Alert archive / Pennsylvania / Flash Flood Warnings in 2023

Flash Flood Warning 35, NWS Philadelphia/Mount Holly

July 9, 2023Chester County, Delaware County, Montgomery County, Pennsylvania

NWS Philadelphia/Mount Holly issued this flash flood warning at Jul 9, 2023, 11:33 AM EDT for Chester County, Delaware County, Montgomery County, Pennsylvania. It was in force for 8 hr. 12 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 9, 2023, 11:33 AM EDT (15:33 UTC)
Expired: Jul 9, 2023, 7:30 PM EDT
In force: 8 hr
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Flood severity: None

Counties Chester County, PA, Delaware County, PA, Montgomery County, PA

The radar

The Philadelphia radar (KDIX), 88 km from the middle of the area, began a volume at 15:36 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 9, 11:54 AM EDT	FLASH FLOOD	Wayne, PA	Several photos of cars floating in parking lot with water covering up past tires.
Jul 9, 12:15 PM EDT	FLASH FLOOD	1 W West Conshohocken, PA	Report of a couple vehicles stuck in flood waters near the intersection of Portland Rd and Balligomingo Rd. Time estimated via radar.
Jul 9, 12:17 PM EDT	FLASH FLOOD	2 Se King Of Prussia, PA	Live traffic camera video of Significant flooding on I-76 eastbound at Mile Post: 329.0 (Weadley Road).
Jul 9, 12:27 PM EDT	FLASH FLOOD	Wayne, PA	Reports of several cars stuck in water in and around Radnor Township. Time estimated via radar.
Jul 9, 12:52 PM EDT	FLASH FLOOD	1 Wsw West Conshohocken, PA	Live traffic video of I-476 @ EXIT 16 (I-76 PHILADELPHIA/VALLEY FORGE) on-ramp with water covering roadway.
Jul 9, 1:00 PM EDT	FLASH FLOOD	2 Wsw Newtown Twp, PA	The Crum Creek gauge and Newtown Square reached minor flood stage.
Jul 9, 1:01 PM EDT	FLOOD	1 Wnw Villanova, PA	Received video of lanes covered in flood water on I-476 SB just after Exit 13 near Villanova. Road is still passable in two lanes.
Jul 9, 1:26 PM EDT	FLOOD	1 Ese Berwyn, PA	Received several photos of street flooding in Devon.
Jul 9, 2:14 PM EDT	FLASH FLOOD	1 Wnw Wayne, PA	Social media video of Gulph Creek out of its banks and flooding nearby yards along Plant Ave near Pennsylvania Ave.
Jul 9, 4:36 PM EDT	FLOOD	Downington, PA	Report of minor street flooding at intersection of Rte 322 and Lancaster Ave. Time estimated.
Jul 9, 5:32 PM EDT	FLOOD	1 Nnw Uwchlan Twp, PA	Trained spotter measures water in Pine Creek area at 4.1 feet and rushing. Measured with a crest gauge that was in place. Water started to flood into parking area at time of report. Flooding now into yards and basements.
Jul 9, 5:38 PM EDT	FLOOD	1 Wsw Chester Springs, PA	Report of flooding near Pickering Creek in West Pikeland Twp.

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, 3.6 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: 952 J/kg
Mixed-layer CIN: -58 J/kg
Mixed-layer LCL: 686 m above ground
0-6 km bulk shear: 20 kt
0-1 km storm-relative helicity: 12 m²/s²
0-3 km storm-relative helicity: 37 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.2

Open this sounding in Storm Lab

The text

As transmitted.

215 
WGUS51 KPHI 091533
FFWPHI
PAC029-045-091-091930-
/O.NEW.KPHI.FF.W.0035.230709T1533Z-230709T1930Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Mount Holly NJ
1133 AM EDT Sun Jul 9 2023

The National Weather Service in Mount Holly has issued a

* Flash Flood Warning for...
  Northeastern Chester County in southeastern Pennsylvania...
  Northeastern Delaware County in southeastern Pennsylvania...
  South Central Montgomery County in southeastern Pennsylvania...

* Until 330 PM EDT.

* At 1133 AM 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 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...
  Norristown, Phoenixville, West Norriton, Downingtown, 
  Conshohocken, Narberth, Paoli, Valley Forge, Newtown Square, King 
  Of Prussia, and Radnor Township.

This includes the following highways...
	Pennsylvania Turnpike between mile markers 310 and 333.
	Interstate 76 in Pennsylvania between mile markers 327 and 335.
	Interstate 476 in Pennsylvania between mile markers 5 and 19.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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

&&

LAT...LON 4000 7572 4015 7571 4014 7555 4012 7528
      4004 7526 3998 7527 3998 7528 3997 7528
      3992 7529

FLASH FLOOD...RADAR INDICATED

$$

Hoeflich

5 follow-up statements

887 
WGUS71 KPHI 091606
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
1206 PM EDT Sun Jul 9 2023

PAC029-045-091-091930-
/O.CON.KPHI.FF.W.0035.000000T0000Z-230709T1930Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Chester PA-Delaware PA-Montgomery PA-
1206 PM EDT Sun Jul 9 2023

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 330 PM EDT THIS 
AFTERNOON FOR NORTHEASTERN CHESTER, NORTHEASTERN DELAWARE, AND SOUTH 
CENTRAL MONTGOMERY COUNTIES...

At 1206 PM EDT, the public reported thunderstorms producing heavy 
rain. At 12:00 PM, photos were received of high water around Wayne, 
PA. Street flooding was also reported near Berwyn, PA. Between 1 and 
2 inches of rain have fallen. Additional rainfall amounts of 1 to 2 
inches are possible in the warned area. Flash flooding is already 
occurring.

HAZARD...Life threatening flash flooding caused by thunderstorms.

SOURCE...Public reported.

IMPACT...Life threatening flash flooding of creeks and streams,
         urban areas, highways, streets, and underpasses.

Some locations that may experience flash flooding include...
Norristown, Phoenixville, West Norriton, Downingtown, Conshohocken, 
Narberth, Paoli, Valley Forge, Newtown Square, King Of Prussia, and 
Radnor Township.

This includes the following highways...
	Pennsylvania Turnpike between mile markers 310 and 333.
	Interstate 76 in Pennsylvania between mile markers 327 and 335.
	Interstate 476 in Pennsylvania between mile markers 5 and 19.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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

&&

LAT...LON 4000 7572 4015 7571 4014 7555 4012 7528
      4004 7526 3998 7527 3998 7528 3997 7528
      3992 7529

FLASH FLOOD...OBSERVED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE

$$

Hoeflich

270 
WGUS71 KPHI 091648
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
1248 PM EDT Sun Jul 9 2023

PAC029-045-091-091930-
/O.CON.KPHI.FF.W.0035.000000T0000Z-230709T1930Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Chester PA-Delaware PA-Montgomery PA-
1248 PM EDT Sun Jul 9 2023

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 330 PM EDT THIS 
AFTERNOON FOR EAST CENTRAL CHESTER, NORTHEASTERN DELAWARE, AND SOUTH 
CENTRAL MONTGOMERY COUNTIES...

At 1248 PM EDT, local law enforcement reported thunderstorms 
producing heavy raim. PennDOT reported the Schuylkill Expressway was 
closed between exit 328 and exit 330 due to flash flooding. Between 
2 and 3 inches of rain have fallen. Additional rainfall amounts of 
0.5 to 1.5 inches are possible in the warned area. Flash flooding is 
already occurring.

HAZARD...Life threatening flash flooding caused by thunderstorms.

SOURCE...Law enforcement reported.

IMPACT...Life threatening flash flooding of creeks and streams,
         urban areas, highways, streets, and underpasses.

Some locations that may experience flash flooding include...
 Norristown, Phoenixville, West Norriton, Conshohocken, Narberth, 
Radnor Township, Newtown Square, Trout Lake, King Of Prussia, 
Broomall, and Bryn Mawr.

This includes the following highways...
	Pennsylvania Turnpike between mile markers 321 and 333.
	Interstate 76 in Pennsylvania between mile markers 327 and 335.
	Interstate 476 in Pennsylvania between mile markers 5 and 19.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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

&&

LAT...LON 3996 7551 4012 7552 4014 7552 4012 7528
      4005 7526 4004 7526 3998 7527 3998 7528
      3997 7528 3992 7529

FLASH FLOOD...OBSERVED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE

$$

Hoeflich

185 
WGUS51 KPHI 091822
FFWPHI
PAC029-045-091-092130-
/O.EXT.KPHI.FF.W.0035.000000T0000Z-230709T2130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Mount Holly NJ
222 PM EDT Sun Jul 9 2023

The National Weather Service in Mount Holly has extended the

* Flash Flood Warning for...
  East Central Chester County in southeastern Pennsylvania...
  Northeastern Delaware County in southeastern Pennsylvania...
  South Central Montgomery County in southeastern Pennsylvania...

* Until 530 PM EDT.

* At 222 PM EDT, gauge reports indicated thunderstorms producing 
  heavy rain.  At 1:00 PM EDT, the Crum Creek gauge in Newtown 
  Square reached minor flood stage. Between 2.5 and 4 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...Life threatening flash flooding caused by
           thunderstorms.

  SOURCE...Gauges reported.

  IMPACT...Life threatening flash flooding of creeks and streams,
           urban areas, highways, streets, and underpasses.

* Some locations that may experience flash flooding include...
  Norristown, Phoenixville, West Norriton, Conshohocken, Narberth, 
  Radnor Township, Newtown Square, Trout Lake, King Of Prussia, 
  Broomall, and Bryn Mawr.

This includes the following highways...
	Pennsylvania Turnpike between mile markers 321 and 333.
	Interstate 76 in Pennsylvania between mile markers 327 and 335.
	Interstate 476 in Pennsylvania between mile markers 5 and 19.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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

&&

LAT...LON 3996 7551 4012 7552 4014 7552 4012 7528
      4005 7526 4004 7526 3998 7527 3998 7528
      3997 7528 3992 7529

FLASH FLOOD...GAUGE INDICATED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE

$$

Hoeflich

126 
WGUS51 KPHI 092054
FFWPHI
PAC029-045-091-092330-
/O.EXT.KPHI.FF.W.0035.000000T0000Z-230709T2330Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Mount Holly NJ
454 PM EDT Sun Jul 9 2023

The National Weather Service in Mount Holly has extended the

* Flash Flood Warning for...
  East Central Chester County in southeastern Pennsylvania...
  Northeastern Delaware County in southeastern Pennsylvania...
  South Central Montgomery County in southeastern Pennsylvania...

* Until 730 PM EDT.

* At 454 PM EDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 2.5 and 4 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...Life threatening flash flooding caused by
           thunderstorms.

  SOURCE...Radar.

  IMPACT...Life threatening flash flooding of creeks and streams,
           urban areas, highways, streets, and underpasses.

* Some locations that may experience flash flooding include...
  Philadelphia, Norristown, Phoenixville, West Norriton, 
  Conshohocken, Narberth, Radnor Township, Newtown Square, Trout 
  Lake, King Of Prussia, Broomall, and Bryn Mawr.

This includes the following highways...
	Pennsylvania Turnpike between mile markers 321 and 333.
	Interstate 76 in Pennsylvania between mile markers 327 and 335.
	Interstate 476 in Pennsylvania between mile markers 5 and 19.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3996 7551 4012 7552 4014 7552 4012 7528
      4005 7526 4004 7526 3998 7527 3998 7528
      3997 7528 3992 7529

FLASH FLOOD...RADAR INDICATED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE

$$

Hoeflich

763 
WGUS71 KPHI 092320
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
720 PM EDT Sun Jul 9 2023

PAC029-045-091-092330-
/O.EXP.KPHI.FF.W.0035.000000T0000Z-230709T2330Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Chester PA-Delaware PA-Montgomery PA-
720 PM EDT Sun Jul 9 2023

...FLASH FLOOD WARNING WILL EXPIRE AT 730 PM EDT THIS EVENING FOR 
EAST CENTRAL CHESTER, NORTHEASTERN DELAWARE, AND SOUTH CENTRAL 
MONTGOMERY COUNTIES...

Flood waters have receded. The heavy rain has ended. Flooding is no 
longer expected to pose a threat.

A Flood Watch remains in effect until 1200 AM EDT for portions of 
east central Pennsylvania...northeast Pennsylvania...and southeast 
Pennsylvania.

A Flood Watch remains in effect until 1200 AM EDT for portions of 
northern Delaware...northeast Maryland...southern New Jersey...and 
southeast Pennsylvania.

LAT...LON 3996 7551 4012 7552 4014 7552 4012 7528
      4005 7526 4004 7526 3998 7527 3998 7528
      3997 7528 3992 7529

$$

Hoeflich

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 9, 11:00 AM EDT	Special Weather Statement	PHI	Carbon	30 min
Jul 9, 11:47 AM EDT	Special Weather Statement	PHI	Monroe	43 min
Jul 9, 11:49 AM EDT	Special Weather Statement	PHI	Montgomery	41 min
Jul 9, 11:54 AM EDT	Areal Flood Advisory	PHI	Berks, Bucks, Lehigh, Montgomery	33 min
Jul 9, 12:14 PM EDT	Special Weather Statement	PHI	Bucks	46 min
Jul 9, 12:15 PM EDT	Special Weather Statement	PHI	Monroe	30 min
Jul 9, 12:22 PM EDT	Special Weather Statement	PHI	Lebanon	38 min
Jul 9, 12:27 PM EDT	Flash Flood Warning	PHI	Berks, Bucks, Lehigh, Montgomery	8 hr
Jul 9, 12:37 PM EDT	Areal Flood Advisory	PHI	Bucks, Lehigh, Northampton	2 hr
Jul 9, 12:43 PM EDT	Areal Flood Advisory	PHI	Berks	33 min
Jul 9, 12:51 PM EDT	Special Weather Statement	PHI	Northampton	24 min
Jul 9, 12:57 PM EDT	Areal Flood Advisory	PHI	Carbon, Monroe	6 hr
Jul 9, 1:02 PM EDT	Flash Flood Warning	PHI	Bucks, Lehigh, Northampton	8 hr
Jul 9, 1:16 PM EDT	Flash Flood Warning	PHI	Berks	6 hr
Jul 9, 1:17 PM EDT	Special Weather Statement	PHI	Berks	28 min
Jul 9, 1:32 PM EDT	Areal Flood Advisory	PHI	Carbon, Lehigh, Monroe, Northampton	4 hr
Jul 9, 2:16 PM EDT	Areal Flood Advisory	PHI	Berks, Lehigh	30 min
Jul 9, 2:41 PM EDT	Flash Flood Warning	PHI	Berks	4 hr
Jul 9, 2:46 PM EDT	Flash Flood Warning	PHI	Berks, Lehigh, Northampton	6 hr
Jul 9, 3:01 PM EDT	Special Weather Statement	PHI	Berks	29 min
Jul 9, 3:03 PM EDT	Special Weather Statement	PHI	Chester	27 min
Jul 9, 3:15 PM EDT	Severe Thunderstorm Warning	PHI	Berks	30 min
Jul 9, 3:20 PM EDT	Special Weather Statement	PHI	Berks	25 min
Jul 9, 3:27 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Chester	33 min
Jul 9, 3:41 PM EDT	Special Weather Statement	PHI	Berks	34 min
Jul 9, 3:51 PM EDT	Flash Flood Warning Considerable damage threat	PHI	Berks, Chester, Lehigh, Montgomery	6 hr
Jul 9, 3:59 PM EDT	Special Weather Statement	PHI	Chester	31 min
Jul 9, 4:03 PM EDT	Severe Thunderstorm Warning	PHI	Montgomery	27 min
Jul 9, 4:19 PM EDT	Special Weather Statement	PHI	Chester	26 min
Jul 9, 4:31 PM EDT	Flash Flood Warning	PHI	Chester, Montgomery	4 hr
Jul 9, 5:10 PM EDT	Severe Thunderstorm Warning	PHI	Delaware	50 min
Jul 9, 5:12 PM EDT	Flash Flood Warning	PHI	Bucks, Montgomery	5 hr
Jul 9, 5:15 PM EDT	Special Weather Statement	PHI	Bucks, Delaware, Philadelphia	30 min
Jul 9, 5:31 PM EDT	Flash Flood Warning	PHI	Chester, Delaware, Montgomery, Philadelphia	4 hr
Jul 9, 5:35 PM EDT	Severe Thunderstorm Warning	PHI	Philadelphia	25 min
Jul 9, 5:59 PM EDT	Flash Flood Warning	PHI	Bucks, Montgomery	4 hr
Jul 9, 6:05 PM EDT	Special Weather Statement	PHI	Bucks	25 min
Jul 9, 7:04 PM EDT	Areal Flood Warning	PHI	Berks	9 hr
Jul 9, 7:11 PM EDT	Areal Flood Advisory	PHI	Bucks	3 hr
Jul 9, 7:27 PM EDT	River Flood Warning	PHI	Chester	4 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.