Alert archive / Pennsylvania / Flash Flood Warnings in 2011

Flash Flood Warning 51, NWS Philadelphia/Mount Holly

September 7, 2011Chester County, Pennsylvania

NWS Philadelphia/Mount Holly issued this flash flood warning at Sep 7, 2011, 3:06 PM EDT for Chester County, Pennsylvania. It was in force for 4 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
Sep 7, 2011, 3:06 PM EDT (19:06 UTC)
Expired
Sep 7, 2011, 7:00 PM EDT
In force
4 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), 128 km from the middle of the area, began a volume at 19:07 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, 7.1 hours before the alert went out and 160 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 12:00Z on 2011-09-07Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1 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 12:00Z on 2011-09-07The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 154 square meters per square second.193958Sfc1 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
1 J/kg
Mixed-layer CIN
-270 J/kg
Mixed-layer LCL
448 m above ground
0-6 km bulk shear
31 kt
0-1 km storm-relative helicity
154 m²/s²
0-3 km storm-relative helicity
184 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

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

365 
WGUS51 KPHI 071906
FFWPHI
PAC029-072300-
/O.NEW.KPHI.FF.W.0051.110907T1906Z-110907T2300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
306 PM EDT WED SEP 7 2011

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

* FLASH FLOOD WARNING FOR...
  WESTERN CHESTER COUNTY...

* UNTIL 700 PM EDT...

* AT 301 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED  
  VERY HEAVY RAIN FROM A CLUSTER OF STRONG THUNDERSTORMS OVER THE 
  WESTERN PART OF THE COUNTY. THE HEAVY RAIN WILL RESULT IN FLASH 
  FLOODING.

* LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO RURAL AREAS
  OF WESTERN CHESTER COUNTY.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

PLEASE REPORT FLOODING...HAIL OR WIND DAMAGE TO THE NATIONAL WEATHER
SERVICE BY CALLING TOLL FREE...1-877-633-6772.

&&

LAT...LON 3978 7607 3985 7603 3987 7601 3992 7601
      3993 7600 3999 7599 4003 7595 4011 7595
      4013 7590 3972 7581 3972 7609 3977 7609

$$

HAYES
2 follow-up statements
190 
WGUS71 KPHI 072200
FFSPHI

FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
600 PM EDT WED SEP 7 2011

PAC029-072300-
/O.CON.KPHI.FF.W.0051.000000T0000Z-110907T2300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
CHESTER PA-
600 PM EDT WED SEP 7 2011

...A FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 700 PM EDT FOR
WESTERN CHESTER COUNTY...

RAIN HAS ENDED OVER THE AREA FOR THE TIME BEING...BUT FLOODING HAS 
BEEN REPORTED IN FLOOD-PRONE AREAS AND MAY CONTINUE A WHILE LONGER.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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.

PLEASE REPORT FLOODING...HAIL OR WIND DAMAGE BY CALLING YOUR LOCAL
LAW ENFORCEMENT OFFICIALS OR BY CALLING THE NATIONAL WEATHER SERVICE
TOLL FREE AT...1-877-633-6772.

&&

LAT...LON 3978 7607 3985 7603 3987 7601 3992 7601
      3993 7600 3999 7599 4003 7595 4011 7595
      4013 7590 3972 7581 3972 7609 3977 7609

$$

FORECASTER: AMC
233 
WGUS71 KPHI 072301
FFSPHI

FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
701 PM EDT WED SEP 7 2011

PAC029-072301-
/O.EXP.KPHI.FF.W.0051.000000T0000Z-110907T2300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
CHESTER PA-
701 PM EDT WED SEP 7 2011

...THE FLASH FLOOD WARNING WILL EXPIRE AT 700 PM EDT FOR WESTERN
CHESTER COUNTY...

THE IMMEDIATE FLASH FLOOD THREAT HAS ENDED...HOWEVER FLOODING 
CONTINUES ALONG THE WEST BRANCH OF THE BRANDYWINE CREEK.

A FLASH FLOOD WARNING REMAINS IN EFFECT FOR CENTRAL AND EASTERN 
CHESTER COUNTY UNTIL 730 PM EDT. ADDITIONAL RAINFALL AND FLOODING IS 
POSSIBLE OVERNIGHT.

LAT...LON 3978 7607 3985 7603 3987 7601 3992 7601
      3993 7600 3999 7599 4003 7595 4011 7595
      4013 7590 3972 7581 3972 7609 3977 7609

$$

FORECASTER: AMC

The office that day

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

IssuedProductOfficeCountiesLasted
Sep 6, 10:31 PM EDTAreal Flood WarningPHIBerks, Lehigh15 hr
Sep 6, 11:13 PM EDTRiver Flood WarningPHIChester, Montgomery, Philadelphia3 days
Sep 6, 11:19 PM EDTRiver Flood WarningPHIMontgomery17 hr
Sep 7, 12:59 AM EDTRiver Flood WarningPHIChester, Delaware41 hr
Sep 7, 3:40 AM EDTRiver Flood WarningPHIMontgomery, Philadelphia54 hr
Sep 7, 3:47 AM EDTRiver Flood WarningPHIDelaware4 hr
Sep 7, 4:26 AM EDTRiver Flood WarningPHIBerks, Montgomery6 hr
Sep 7, 4:26 AM EDTRiver Flood WarningPHIMontgomery3 days
Sep 7, 9:48 AM EDTRiver Flood WarningPHILehigh, Northampton5 hr
Sep 7, 10:05 AM EDTRiver Flood WarningPHIMonroe, Northampton60 hr
Sep 7, 10:05 AM EDTRiver Flood WarningPHINorthampton67 hr
Sep 7, 10:05 AM EDTRiver Flood WarningPHIBucks68 hr
Sep 7, 10:05 AM EDTRiver Flood WarningPHIBucks67 hr
Sep 7, 10:05 AM EDTRiver Flood WarningPHIBucks67 hr
Sep 7, 10:05 AM EDTRiver Flood WarningPHIBucks64 hr
Sep 7, 10:05 AM EDTRiver Flood WarningPHIBucks67 hr
Sep 7, 10:05 AM EDTRiver Flood WarningPHIBucks68 hr
Sep 7, 11:48 AM EDTCoastal Flood AdvisoryPHIDelaware, Philadelphia18 hr
Sep 7, 1:32 PM EDTSpecial Weather StatementPHIBerks58 min
Sep 7, 1:38 PM EDTSpecial Weather StatementPHILebanon52 min
Sep 7, 1:50 PM EDTAreal Flood AdvisoryPHIBerks17 min
Sep 7, 2:05 PM EDTFlash Flood WarningPHIBerks4 hr
Sep 7, 2:36 PM EDTSpecial Weather StatementPHIBerks54 min
Sep 7, 2:39 PM EDTSpecial Weather StatementPHIChester66 min
Sep 7, 3:33 PM EDTFlash Flood WarningPHIBerks, Chester4 hr
Sep 7, 3:49 PM EDTSpecial Weather StatementPHIBerks, Chester56 min
Sep 7, 4:06 PM EDTRiver Flood WarningPHIBerks, Montgomery41 hr
Sep 7, 4:06 PM EDTRiver Flood WarningPHIBerks45 hr
Sep 7, 4:09 PM EDTSpecial Weather StatementPHIBucks, Delaware, Lehigh, Montgomery, Northampton, Philadelphia66 min
Sep 7, 5:10 PM EDTAreal Flood AdvisoryPHIBerks, Bucks, Carbon, Lehigh, Monroe, Montgomery and 1 more3 hr
Sep 7, 6:07 PM EDTRiver Flood WarningPHIChester10 hr
Sep 7, 7:14 PM EDTAreal Flood AdvisoryPHIBerks65 min
Sep 7, 7:21 PM EDTAreal Flood WarningPHIBerks, Chester14 hr
Sep 7, 7:32 PM EDTSpecial Weather StatementPHIBerks58 min
Sep 7, 7:39 PM EDTCoastal Flood WarningPHIDelaware, Philadelphia6 hr

Nearby

Flash Flood Warnings in Pennsylvania, 2011Every flash flood warning in 2011

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.