Alert archive / Pennsylvania / Flash Flood Watches in 2012

Flash Flood Watch 1, NWS Philadelphia/Mount Holly

May 29, 20127 counties in Pennsylvania; New Castle County, Delaware

NWS Philadelphia/Mount Holly issued this flash flood watch at May 29, 2012, 12:29 PM EDT for 7 counties in Pennsylvania; New Castle County, Delaware. It took effect at May 29, 2012, 3:00 PM EDT. It was in force for 6 hr.

The area

The counties it named.

The facts

Issued
May 29, 2012, 12:29 PM EDT (16:29 UTC)
In effect from
May 29, 2012, 3:00 PM EDT
Expired
May 29, 2012, 8:34 PM EDT
In force
6 hr
Issued by
NWS Philadelphia/Mount Holly
Flood severity
None

Counties New Castle County, DE, Berks County, PA, Carbon County, PA, Delaware County, PA, Lehigh County, PA, Monroe County, PA, Northampton County, PA, Philadelphia County, PA

The radar

The Philadelphia radar (KDIX), 106 km from the middle of the area, began a volume at 16:31 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

Phillips Aaf/Abe, MD (KAPG), launched 12:00Z, 4.5 hours before the alert went out and 116 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, Phillips Aaf/Abe, MD at 12:00Z on 2012-05-29Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 667 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Phillips Aaf/Abe, MD at 12:00Z on 2012-05-29The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -39 square meters per square second.1939Sfc1 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
667 J/kg
Mixed-layer CIN
-217 J/kg
Mixed-layer LCL
1153 m above ground
0-6 km bulk shear
6 kt
0-1 km storm-relative helicity
-39 m²/s²
0-3 km storm-relative helicity
-10 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.

024 
WGUS61 KPHI 291629
FFAPHI

URGENT - IMMEDIATE BROADCAST REQUESTED
FLOOD WATCH
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1229 PM EDT TUE MAY 29 2012

DEZ001-PAZ054-055-060>062-067>071-300030-
/O.NEW.KPHI.FF.A.0001.120529T1900Z-120530T0800Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
NEW CASTLE-CARBON-MONROE-BERKS-LEHIGH-NORTHAMPTON-CHESTER-
MONTGOMERY-BUCKS-DELAWARE-PHILADELPHIA-
INCLUDING THE CITIES OF...WILMINGTON...JIM THORPE...STROUDSBURG...
READING...ALLENTOWN...BETHLEHEM...EASTON...WEST CHESTER...
NORRISTOWN...DOYLESTOWN...MEDIA...PHILADELPHIA
1229 PM EDT TUE MAY 29 2012

...FLASH FLOOD WATCH IN EFFECT THROUGH LATE TONIGHT...

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY HAS ISSUED A

* FLASH FLOOD WATCH FOR PORTIONS OF NORTHERN DELAWARE AND 
  PENNSYLVANIA...INCLUDING THE FOLLOWING AREAS...IN NORTHERN 
  DELAWARE...NEW CASTLE. IN PENNSYLVANIA...BERKS...BUCKS... 
  CARBON...CHESTER...DELAWARE...LEHIGH...MONROE...MONTGOMERY... 
  NORTHAMPTON AND PHILADELPHIA. 

* THROUGH LATE TONIGHT

* SUMMERLIKE CONDITIONS WITH AN APPROACHING COLD FRONT WILL
  PRODUCE SEVERAL BANDS OF VERY HEAVY RAIN IN EASTERN PENNSYLVANIA
  AND NORTHERN DELAWARE...MAINLY BETWEEN 5 PM AND MIDNIGHT.

* IF 1 TO 2 INCHES OF RAIN OCCURS IN AN HOUR ON URBAN SURFACES
  FROM WILMINGTON TO PHILADELPHIA AS WELL AS IN PORTIONS OF
  MONROE...CARBON...BUCKS...LEHIGH AND BERKS COUNTIES THAT
  RECEIVED 2 TO 6 INCHES OF RAIN THIS PAST WEEKEND...FLASH
  FLOODING WOULD RESULT.
 
PRECAUTIONARY/PREPAREDNESS ACTIONS...

A FLASH FLOOD WATCH MEANS THAT CONDITIONS MAY DEVELOP THAT LEAD
TO FLASH FLOODING. FLASH FLOODING IS A VERY DANGEROUS SITUATION.

YOU SHOULD MONITOR LATER FORECASTS AND BE PREPARED TO TAKE ACTION
SHOULD FLASH FLOOD WARNINGS BE ISSUED.

&&

$$


DRAG
2 follow-up statements
760 
WGUS61 KPHI 292153
FFAPHI

FLOOD WATCH
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
553 PM EDT TUE MAY 29 2012

DEZ001-PAZ054-055-060>062-067>071-300800-
/O.CON.KPHI.FF.A.0001.000000T0000Z-120530T0800Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
NEW CASTLE-CARBON-MONROE-BERKS-LEHIGH-NORTHAMPTON-CHESTER-
MONTGOMERY-BUCKS-DELAWARE-PHILADELPHIA-
INCLUDING THE CITIES OF...WILMINGTON...JIM THORPE...STROUDSBURG...
READING...ALLENTOWN...BETHLEHEM...EASTON...WEST CHESTER...
NORRISTOWN...DOYLESTOWN...MEDIA...PHILADELPHIA
553 PM EDT TUE MAY 29 2012

...FLASH FLOOD WATCH REMAINS IN EFFECT UNTIL 4 AM EDT WEDNESDAY...

THE FLASH FLOOD WATCH CONTINUES FOR

* PORTIONS OF NORTHERN DELAWARE AND PENNSYLVANIA...INCLUDING THE 
  FOLLOWING AREAS...IN NORTHERN DELAWARE...NEW CASTLE. IN 
  PENNSYLVANIA...BERKS...BUCKS...CARBON...CHESTER...DELAWARE... 
  LEHIGH...MONROE...MONTGOMERY...NORTHAMPTON AND PHILADELPHIA. 

* UNTIL 4 AM EDT WEDNESDAY

* SUMMER-LIKE CONDITIONS THIS EVENING UNTIL A COLD FRONT WITH
  THUNDERSTORMS CROSS THE AREA. THE THUNDERSTORMS WILL PRODUCE
  BANDS OF HEAVY RAINFALL UNTIL AROUND MIDNIGHT.

* FLASH FLOODING WILL RESULT IF 1 TO 2 INCHES OF RAIN FALLS ON
  URBAN AREAS.  

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A FLASH FLOOD WATCH MEANS THAT CONDITIONS MAY DEVELOP THAT LEAD
TO FLASH FLOODING. FLASH FLOODING IS A VERY DANGEROUS SITUATION.

YOU SHOULD MONITOR LATER FORECASTS AND BE PREPARED TO TAKE ACTION
SHOULD FLASH FLOOD WARNINGS BE ISSUED.

&&

$$
396 
WGUS61 KPHI 300034
FFAPHI

FLOOD WATCH
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
834 PM EDT TUE MAY 29 2012

DEZ001-PAZ054-055-060>062-067>071-300145-
/O.CAN.KPHI.FF.A.0001.000000T0000Z-120530T0800Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
NEW CASTLE-CARBON-MONROE-BERKS-LEHIGH-NORTHAMPTON-CHESTER-
MONTGOMERY-BUCKS-DELAWARE-PHILADELPHIA-
INCLUDING THE CITIES OF...WILMINGTON...JIM THORPE...STROUDSBURG...
READING...ALLENTOWN...BETHLEHEM...EASTON...WEST CHESTER...
NORRISTOWN...DOYLESTOWN...MEDIA...PHILADELPHIA
834 PM EDT TUE MAY 29 2012

...FLASH FLOOD WATCH IS CANCELLED...

THE FLASH FLOOD WATCH FOR PORTIONS OF NORTHERN DELAWARE AND
PENNSYLVANIA HAS BEEN CANCELLED. 

THERE WILL STILL BE SHOWERS AND A FEW THUNDERSTORMS ACROSS THE
AREA FOR THE NEXT FEW HOURS. THE RAINFALL RATES ARE NO LONGER
EXPECTED TO BE GREAT ENOUGH TO CAUSE FLASH FLOODING. 


$$

The office that day

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

IssuedProductOfficeCountiesLasted
May 29, 1:36 PM EDTSpecial Weather StatementPHIMonroe54 min
May 29, 1:50 PM EDTAreal Flood AdvisoryPHICarbon, Monroe115 min
May 29, 5:06 PM EDTSpecial Weather StatementPHIBerks, Carbon, Lehigh, Monroe, Northampton114 min
May 29, 5:25 PM EDTSevere Thunderstorm WarningPHIBerks, Carbon, Lehigh95 min
May 29, 5:45 PM EDTSevere Thunderstorm WarningPHIMonroe, Northampton75 min
May 29, 6:14 PM EDTSevere Thunderstorm WarningPHIBerks, Lehigh, Northampton91 min
May 29, 6:23 PM EDTFlash Flood WarningPHICarbon, Monroe112 min
May 29, 6:44 PM EDTAreal Flood AdvisoryPHIBerks, Bucks, Lehigh, Montgomery3 hr
May 29, 6:46 PM EDTSpecial Weather StatementPHIBucks, Chester, Delaware, Montgomery, Philadelphia89 min
May 29, 6:52 PM EDTSevere Thunderstorm WarningPHIBucks, Chester, Montgomery53 min
May 29, 7:34 PM EDTSpecial Weather StatementPHIDelaware, Philadelphia56 min
May 29, 7:35 PM EDTAreal Flood AdvisoryPHIBucks, Chester, Delaware, Montgomery, Philadelphia115 min
May 29, 7:44 PM EDTSpecial Weather StatementPHIBucks61 min

Nearby

Flash Flood Watches in Pennsylvania, 2012Flash Flood Watches in Delaware, 2012Every flash flood watch in 2012

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.