Alert archive / Pennsylvania / Flash Flood Warnings in 2024

Flash Flood Warning 9, NWS Philadelphia/Mount Holly

June 29, 2024Chester County, Pennsylvania

NWS Philadelphia/Mount Holly issued this flash flood warning at Jun 29, 2024, 10:23 PM EDT for Chester County, Pennsylvania. It was in force for 4 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: Jun 29, 2024, 10:23 PM EDT (02:23 UTC)
Expired: Jun 30, 2024, 2:30 AM EDT
In force: 4 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), 120 km from the middle of the area, began a volume at 02:22 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, 2.4 hours before the alert went out and 152 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: 1561 J/kg
Mixed-layer CIN: -72 J/kg
Mixed-layer LCL: 1687 m above ground
0-6 km bulk shear: 30 kt
0-1 km storm-relative helicity: 116 m²/s²
0-3 km storm-relative helicity: 189 m²/s²
Significant tornado parameter: 0.3
Supercell composite: 4.9

Open this sounding in Storm Lab

The text

As transmitted.

955 
WGUS51 KPHI 300223
FFWPHI
PAC029-300630-
/O.NEW.KPHI.FF.W.0009.240630T0223Z-240630T0630Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Mount Holly NJ
1023 PM EDT Sat Jun 29 2024

The National Weather Service in Mount Holly has issued a

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

* Until 230 AM EDT.

* At 1023 PM EDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 1 and 3 inches of rain 
  have fallen. Additional rainfall amounts of 1 to 2 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...
  Oxford, West Grove, Cochranville, Homeville, Mount Vernon and Glen 
  Roy.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3974 7610 3975 7610 3975 7609 3976 7608
      3976 7606 3977 7606 3980 7604 3981 7603
      3982 7603 3983 7602 3985 7602 3985 7601
      3987 7600 3987 7599 3990 7599 3989 7578
      3976 7582

FLASH FLOOD...RADAR INDICATED

$$

RCM

2 follow-up statements

545 
WGUS71 KPHI 300432
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
1232 AM EDT Sun Jun 30 2024

PAC029-300630-
/O.CON.KPHI.FF.W.0009.000000T0000Z-240630T0630Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Chester PA-
1232 AM EDT Sun Jun 30 2024

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 230 AM EDT EARLY THIS 
MORNING FOR SOUTHWESTERN CHESTER COUNTY...

At 1232 AM EDT, Doppler radar indicated thunderstorms producing 
heavy rain across the warned area. Between 1 and 3 inches of rain 
have fallen. Additional rainfall amounts of 1 to 2 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...
  Oxford, West Grove, Cochranville, Homeville, Mount Vernon and Glen 
  Roy.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3974 7610 3975 7610 3975 7609 3976 7608
      3976 7606 3977 7606 3980 7604 3981 7603
      3982 7603 3983 7602 3985 7602 3985 7601
      3987 7600 3987 7599 3990 7599 3989 7578
      3976 7582

FLASH FLOOD...RADAR INDICATED

$$

RCM

164 
WGUS71 KPHI 300626
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
226 AM EDT Sun Jun 30 2024

PAC029-300636-
/O.EXP.KPHI.FF.W.0009.000000T0000Z-240630T0630Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Chester PA-
226 AM EDT Sun Jun 30 2024

...FLASH FLOOD WARNING WILL EXPIRE AT 230 AM EDT EARLY THIS MORNING 
FOR SOUTHWESTERN CHESTER COUNTY...

Light to moderate rain continues across the warned area but the 
heaviest rain has ended. Therefore, flooding is no longer expected 
to pose a threat and the Flash Flood Warning will be allowed to 
expire. Please continue to heed remaining road closures.

&&

LAT...LON 3974 7610 3975 7610 3975 7609 3976 7608
      3976 7606 3977 7606 3980 7604 3981 7603
      3982 7603 3983 7602 3985 7602 3985 7601
      3987 7600 3987 7599 3990 7599 3989 7578
      3976 7582

$$

AKL

The office that day

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

Issued	Product	Office	Counties	Lasted
Jun 29, 8:22 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Montgomery	53 min
Jun 30, 1:18 PM EDT	Severe Thunderstorm Warning	PHI	Carbon, Monroe	42 min
Jun 30, 1:57 PM EDT	Severe Thunderstorm Warning	PHI	Monroe	48 min
Jun 30, 2:10 PM EDT	Severe Thunderstorm Warning	PHI	Monroe, Northampton	50 min
Jun 30, 2:42 PM EDT	Severe Thunderstorm Warning	PHI	Northampton	63 min
Jun 30, 2:45 PM EDT	Severe Thunderstorm Warning	PHI	Carbon, Lehigh, Monroe, Northampton	45 min
Jun 30, 3:01 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Chester, Montgomery	59 min
Jun 30, 3:26 PM EDT	Severe Thunderstorm Warning	PHI	Northampton	49 min
Jun 30, 3:46 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Bucks, Lehigh, Montgomery	44 min
Jun 30, 3:52 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Chester, Delaware, Montgomery	38 min
Jun 30, 4:25 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Chester, Delaware, Montgomery, Philadelphia	50 min
Jun 30, 4:37 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Lehigh, Northampton	53 min
Jun 30, 4:54 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Chester, Montgomery	51 min
Jun 30, 5:19 PM EDT	Flash Flood Warning	PHI	Chester, Delaware, Philadelphia	3 hr
Jun 30, 5:20 PM EDT	Severe Thunderstorm Warning	PHI	Chester, Delaware	40 min
Jun 30, 5:51 PM EDT	Severe Thunderstorm Warning	PHI	Delaware, Philadelphia	39 min
Jun 30, 5:54 PM EDT	Flash Flood Warning	PHI	Delaware, Philadelphia	3 hr
Jun 30, 7:31 PM EDT	Severe Thunderstorm Warning	PHI	Chester	44 min

Nearby

Flash Flood Warnings in Pennsylvania, 2024 Every flash flood warning in 2024

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.