Alert archive / Pennsylvania / Flood Watches in 2011

Flood Watch 15, NWS Philadelphia/Mount Holly

December 26, 2011Delaware County, Philadelphia County, Pennsylvania; New Castle County, Delaware

NWS Philadelphia/Mount Holly issued this flood watch at Dec 26, 2011, 3:13 PM EST for Delaware County, Philadelphia County, Pennsylvania; New Castle County, Delaware. It took effect at Dec 27, 2011, 3:00 PM EST. It was in force for 6 hr.

The area

The counties it named.

The facts

Issued
Dec 26, 2011, 3:13 PM EST (20:13 UTC)
In effect from
Dec 27, 2011, 3:00 PM EST
Expired
Dec 27, 2011, 8:51 PM EST
In force
6 hr
Issued by
NWS Philadelphia/Mount Holly
Flood severity
None

Counties New Castle County, DE, Delaware County, PA, Philadelphia County, PA

The radar

The Philadelphia radar (KDIX), 85 km from the middle of the area, began a volume at 20:13 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, 8.2 hours before the alert went out and 199 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 2011-12-26Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 3 joules per kilogram.LCLEL10008507005003002001001 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, Washington/Dulle, VA at 12:00Z on 2011-12-26The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 104 square meters per square second.1939587897117136Sfc1 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
3 J/kg
Mixed-layer CIN
-4 J/kg
Mixed-layer LCL
1291 m above ground
0-6 km bulk shear
84 kt
0-1 km storm-relative helicity
104 m²/s²
0-3 km storm-relative helicity
213 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.

172 
WGUS61 KPHI 262013
FFAPHI

URGENT - IMMEDIATE BROADCAST REQUESTED
FLOOD WATCH
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
313 PM EST MON DEC 26 2011
 
DEZ001-PAZ067>071-271000-
/O.NEW.KPHI.FA.A.0015.111227T2000Z-111228T0500Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
NEW CASTLE-CHESTER-MONTGOMERY-BUCKS-DELAWARE-PHILADELPHIA-
INCLUDING THE CITIES OF...WILMINGTON...WEST CHESTER...
NORRISTOWN...DOYLESTOWN...MEDIA...PHILADELPHIA
313 PM EST MON DEC 26 2011

...FLOOD WATCH IN EFFECT FROM TUESDAY AFTERNOON THROUGH TUESDAY
EVENING...

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY HAS ISSUED A

* FLOOD WATCH FOR PORTIONS OF NORTHERN DELAWARE AND SOUTHEAST 
  PENNSYLVANIA...INCLUDING THE FOLLOWING AREAS...IN NORTHERN 
  DELAWARE...NEW CASTLE. IN SOUTHEAST PENNSYLVANIA...BUCKS... 
  CHESTER...DELAWARE...MONTGOMERY AND PHILADELPHIA. 

* FROM TUESDAY AFTERNOON THROUGH TUESDAY EVENING

* HEAVIER RAIN IS EXPECTED TO FALL TUESDAY AFTERNOON INTO EVENING
  IN THE WATCH AREA. EVENT RAINFALL TOTALS OF 1.0 TO 1.5 INCHES WOULD
  BE ENOUGH TO START FLOODING OF THE MORE SUSCEPTIBLE CREEKS AND
  SMALL RIVERS IN THE WATCH AREA.

* POOR DRAINAGE ROADWAY FLOODING SHOULD BE EXPECTED. MAINLY MINOR
  CREEK AND SMALLER RIVER FLOODING IS POSSIBLE. THIS MAY CLOSE
  SOME ROADWAYS IN THE WATCH AREA. THE HEAVIER RAIN SHOULD HAVE AN
  IMPACT ON THE EVENING COMMUTE EVEN IF ITS LIGHTER THAN AVERAGE
  BECAUSE OF THE HOLIDAY WEEK.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A FLOOD WATCH MEANS THERE IS A POTENTIAL FOR FLOODING BASED ON
CURRENT FORECASTS.

YOU SHOULD MONITOR LATER FORECASTS AND BE ALERT FOR POSSIBLE
FLOOD WARNINGS. THOSE LIVING IN AREAS PRONE TO FLOODING SHOULD BE
PREPARED TO TAKE ACTION SHOULD FLOODING DEVELOP.

&&

$$

TFG
3 follow-up statements
722 
WGUS61 KPHI 270838
FFAPHI

FLOOD WATCH
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
338 AM EST TUE DEC 27 2011

DEZ001-PAZ067>071-272200-
/O.CON.KPHI.FA.A.0015.111227T2000Z-111228T0500Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
NEW CASTLE-CHESTER-MONTGOMERY-BUCKS-DELAWARE-PHILADELPHIA-
INCLUDING THE CITIES OF...WILMINGTON...WEST CHESTER...
NORRISTOWN...DOYLESTOWN...MEDIA...PHILADELPHIA
338 AM EST TUE DEC 27 2011

...FLOOD WATCH REMAINS IN EFFECT FROM 3 PM EST THIS AFTERNOON
THROUGH THIS EVENING...

THE FLOOD WATCH CONTINUES FOR

* PORTIONS OF NORTHERN DELAWARE AND SOUTHEAST PENNSYLVANIA... 
  INCLUDING THE FOLLOWING AREAS...IN NORTHERN DELAWARE...NEW 
  CASTLE. IN SOUTHEAST PENNSYLVANIA...BUCKS...CHESTER... 
  DELAWARE...MONTGOMERY AND PHILADELPHIA. 

* FROM 3 PM EST THIS AFTERNOON THROUGH THIS EVENING

* HEAVIER RAIN IS EXPECTED TO FALL THIS AFTERNOON INTO THIS
  EVENING IN THE WATCH AREA. EVENT RAINFALL TOTALS OF 1.0 TO 1.5
  INCHES WOULD BE ENOUGH TO START FLOODING OF THE MORE SUSCEPTIBLE
  CREEKS AND SMALL RIVERS IN THE WATCH AREA.

* POOR DRAINAGE ROADWAY FLOODING SHOULD BE EXPECTED. MAINLY 
  MINOR CREEK AND SMALLER RIVER FLOODING IS POSSIBLE. THIS MAY 
  CLOSE SOME ROADWAYS IN THE WATCH AREA. THE HEAVIER RAIN SHOULD 
  HAVE AN IMPACT ON THE EVENING COMMUTE EVEN IF ITS LIGHTER THAN 
  AVERAGE BECAUSE OF THE HOLIDAY WEEK. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A FLOOD WATCH MEANS THERE IS A POTENTIAL FOR FLOODING BASED ON
CURRENT FORECASTS.

YOU SHOULD MONITOR LATER FORECASTS AND BE ALERT FOR POSSIBLE
FLOOD WARNINGS. THOSE LIVING IN AREAS PRONE TO FLOODING SHOULD BE
PREPARED TO TAKE ACTION SHOULD FLOODING DEVELOP.

&&

$$
238 
WGUS61 KPHI 271926
FFAPHI

FLOOD WATCH
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
226 PM EST TUE DEC 27 2011

DEZ001-PAZ067>071-280500-
/O.CON.KPHI.FA.A.0015.111227T2000Z-111228T0500Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
NEW CASTLE-CHESTER-MONTGOMERY-BUCKS-DELAWARE-PHILADELPHIA-
INCLUDING THE CITIES OF...WILMINGTON...WEST CHESTER...
NORRISTOWN...DOYLESTOWN...MEDIA...PHILADELPHIA
226 PM EST TUE DEC 27 2011

...FLOOD WATCH REMAINS IN EFFECT UNTIL MIDNIGHT EST TONIGHT...

THE FLOOD WATCH CONTINUES FOR

* PORTIONS OF NORTHERN DELAWARE AND SOUTHEAST PENNSYLVANIA... 
  INCLUDING THE FOLLOWING AREAS...IN NORTHERN DELAWARE...NEW 
  CASTLE. IN SOUTHEAST PENNSYLVANIA...BUCKS...CHESTER... 
  DELAWARE...MONTGOMERY AND PHILADELPHIA. 

* UNTIL MIDNIGHT EST TONIGHT

* HEAVIER RAIN IS EXPECTED TO FALL THROUGH THE EVENING IN THE WATCH
  AREA. EVENT RAINFALL TOTALS OF 1.0 TO 1.5 INCHES WOULD BE ENOUGH
  TO START FLOODING OF THE MORE SUSCEPTIBLE CREEKS AND SMALL
  RIVERS IN THE WATCH AREA.

* POOR DRAINAGE ROADWAY FLOODING SHOULD BE EXPECTED. MAINLY MINOR
  CREEK AND SMALLER RIVER FLOODING IS POSSIBLE. THIS MAY CLOSE
  SOME ROADWAYS IN THE WATCH AREA. THE HEAVIER RAIN SHOULD HAVE AN
  IMPACT ON THE EVENING COMMUTE EVEN THOUGH IT IS LIGHTER THAN
  AVERAGE BECAUSE OF THE HOLIDAY WEEK.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A FLOOD WATCH MEANS THERE IS A POTENTIAL FOR FLOODING BASED ON
CURRENT FORECASTS.

YOU SHOULD MONITOR LATER FORECASTS AND BE ALERT FOR POSSIBLE
FLOOD WARNINGS. THOSE LIVING IN AREAS PRONE TO FLOODING SHOULD BE
PREPARED TO TAKE ACTION SHOULD FLOODING DEVELOP.

&&

$$
093 
WGUS61 KPHI 280151
FFAPHI

FLOOD WATCH
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
851 PM EST TUE DEC 27 2011
 
DEZ001-PAZ067>071-280300-
/O.CAN.KPHI.FA.A.0015.000000T0000Z-111228T0500Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
NEW CASTLE-CHESTER-MONTGOMERY-BUCKS-DELAWARE-PHILADELPHIA-
INCLUDING THE CITIES OF...WILMINGTON...WEST CHESTER...
NORRISTOWN...DOYLESTOWN...MEDIA...PHILADELPHIA
851 PM EST TUE DEC 27 2011

...FLOOD WATCH IS CANCELLED...

NO ADDITIONAL FLOOD WARNINGS ARE ANTICIPATED AND THE HEAVY RAIN IS
OVER.

THE PERKIOMEN CREEK IN EAST GREENVILLE IN MONTGOMERY COUNTY AND
THE CHRISTINA RIVER AT COOCHS BRIDGE IN NEW CASTLE COUNTY ARE
EXPECTED TO CREST CLOSE TO FLOOD STAGE LATER THIS EVENING.

$$

Nearby

Flood Watches in Pennsylvania, 2011Flood Watches in Delaware, 2011Every flood watch 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.