Alert archive / Pennsylvania / Flash Flood Watches in 2009

Flash Flood Watch 4, NWS Philadelphia/Mount Holly

July 26, 20097 counties in Pennsylvania; 7 counties in New Jersey

NWS Philadelphia/Mount Holly issued this flash flood watch at Jul 26, 2009, 3:07 AM EDT for 7 counties in Pennsylvania; 7 counties in New Jersey. It took effect at Jul 26, 2009, 12:00 PM EDT. It was in force for 11 hr.

The area

The counties it named.

The facts

Issued
Jul 26, 2009, 3:07 AM EDT (07:07 UTC)
In effect from
Jul 26, 2009, 12:00 PM EDT
Expired
Jul 26, 2009, 11:02 PM EDT
In force
11 hr
Issued by
NWS Philadelphia/Mount Holly
Flood severity
None

Counties Hunterdon County, NJ, Mercer County, NJ, Middlesex County, NJ, Morris County, NJ, Somerset County, NJ, Sussex County, NJ, Warren County, NJ, 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), 93 km from the middle of the area, began a volume at 07:10 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

Brookhaven, NY (KOKX), launched 00:00Z, 7.1 hours before the alert went out and 190 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, Brookhaven, NY at 00:00Z on 2009-07-26Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 99 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, Brookhaven, NY at 00:00Z on 2009-07-26The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 139 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
99 J/kg
Mixed-layer CIN
-64 J/kg
Mixed-layer LCL
979 m above ground
0-6 km bulk shear
35 kt
0-1 km storm-relative helicity
139 m²/s²
0-3 km storm-relative helicity
158 m²/s²
Significant tornado parameter
0.0
Supercell composite
2.1

Open this sounding in Storm Lab

The text

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

000 
WGUS61 KPHI 260707
FFAPHI

URGENT - IMMEDIATE BROADCAST REQUESTED
FLOOD WATCH
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
307 AM EDT SUN JUL 26 2009

NJZ001-007>010-012-015-PAZ054-055-060>062-067>071-262100-
/O.NEW.KPHI.FF.A.0004.090726T1600Z-090727T1000Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
SUSSEX-WARREN-MORRIS-HUNTERDON-SOMERSET-MIDDLESEX-MERCER-CARBON-
MONROE-BERKS-LEHIGH-NORTHAMPTON-CHESTER-MONTGOMERY-BUCKS-DELAWARE-
PHILADELPHIA-
INCLUDING THE CITIES OF...NEWTON...WASHINGTON...MORRISTOWN...
FLEMINGTON...SOMERVILLE...NEW BRUNSWICK...TRENTON...JIM THORPE...
STROUDSBURG...READING...ALLENTOWN...BETHLEHEM...EASTON...
WEST CHESTER...NORRISTOWN...DOYLESTOWN...MEDIA...PHILADELPHIA
307 AM EDT SUN JUL 26 2009

...FLASH FLOOD WATCH IN EFFECT FROM NOON EDT TODAY THROUGH LATE
TONIGHT...

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY HAS ISSUED A

* FLASH FLOOD WATCH FOR PORTIONS OF NEW JERSEY AND 
 PENNSYLVANIA...INCLUDING THE FOLLOWING AREAS...IN NEW JERSEY...
 HUNTERDON...MERCER...MIDDLESEX...MORRIS...SOMERSET...SUSSEX 
 AND WARREN. IN PENNSYLVANIA...BERKS...BUCKS...CARBON...
 CHESTER...DELAWARE...LEHIGH...MONROE...MONTGOMERY...
 NORTHAMPTON AND PHILADELPHIA.

* FROM NOON EDT TODAY THROUGH LATE TONIGHT

* LOW PRESSURE ALOFT...A SLOWLY ADVANCING COLD FRONT...MOISTURE
  AND INSTABILITY MAY COMBINE TO GENERATE STRONG THUNDERSTORMS
  WITH HEAVY DOWNPOURS THAT COULD RESULT IN FLASH FLOODING.
  LOCALIZED RAINFALL AMOUNTS IN EXCESS OF TWO INCHES ARE POSSIBLE
  INTO TONIGHT.

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.

&&

$$

MPD
2 follow-up statements
000 
WGUS61 KPHI 261840
FFAPHI

FLOOD WATCH
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
240 PM EDT SUN JUL 26 2009

NJZ001-007>010-012-015-PAZ054-055-060>062-067>071-271000-
/O.CON.KPHI.FF.A.0004.000000T0000Z-090727T1000Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
SUSSEX-WARREN-MORRIS-HUNTERDON-SOMERSET-MIDDLESEX-MERCER-CARBON-
MONROE-BERKS-LEHIGH-NORTHAMPTON-CHESTER-MONTGOMERY-BUCKS-DELAWARE-
PHILADELPHIA-
INCLUDING THE CITIES OF...NEWTON...WASHINGTON...MORRISTOWN...
FLEMINGTON...SOMERVILLE...NEW BRUNSWICK...TRENTON...JIM THORPE...
STROUDSBURG...READING...ALLENTOWN...BETHLEHEM...EASTON...
WEST CHESTER...NORRISTOWN...DOYLESTOWN...MEDIA...PHILADELPHIA
240 PM EDT SUN JUL 26 2009

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

THE FLASH FLOOD WATCH CONTINUES FOR

* PORTIONS OF NEW JERSEY AND PENNSYLVANIA...INCLUDING THE 
  FOLLOWING AREAS...IN NEW JERSEY...HUNTERDON...MERCER...
  MIDDLESEX...MORRIS...SOMERSET...SUSSEX AND WARREN. IN 
  PENNSYLVANIA...BERKS...BUCKS...CARBON...CHESTER...DELAWARE...
  LEHIGH...MONROE...MONTGOMERY...NORTHAMPTON AND PHILADELPHIA.

* THROUGH LATE TONIGHT.

* AN ABUNDANCE OF MOISTURE SURGING NORTHWARD AHEAD OF A FRONTAL
  BOUNDARY WILL COMBINE WITH AMPLE INSTABILITY TO PRODUCE SHOWERS
  AND THUNDERSTORMS THROUGH THIS EVENING. LOCALLY VERY HEAVY
  RAINFALL IS QUITE POSSIBLE WITH SOME OF THE ACTIVITY, WHICH
  COULD RESULT IN AREAS OF FLASH FLOODING. LOCALIZED RAINFALL
  AMOUNTS IN EXCESS OF TWO INCHES ARE POSSIBLE.

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.

&&

$$

GORSE/MEOLA
000 
WGUS61 KPHI 270302
FFAPHI

FLOOD WATCH
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1102 PM EDT SUN JUL 26 2009

NJZ001-007>010-012-015-PAZ054-055-060>062-067>071-270415-
/O.CAN.KPHI.FF.A.0004.000000T0000Z-090727T1000Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
SUSSEX-WARREN-MORRIS-HUNTERDON-SOMERSET-MIDDLESEX-MERCER-CARBON-
MONROE-BERKS-LEHIGH-NORTHAMPTON-CHESTER-MONTGOMERY-BUCKS-DELAWARE-
PHILADELPHIA-
INCLUDING THE CITIES OF...NEWTON...WASHINGTON...MORRISTOWN...
FLEMINGTON...SOMERVILLE...NEW BRUNSWICK...TRENTON...JIM THORPE...
STROUDSBURG...READING...ALLENTOWN...BETHLEHEM...EASTON...
WEST CHESTER...NORRISTOWN...DOYLESTOWN...MEDIA...PHILADELPHIA
1102 PM EDT SUN JUL 26 2009

...FLASH FLOOD WATCH IS CANCELLED...

ALTHOUGH THERE MAY BE SCATTERED THUNDERSTORMS OVERNIGHT...ANY
RESULTING FLOODING SHOULD BE MINOR. THEREFORE...THE FLASH FLOOD
WATCH FOR PORTIONS OF NEW JERSEY AND PENNSYLVANIA HAS BEEN
CANCELLED. 

$$

MPD

The office that day

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

IssuedProductOfficeCountiesLasted
Jul 26, 4:06 PM EDTSevere Thunderstorm WarningPHIBucks, Lehigh, Northampton54 min
Jul 26, 7:05 PM EDTSevere Thunderstorm WarningPHIChester70 min
Jul 25, 11:08 PM EDTFlash Flood WarningPHISussex, Warren2 hr
Jul 26, 12:15 AM EDTFlash Flood WarningPHISussex90 min
Jul 26, 3:26 AM EDTSmall Craft AdvisoryPHI30 hr
Jul 26, 3:29 PM EDTSevere Thunderstorm WarningPHIMonmouth61 min
Jul 26, 3:30 PM EDTSpecial Marine WarningPHI60 min
Jul 26, 4:55 PM EDTTornado WarningPHIHunterdon, Middlesex, Morris, Somerset55 min
Jul 26, 7:07 PM EDTSevere Thunderstorm WarningPHIMiddlesex, Monmouth53 min
Jul 26, 7:40 PM EDTSevere Thunderstorm WarningPHIBurlington, Mercer, Monmouth, Ocean65 min

Nearby

Flash Flood Watches in Pennsylvania, 2009Flash Flood Watches in New Jersey, 2009Every flash flood watch 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.