Alert archive / Pennsylvania / Flash Flood Warnings in 2008

Flash Flood Warning 21, NWS Philadelphia/Mount Holly

July 27, 2008Chester County, Pennsylvania

NWS Philadelphia/Mount Holly issued this flash flood warning at Jul 27, 2008, 1:34 PM EDT for Chester County, Pennsylvania. It was in force for 3 hr. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued: Jul 27, 2008, 1:34 PM EDT (17:34 UTC)
Expired: Jul 27, 2008, 4:55 PM EDT
In force: 3 hr
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Flood severity: None

County Chester County, PA

The radar

The Dover AFB radar (KDOX), 119 km from the middle of the area, began a volume at 17:35 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, 5.6 hours before the alert went out and 157 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: 1356 J/kg
Mixed-layer CIN: -70 J/kg
Mixed-layer LCL: 1062 m above ground
0-6 km bulk shear: 32 kt
0-1 km storm-relative helicity: -17 m²/s²
0-3 km storm-relative helicity: 63 m²/s²
Significant tornado parameter: 0.1
Supercell composite: 1.3

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

000 
WGUS51 KPHI 271736
FFWPHI
PAC029-272130-
/O.NEW.KPHI.FF.W.0021.080727T1734Z-080727T2130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
134 PM EDT SUN JUL 27 2008

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

* FLASH FLOOD WARNING FOR...
  SOUTHERN CHESTER COUNTY IN SOUTHEAST PENNSYLVANIA...

* UNTIL 530 PM EDT

* AT 132 PM...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED FLASH
  FLOODING MAY BE OCCURRING FROM THUNDERSTORMS OVER THE WARNED AREA.
  UP TO TWO AND A HALF TO THREE INCHES OF RAIN HAVE ALREADY FALLEN
  IN THE WARNED AREA BASED ON RADAR ESTIMATES.  AN ADDITIONAL INCH OR
  TWO OF RAIN IS EXPECTED.

* LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO GLEN ROY...
  MOUNT VERNON...LADENBERG...HOMEVILLE...COCHRANVILLE...WEST GROVE...
  OXFORD AND KENNETT SQUARE

OCTARARO CREEK MAY BEGIN TO FLOOD DUE TO THE HEAVY RAIN.

MOST FLOOD DEATHS OCCUR IN AUTOMOBILES. NEVER DRIVE YOUR VEHICLE INTO
AREAS WHERE THE WATER COVERS THE ROADWAY. FLOOD WATERS ARE USUALLY
DEEPER THAN THEY APPEAR. JUST ONE FOOT OF FLOWING WATER IS POWERFUL
ENOUGH TO SWEEP VEHICLES OFF THE ROAD. WHEN ENCOUNTERING FLOODED
ROADS MAKE THE SMART CHOICE...TURN AROUND...DONT DROWN.

LAT...LON 3977 7609 3978 7607 3983 7604 3985 7604
      3988 7600 3990 7601 3990 7600 3989 7563
      3979 7573 3973 7578 3973 7611

$$

IOVINO

1 follow-up statement

000 
WGUS71 KPHI 272055
FFSPHI

FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
455 PM EDT SUN JUL 27 2008

PAC029-272105-
/O.CAN.KPHI.FF.W.0021.000000T0000Z-080727T2130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
CHESTER PA-
455 PM EDT SUN JUL 27 2008

...THE FLASH FLOOD WARNING HAS BEEN CANCELLED FOR SOUTHWESTERN
CHESTER COUNTY...

THE HEAVY RAIN HAS MOVED WELL AWAY FROM THE AREA...AND MOST OF THE 
FLOODING HAS RECEDED.

A SEVERE THUNDERSTORM WATCH REMAINS IN EFFECT UNTIL 800 PM EDT SUNDAY
EVENING FOR DELAWARE AND NORTHEASTERN MARYLAND AND NEW JERSEY.

LAT...LON 3977 7609 3978 7607 3983 7604 3985 7604
      3988 7600 3990 7601 3990 7600 3989 7563
      3979 7573 3973 7578 3973 7611

$$

IOVINO

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 27, 11:50 AM EDT	Severe Thunderstorm Warning	PHI	Berks, Carbon, Lehigh, Monroe, Northampton	70 min
Jul 27, 12:07 PM EDT	Severe Thunderstorm Warning	PHI	Chester	53 min
Jul 27, 12:19 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Chester, Lehigh, Montgomery	56 min
Jul 27, 12:25 PM EDT	Areal Flood Advisory	PHI	Berks, Bucks, Chester, Lehigh, Montgomery	3 hr
Jul 27, 12:38 PM EDT	Severe Thunderstorm Warning	PHI	Chester	67 min
Jul 27, 12:50 PM EDT	Areal Flood Advisory	PHI	Bucks, Chester, Montgomery	3 hr
Jul 27, 12:57 PM EDT	Severe Thunderstorm Warning	PHI	Chester	63 min
Jul 27, 1:00 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Montgomery	60 min
Jul 27, 1:44 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Montgomery	61 min
Jul 27, 2:11 PM EDT	Severe Thunderstorm Warning	PHI	Bucks	64 min
Jul 27, 2:14 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Philadelphia	61 min
Jul 27, 2:17 PM EDT	Severe Thunderstorm Warning	PHI	Delaware, Philadelphia	58 min
Jul 27, 2:30 PM EDT	Areal Flood Advisory	PHI	Bucks	2 hr
Jul 27, 5:04 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Chester	56 min
Jul 27, 6:44 PM EDT	Areal Flood Advisory	PHI	Chester	72 min

Nearby

Flash Flood Warnings in Pennsylvania, 2008 Every flash flood warning in 2008

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.