Alert archive / Pennsylvania / Flash Flood Warnings in 2023

Flash Flood Warning 25, NWS Philadelphia/Mount Holly

July 3, 2023Chester County, Pennsylvania

NWS Philadelphia/Mount Holly issued this flash flood warning at Jul 3, 2023, 8:39 PM EDT for Chester County, Pennsylvania. It was in force for 5 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 3, 2023, 8:39 PM EDT (00:39 UTC)
Expired: Jul 4, 2023, 2:00 AM EDT
In force: 5 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), 118 km from the middle of the area, began a volume at 00:40 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 00:00Z, 0.7 hours before the alert went out and 154 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: 1174 J/kg
Mixed-layer CIN: -26 J/kg
Mixed-layer LCL: 1237 m above ground
0-6 km bulk shear: 32 kt
0-1 km storm-relative helicity: 66 m²/s²
0-3 km storm-relative helicity: 55 m²/s²
Significant tornado parameter: 0.2
Supercell composite: 1.6

Open this sounding in Storm Lab

The text

As transmitted.

886 
WGUS51 KPHI 040039
FFWPHI
PAC029-040330-
/O.NEW.KPHI.FF.W.0025.230704T0039Z-230704T0330Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Mount Holly NJ
839 PM EDT Mon Jul 3 2023

The National Weather Service in Mount Holly has issued a

* Flash Flood Warning for...
  Southwestern Chester County in southeastern Pennsylvania...

* Until 1130 PM EDT.

* At 839 PM EDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 0.5 and 1.5 inches of 
  rain have fallen. Additional rainfall amounts up to 1 inch are 
  possible in the warned area. Flash flooding is ongoing or expected 
  to begin shortly.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Radar.

  IMPACT...Flooding of small creeks and streams, urban areas,
           highways, streets, and underpasses as well as other
           drainage and low lying areas.

* Some locations that may experience flash flooding include...
  Kennett Square, Oxford, West Grove, Kemblesville, Cochranville, 
  Landenberg, Homeville, North Star, Mount Vernon, Glen Roy, 
  Hockessin, and Avondale.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around...don't drown when encountering flooded roads. Most 
flood deaths occur in vehicles.

Motorists should not attempt to drive around barricades or drive 
cars through flooded areas.

&&

LAT...LON 3989 7599 3993 7574 3984 7566 3977 7574
      3972 7578 3972 7614 3973 7612 3974 7611
      3973 7611 3973 7609 3974 7610 3976 7606
      3980 7604 3980 7605 3981 7603 3983 7604
      3983 7602 3985 7602 3985 7601 3987 7599

FLASH FLOOD...RADAR INDICATED

$$

AKL

3 follow-up statements

304 
WGUS51 KPHI 040154
FFWPHI
PAC029-040400-
/O.EXT.KPHI.FF.W.0025.000000T0000Z-230704T0400Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Mount Holly NJ
954 PM EDT Mon Jul 3 2023

The National Weather Service in Mount Holly has extended the

* Flash Flood Warning for...
  Southwestern Chester County in southeastern Pennsylvania...

* Until midnight EDT.

* At 954 PM EDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 1 and 2.5 inches of 
  rain have fallen. Additional rainfall amounts up to 0.5 inches are 
  possible in the warned area. Flash flooding is ongoing or expected 
  to begin shortly.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Radar.

  IMPACT...Flooding of small creeks and streams, urban areas,
           highways, streets, and underpasses as well as other
           drainage and low lying areas.

* Some locations that may experience flash flooding include...
  Kennett Square, Oxford, West Grove, Kemblesville, Cochranville, 
  Landenberg, Homeville, North Star, Mount Vernon, Glen Roy, 
  Hockessin, and Avondale.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around...don't drown when encountering flooded roads. Most 
flood deaths occur in vehicles.

Be especially cautious at night when it is harder to recognize the 
dangers of flooding.

&&

LAT...LON 3989 7599 3993 7574 3984 7566 3977 7574
      3972 7578 3972 7614 3973 7612 3974 7611
      3973 7611 3973 7609 3974 7610 3976 7606
      3980 7604 3980 7605 3981 7603 3983 7604
      3983 7602 3985 7602 3985 7601 3987 7599

FLASH FLOOD...RADAR INDICATED

$$

AKL

660 
WGUS51 KPHI 040342
FFWPHI
PAC029-040600-
/O.EXT.KPHI.FF.W.0025.000000T0000Z-230704T0600Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Mount Holly NJ
1142 PM EDT Mon Jul 3 2023

The National Weather Service in Mount Holly has extended the

* Flash Flood Warning for...
  Southwestern Chester County in southeastern Pennsylvania...

* Until 200 AM EDT.

* At 1142 PM EDT, Doppler radar indicated thunderstorms have 
  produced heavy rain across the warned area. Between 1.5 and 2.5 
  inches of rain have fallen. Flash flooding is ongoing or expected 
  to begin shortly.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Radar.

  IMPACT...Flooding of small creeks and streams, urban areas,
           highways, streets, and underpasses as well as other
           drainage and low lying areas.

* Some locations that may experience flash flooding include...
  Kennett Square, Oxford, West Grove, Kemblesville, Cochranville, 
  Landenberg, Homeville, North Star, Mount Vernon, Glen Roy, 
  Hockessin, and Avondale.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around...don't drown when encountering flooded roads. Most 
flood deaths occur in vehicles.

Motorists should not attempt to drive around barricades or drive 
cars through flooded areas.

Be especially cautious at night when it is harder to recognize the 
dangers of flooding.

Please report observed flooding to local emergency services or law 
enforcement and request they pass this information to the National 
Weather Service when you can do so safely.

&&

LAT...LON 3989 7599 3993 7574 3984 7566 3977 7574
      3972 7578 3972 7614 3973 7612 3974 7611
      3973 7611 3973 7609 3974 7610 3976 7606
      3980 7604 3980 7605 3981 7603 3983 7604
      3983 7602 3985 7602 3985 7601 3987 7599

FLASH FLOOD...RADAR INDICATED

$$

MPS

610 
WGUS71 KPHI 040551
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
151 AM EDT Tue Jul 4 2023

PAC029-040601-
/O.EXP.KPHI.FF.W.0025.000000T0000Z-230704T0600Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Chester PA-
151 AM EDT Tue Jul 4 2023

...FLASH FLOOD WARNING WILL EXPIRE AT 2 AM EDT EARLY THIS MORNING 
FOR SOUTHWESTERN CHESTER COUNTY...

The heavy rain has ended. Flooding is no longer expected to pose a 
threat.

LAT...LON 3989 7599 3993 7574 3984 7566 3977 7574
      3972 7578 3972 7614 3973 7612 3974 7611
      3973 7611 3973 7609 3974 7610 3976 7606
      3980 7604 3980 7605 3981 7603 3983 7604
      3983 7602 3985 7602 3985 7601 3987 7599

$$

MPS

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 3, 8:04 PM EDT	Areal Flood Advisory	PHI	Chester	35 min
Jul 3, 8:04 PM EDT	Severe Thunderstorm Warning	PHI	Chester, Delaware	41 min
Jul 3, 8:41 PM EDT	Severe Thunderstorm Warning	PHI	Chester, Delaware	49 min
Jul 3, 9:07 PM EDT	Flash Flood Warning	PHI	Chester	5 hr
Jul 4, 4:59 PM EDT	Severe Thunderstorm Warning	PHI	Philadelphia	46 min
Jul 4, 6:30 PM EDT	Areal Flood Advisory	PHI	Philadelphia	3 hr
Jul 4, 6:53 PM EDT	Special Weather Statement	PHI	Delaware	37 min
Jul 4, 7:05 PM EDT	Areal Flood Advisory	PHI	Delaware, Philadelphia	2 hr

Nearby

Flash Flood Warnings in Pennsylvania, 2023 Every flash flood warning in 2023

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.