Alert archive / Pennsylvania / Flash Flood Warnings in 2023

Flash Flood Warning 34, NWS Philadelphia/Mount Holly

July 8, 2023Chester County, Pennsylvania

NWS Philadelphia/Mount Holly issued this flash flood warning at Jul 8, 2023, 5:51 PM EDT for Chester County, Pennsylvania. It was in force for 4 hr. 5 reports came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued: Jul 8, 2023, 5:51 PM EDT (21:51 UTC)
Expired: Jul 8, 2023, 10:00 PM 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 Philadelphia radar (KDIX), 100 km from the middle of the area, began a volume at 21:55 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.

What was reported inside it

Time	Report	Where	Remark
Jul 8, 6:04 PM EDT	RAIN 1.22	Malvern, PA	1.22 inches of rain measured in 30 minutes ending at 6:04 PM.
Jul 8, 6:15 PM EDT	FLASH FLOOD	2 Ese West Whiteland Tw, PA	penndot camera shows multiple lanes flooded on us 202 just south of us 30.
Jul 8, 6:48 PM EDT	FLASH FLOOD	1 Se Malvern, PA	paoli pike flooded and closed between devon road and warren avenue.
Jul 8, 6:48 PM EDT	FLASH FLOOD	1 Wnw Paoli, PA	jacqueline drive at north cedar hollow road is flooded.
Jul 8, 6:50 PM EDT	FLASH FLOOD	East Whiteland Twp, PA	church road at sweetwater way is flooded.

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 9.9 hours before the alert went out and 196 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: 305 J/kg
Mixed-layer CIN: -103 J/kg
Mixed-layer LCL: 1033 m above ground
0-6 km bulk shear: 13 kt
0-1 km storm-relative helicity: -21 m²/s²
0-3 km storm-relative helicity: 44 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

514 
WGUS51 KPHI 082151
FFWPHI
PAC029-090200-
/O.NEW.KPHI.FF.W.0034.230708T2151Z-230709T0200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Mount Holly NJ
551 PM EDT Sat Jul 8 2023

The National Weather Service in Mount Holly has issued a

* Flash Flood Warning for...
  East Central Chester County in southeastern Pennsylvania...

* Until 1000 PM EDT.

* At 551 PM EDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 0.5 and 1 inch of rain 
  has 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...
  West Chester, Downingtown, Paoli, West Goshen, Malvern, and Exton.

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 4006 7550 3999 7549 3995 7557 3995 7566
      4001 7569 4004 7563

FLASH FLOOD...RADAR INDICATED

$$

MLB

3 follow-up statements

802 
WGUS71 KPHI 082228
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
628 PM EDT Sat Jul 8 2023

PAC029-090200-
/O.CON.KPHI.FF.W.0034.000000T0000Z-230709T0200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Chester PA-
628 PM EDT Sat Jul 8 2023

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 10 PM EDT THIS 
EVENING FOR EAST CENTRAL CHESTER COUNTY...

At 628 PM EDT, Doppler radar and automated rain gauges 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 
already occurring.

HAZARD...Flash flooding caused by thunderstorms.

SOURCE...Radar and automated gauges.

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...
  West Chester, Downingtown, Paoli, West Goshen, Malvern, and Exton.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4006 7550 3999 7549 3995 7557 3995 7566
      4001 7569 4004 7563

FLASH FLOOD...RADAR AND GAUGE INDICATED

$$

MLB

927 
WGUS71 KPHI 090050
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
850 PM EDT Sat Jul 8 2023

PAC029-090200-
/O.CON.KPHI.FF.W.0034.000000T0000Z-230709T0200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Chester PA-
850 PM EDT Sat Jul 8 2023

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 10 PM EDT THIS 
EVENING FOR EAST CENTRAL CHESTER COUNTY...

At 850 PM EDT, the heavy rain had exited the warned area, but 
flooding still persists. Between 1 and 3 inches of rain have fallen. 
Flash flooding is already occurring.

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...
  West Chester, Downingtown, Paoli, West Goshen, Malvern, and Exton.

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.

Be aware of your surroundings and do not drive on flooded roads.

&&

LAT...LON 4006 7550 3999 7549 3995 7557 3995 7566
      4001 7569 4004 7563

FLASH FLOOD...RADAR INDICATED

$$

MLB

324 
WGUS71 KPHI 090152
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
952 PM EDT Sat Jul 8 2023

PAC029-090202-
/O.EXP.KPHI.FF.W.0034.000000T0000Z-230709T0200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Chester PA-
952 PM EDT Sat Jul 8 2023

...FLASH FLOOD WARNING WILL EXPIRE AT 10 PM EDT THIS EVENING FOR 
EAST CENTRAL CHESTER COUNTY...

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

LAT...LON 4006 7550 3999 7549 3995 7557 3995 7566
      4001 7569 4004 7563

$$

MLB

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 8, 1:28 PM EDT	Areal Flood Advisory	PHI	Philadelphia	95 min
Jul 8, 2:05 PM EDT	Special Weather Statement	PHI	Philadelphia	25 min
Jul 8, 2:28 PM EDT	Areal Flood Advisory	PHI	Philadelphia	21 min
Jul 8, 2:40 PM EDT	Flash Flood Warning	PHI	Philadelphia	4 hr
Jul 8, 3:00 PM EDT	Special Weather Statement	PHI	Philadelphia	30 min
Jul 8, 3:17 PM EDT	Flood Watch	PHI	Berks, Bucks, Carbon, Chester, Delaware, Lehigh and 4 more	31 hr
Jul 8, 3:44 PM EDT	Special Weather Statement	PHI	Bucks	31 min
Jul 8, 3:52 PM EDT	Areal Flood Advisory	PHI	Bucks, Montgomery	3 hr
Jul 8, 4:49 PM EDT	Special Weather Statement	PHI	Delaware	26 min
Jul 8, 5:00 PM EDT	Areal Flood Advisory	PHI	Chester, Delaware, Montgomery, Philadelphia	25 min
Jul 8, 5:15 PM EDT	Flash Flood Warning	PHI	Chester, Delaware, Montgomery, Philadelphia	4 hr
Jul 8, 5:19 PM EDT	Special Weather Statement	PHI	Delaware	26 min
Jul 8, 5:30 PM EDT	Special Weather Statement	PHI	Chester	30 min
Jul 8, 5:43 PM EDT	Areal Flood Advisory	PHI	Chester	10 min
Jul 8, 6:02 PM EDT	Special Weather Statement	PHI	Montgomery	28 min
Jul 8, 6:33 PM EDT	Areal Flood Advisory	PHI	Chester, Montgomery	3 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.