Alert archive / Pennsylvania / Flash Flood Warnings in 2009

Flash Flood Warning 23, NWS Philadelphia/Mount Holly

July 31, 2009Bucks County, Chester County, Montgomery County, Pennsylvania; Cecil County, Maryland

NWS Philadelphia/Mount Holly issued this flash flood warning at Jul 31, 2009, 3:04 PM EDT for Bucks County, Chester County, Montgomery County, Pennsylvania; Cecil County, Maryland. It was in force for 3 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: Jul 31, 2009, 3:04 PM EDT (19:04 UTC)
Expired: Jul 31, 2009, 6:04 PM EDT
In force: 3 hr
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Flood severity: None

Counties Cecil County, MD, Bucks County, PA, Chester County, PA, Montgomery County, PA

The radar

The Philadelphia radar (KDIX), 104 km from the middle of the area, began a volume at 19:04 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 207 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: 276 J/kg
Mixed-layer CIN: -61 J/kg
Mixed-layer LCL: 888 m above ground
0-6 km bulk shear: 42 kt
0-1 km storm-relative helicity: -25 m²/s²
0-3 km storm-relative helicity: 18 m²/s²
Significant tornado parameter: -0.0
Supercell composite: -0.3

Open this sounding in Storm Lab

The text

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

000 
WGUS51 KPHI 311904
FFWPHI
MDC015-PAC017-029-091-312300-
/O.NEW.KPHI.FF.W.0023.090731T1904Z-090731T2300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
304 PM EDT FRI JUL 31 2009

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

* FLASH FLOOD WARNING FOR...
  NORTHWESTERN CECIL COUNTY IN NORTHEAST MARYLAND...
  NORTHWESTERN BUCKS COUNTY IN SOUTHEAST PENNSYLVANIA...
  CHESTER COUNTY IN SOUTHEAST PENNSYLVANIA...
  THIS INCLUDES THE CITY OF WEST CHESTER...
  MONTGOMERY COUNTY IN SOUTHEAST PENNSYLVANIA...

* UNTIL 700 PM EDT

* AT 258 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED   
  AN AREA OF EXCESSIVE RAINFALL OVER THE WARNED AREA.

* LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO VALLEY
  FORGE...TINICUM...SPRINGTOWN...REVERE...PUGHTOWN...PLEASANT
  VALLEY...PIPERSVILLE...OTTSVILLE...GLENMOORE...GERYVILLE...
  GARDENVILLE...FRICKS...ERWINNA...CHESTER SPRINGS...CEDARVILLE...
  BEDMINSTER...FERNDALE...SPRING MOUNT...SOUDERTON...QUAKERTOWN...
  POTTSTOWN...PHOENIXVILLE...PERKASIE...LANSDALE...HONEY BROOK...
  GILBERTSVILLE...ELVERSON...EAST GREENVILLE...DUBLIN...DOYLESTOWN...
  COLLEGEVILLE AND CHALFONT

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A FLASH FLOOD WARNING MEANS THAT FLOODING IS IMMINENT OR OCCURRING.  
DO NOT ATTEMPT TO CROSS SWIFTLY FLOWING WATERS OR WATERS OF UNKNOWN 
DEPTH BY FOOT OR BY AUTOMOBILE.

&&

LAT...LON 3973 7615 3978 7607 3987 7601 4011 7595
      4024 7570 4043 7555 4042 7549 4062 7520
      4056 7519 4056 7511 4053 7507 4042 7506
      4040 7502 4040 7498 3956 7610 3972 7624

$$

KRUZDLO

1 follow-up statement

000 
WGUS71 KPHI 312204
FFSPHI

FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
604 PM EDT FRI JUL 31 2009

MDC015-PAC017-029-091-312214-
/O.CAN.KPHI.FF.W.0023.000000T0000Z-090731T2300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
CECIL MD-CHESTER PA-MONTGOMERY PA-BUCKS PA-
604 PM EDT FRI JUL 31 2009

...THE FLASH FLOOD WARNING HAS BEEN CANCELLED FOR NORTHWESTERN
BUCKS...MONTGOMERY...CHESTER AND NORTHWESTERN CECIL COUNTIES...

A SEVERE THUNDERSTORM WATCH REMAINS IN EFFECT UNTIL 900 PM EDT FRIDAY
EVENING FOR DELAWARE AND NORTHEASTERN MARYLAND AND NEW JERSEY AND
EASTERN PENNSYLVANIA.

LAT...LON 3973 7615 3978 7607 3987 7601 4011 7595
      4024 7570 4043 7555 4042 7549 4062 7520
      4056 7519 4056 7511 4053 7507 4042 7506
      4040 7502 4040 7498 3956 7610 3972 7624

$$

KRUZDLO

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 31, 2:13 PM EDT	Flash Flood Warning	PHI	Carbon, Monroe	4 hr
Jul 31, 3:36 PM EDT	Severe Thunderstorm Warning	PHI	Chester, Delaware	54 min
Jul 31, 3:40 PM EDT	Severe Thunderstorm Warning	PHI	Chester	65 min
Jul 31, 4:03 PM EDT	Severe Thunderstorm Warning	PHI	Chester, Delaware	57 min
Jul 31, 4:08 PM EDT	Flash Flood Warning	PHI	Bucks, Chester, Delaware, Montgomery, Philadelphia	3 hr
Jul 31, 4:31 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Delaware, Montgomery, Philadelphia	59 min
Jul 31, 3:10 PM EDT	Severe Thunderstorm Warning	PHI	Cecil, Kent	65 min
Jul 31, 3:54 PM EDT	Severe Thunderstorm Warning	PHI	Caroline, Kent, Queen Anne's	53 min

Nearby

Flash Flood Warnings in Pennsylvania, 2009 Flash Flood Warnings in Maryland, 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.