Alert archive / Pennsylvania / Special Weather Statements in 2018

Special Weather Statement, NWS Philadelphia/Mount Holly

September 18, 2018Chester County, Pennsylvania

NWS Philadelphia/Mount Holly issued this special weather statement at Sep 18, 2018, 1:13 AM EDT for Chester County, Pennsylvania. It was in force for 62 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: Sep 18, 2018, 1:13 AM EDT (05:13 UTC)
Expired: Sep 18, 2018, 2:15 AM EDT
In force: 62 min
Issued by: NWS Philadelphia/Mount Holly

County Chester County, PA

The radar

The Dover AFB radar (KDOX), 128 km from the middle of the area, began a volume at 05:16 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, 5.2 hours before the alert went out and 161 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: 709 J/kg
Mixed-layer CIN: -3 J/kg
Mixed-layer LCL: 587 m above ground
0-6 km bulk shear: 31 kt
0-1 km storm-relative helicity: 178 m²/s²
0-3 km storm-relative helicity: 256 m²/s²
Significant tornado parameter: 0.5
Supercell composite: 4.8

Open this sounding in Storm Lab

The text

As transmitted.

811 
WWUS81 KPHI 180513
SPSPHI

Special Weather Statement
National Weather Service Mount Holly NJ
113 AM EDT TUE SEP 18 2018

MDZ008-PAZ060-101>103-105-180615-
Cecil-Upper Bucks-Western Montgomery-Western Chester-Eastern
Chester-Berks-
113 AM EDT TUE SEP 18 2018

...A LINE OF STRONG THUNDERSTORMS WILL AFFECT NORTHWESTERN CECIL...
EASTERN BERKS...NORTHWESTERN MONTGOMERY AND CHESTER COUNTIES...

At 110 AM EDT, radar indicated strong thunderstorms were located
along a line extending from Bechtelsville to Rising Sun. Movement was
northeast at 30 mph.

Torrential rainfall is also occurring with these storms, and may 
cause localized flooding. Do not drive your vehicle through flooded 
roadways. Rainfall amounts up to an inch or more may fall in a 
relatively short period of time. Winds up to 40 mph are possible 
with these storms.

Locations impacted include...
Calvert, Pottstown, Phoenixville, Coatesville, Downingtown,
Souderton, Birdsboro, Collegeville, Oxford, Kutztown, Royersford,
Fleetwood, Parkesburg, North East, Trappe, East Greenville, West
Grove, Rising Sun, Topton and Honey Brook.

LAT...LON 3972 7614 3974 7612 3973 7610 3976 7606
      3985 7602 3987 7599 3995 7600 4004 7593
      4011 7594 4014 7588 4021 7598 4057 7573
      4032 7530 3954 7601 3955 7603 3954 7607
      3972 7623
TIME...MOT...LOC 0510Z 222DEG 27KT 4037 7561 3972 7608 

$$

Meola

The office that day

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

Issued	Product	Office	Counties	Lasted
Sep 18, 4:13 AM EDT	Special Weather Statement	PHI	Camden, Gloucester, Salem	92 min
Sep 18, 9:27 AM EDT	Flash Flood Watch	PHI	Burlington, Camden, Gloucester, Hunterdon, Mercer, Middlesex and 5 more	6 hr
Sep 18, 10:59 AM EDT	Areal Flood Advisory	PHI	Hunterdon, Mercer, Middlesex, Monmouth, Somerset	4 hr
Sep 18, 12:01 PM EDT	Flash Flood Warning	PHI	Mercer, Middlesex, Somerset	4 hr
Sep 18, 12:16 PM EDT	Special Weather Statement	PHI	Middlesex	29 min
Sep 18, 12:36 PM EDT	Areal Flood Advisory	PHI	Burlington, Camden, Gloucester, Mercer, Middlesex, Monmouth and 2 more	3 hr
Sep 18, 1:20 PM EDT	Special Weather Statement	PHI	Burlington	25 min
Sep 18, 1:35 PM EDT	Special Marine Warning	PHI		55 min
Sep 18, 2:51 PM EDT	Special Marine Warning	PHI		38 min
Sep 18, 2:55 PM EDT	Special Weather Statement	PHI	Ocean	35 min
Sep 18, 3:02 PM EDT	Areal Flood Advisory	PHI	Burlington, Ocean	3 hr
Sep 18, 3:12 PM EDT	Areal Flood Advisory	PHI	Atlantic, Burlington, Camden, Ocean	47 min
Sep 18, 3:47 PM EDT	Special Weather Statement	PHI	Ocean	28 min
Sep 18, 4:12 PM EDT	Special Weather Statement	PHI	Atlantic	33 min
Sep 18, 4:47 PM EDT	Areal Flood Advisory	PHI	Atlantic, Cape May, Cumberland, Ocean	2 hr
Sep 18, 5:17 PM EDT	Flash Flood Warning	PHI	Atlantic	113 min
Sep 18, 2:09 AM EDT	Special Weather Statement	PHI	Chester, Delaware, Montgomery, Philadelphia	81 min
Sep 18, 2:38 AM EDT	Areal Flood Advisory	PHI	Chester, Montgomery	4 hr
Sep 18, 6:27 AM EDT	Areal Flood Advisory	PHI	Carbon, Monroe	4 hr
Sep 18, 10:57 AM EDT	Areal Flood Advisory	PHI	Bucks, Chester, Delaware, Montgomery, Philadelphia	3 hr
Sep 18, 5:26 PM EDT	Special Weather Statement	PHI	Sussex	34 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.