Alert archive / Pennsylvania / Flash Flood Warnings in 2009

Flash Flood Warning 15, NWS Philadelphia/Mount Holly

July 28, 2009Chester County, Pennsylvania

NWS Philadelphia/Mount Holly issued this flash flood warning at Jul 28, 2009, 12:04 AM EDT for Chester County, Pennsylvania. It was in force for 53 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: Jul 28, 2009, 12:04 AM EDT (04:04 UTC)
Expired: Jul 28, 2009, 12:57 AM EDT
In force: 53 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Flood severity: None

County Chester County, PA

The radar

The Philadelphia radar (KDIX), 112 km from the middle of the area, began a volume at 04:06 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, 4.1 hours before the alert went out and 200 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: 212 J/kg
Mixed-layer CIN: -23 J/kg
Mixed-layer LCL: 1931 m above ground
0-6 km bulk shear: 19 kt
0-1 km storm-relative helicity: 3 m²/s²
0-3 km storm-relative helicity: 52 m²/s²
Significant tornado parameter: 0.0
Supercell composite: -0.1

Open this sounding in Storm Lab

The text

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

000 
WGUS51 KPHI 280404
FFWPHI
PAC029-280600-
/O.NEW.KPHI.FF.W.0015.090728T0404Z-090728T0600Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1204 AM EDT TUE JUL 28 2009

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

* FLASH FLOOD WARNING FOR...
  NORTH CENTRAL CHESTER COUNTY IN SOUTHEAST PENNSYLVANIA...

* UNTIL 200 AM EDT

* AT 1202 AM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
  THE STRONG POSSIBILITY OF FLASH FLOODING FROM A THUNDERSTORM OVER
  THE WARNED AREA. RADAR HAS ESTIMATED THAT IN EXCESS OF THREE INCHES
  OF RAIN HAS FALLEN SINCE 900 PM AND THAT ADDITIONAL RAINFALL IN
  EXCESS OF ONE-HALF INCH IS POSSIBLE. 

* LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO CEDARVILLE
  AND AREAS AROUND FRENCH CREEK. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

BE ESPECIALLY CAUTIOUS AT NIGHT WHEN IT IS HARDER TO RECOGNIZE THE
DANGERS OF FLOODING. IF FLASH FLOODING IS OBSERVED ACT QUICKLY. MOVE
UP TO HIGHER GROUND TO ESCAPE FLOOD WATERS. DO NOT STAY IN AREAS
SUBJECT TO FLOODING WHEN WATER BEGINS RISING.

DO NOT DRIVE YOUR VEHICLE INTO AREAS WHERE THE WATER COVERS THE
ROADWAY. THE WATER DEPTH MAY BE TOO GREAT TO ALLOW YOUR CAR TO CROSS
SAFELY. MOVE TO HIGHER GROUND.

&&

LAT...LON 4016 7587 4025 7570 4026 7566 4023 7562
      4023 7561 4022 7559 4020 7559 4020 7557
      4016 7553 4000 7578 4003 7595

$$

MPD

1 follow-up statement

000 
WGUS71 KPHI 280457
FFSPHI

FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1257 AM EDT TUE JUL 28 2009

PAC029-280507-
/O.CAN.KPHI.FF.W.0015.000000T0000Z-090728T0600Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
CHESTER PA-
1257 AM EDT TUE JUL 28 2009

...THE FLASH FLOOD WARNING HAS BEEN CANCELLED FOR NORTH CENTRAL
CHESTER COUNTY...

THUNDERSTORMS HAVE DISSIPATED AND THE THREAT OF FLASH FLOODING HAS 
ENDED. 

LAT...LON 4016 7587 4025 7570 4026 7566 4023 7562
      4023 7561 4022 7559 4020 7559 4020 7557
      4016 7553 4000 7578 4003 7595

$$

MPD

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 27, 9:05 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Chester, Montgomery	55 min
Jul 27, 9:46 PM EDT	Areal Flood Advisory	PHI	Berks, Chester	3 hr
Jul 28, 7:18 AM EDT	Areal Flood Warning	PHI	Chester, Montgomery	2 hr

Nearby

Flash Flood Warnings in Pennsylvania, 2009 Every flash flood warning in 2009

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.