTER...NORTHWESTERN
PHILADELPHIA AND DELAWARE COUNTIES...

At 351 AM EDT, radar indicated strong thunderstorms were located
along a line extending from near Laureldale to near Quarryville.
Movement was east at 60 mph.

Winds in excess of 40 mph and pea size hail are possible with these
storms.

Locations impacted include...
Philadelphia, Reading, West Chester, Norristown, Chester, Pottstown,
Phoenixville, Lansdale, West Norriton, East Norriton, Coatesville,
Yeadon, Westtown, Wyomissing, Quakertown, Perkasie, Doylestown,
Byram, Downingtown and Conshohocken.

Torrential rainfall is also occurring with these storms, and may
cause localized flooding. Do not drive your vehicle through flooded
roadways.

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

LAT...LON 3985 7602 3987 7599 3992 7600 3994 7598
      3995 7600 4004 7593 4011 7594 4014 7588
      4024 7603 4047 7590 4054 7475 3983 7534
      3980 7605
TIME...MOT...LOC 0751Z 269DEG 52KT 4036 7585 3986 7617 

$$

SFJ

The office that day

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

IssuedProductOfficeCountiesLasted
Apr 29, 2:54 AM EDTSpecial Weather StatementPHIBurlington36 min
Apr 29, 4:14 AM EDTSpecial Weather StatementPHIHunterdon, Middlesex, Somerset46 min
Apr 29, 4:20 AM EDTSevere Thunderstorm WarningPHIBurlington, Hunterdon, Mercer, Middlesex, Monmouth, Somerset40 min
Apr 29, 4:22 AM EDTSpecial Weather StatementPHIBurlington, Camden, Gloucester38 min
Apr 29, 4:29 AM EDTAreal Flood AdvisoryPHIHunterdon, Mercer, Middlesex, Morris, Somerset4 hr
Apr 29, 4:32 AM EDTSevere Thunderstorm WarningPHIHunterdon, Mercer, Middlesex, Monmouth, Morris, Somerset43 min
Apr 29, 4:56 AM EDTSpecial Marine WarningPHI64 min
Apr 29, 4:56 AM EDTSpecial Weather StatementPHIBurlington, Mercer, Monmouth, Ocean49 min
Apr 29, 5:16 AM EDTSpecial Marine WarningPHI29 min
Apr 29, 6:16 AM EDTSpecial Marine WarningPHI29 min
Apr 29, 7:04 AM EDTAreal Flood WarningPHIHunterdon, Somerset4 hr
Apr 29, 3:12 AM EDTAreal Flood AdvisoryPHIBerks4 hr
Apr 29, 3:20 AM EDTSpecial Weather StatementPHIBerks, Lehigh, Northampton40 min
Apr 29, 2:57 AM EDTSpecial Weather StatementPHIQueen Anne's48 min
Apr 29, 3:39 AM EDTSpecial Weather StatementPHICaroline36 min

Nearby

Special Weather Statements in Pennsylvania, 2017Every special weather statement 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.