Alert archive / Pennsylvania / Flash Flood Warnings in 2023

Flash Flood Warning 64, NWS Philadelphia/Mount Holly

July 16, 2023Chester County, Pennsylvania

NWS Philadelphia/Mount Holly issued this flash flood warning at Jul 16, 2023, 9:12 AM EDT for Chester County, Pennsylvania. It was in force for 2 hr. 1 report 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 16, 2023, 9:12 AM EDT (13:12 UTC)
Expired: Jul 16, 2023, 11:20 AM EDT
In force: 2 hr
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Flood severity: None

County Chester County, PA

The radar

The Philadelphia radar (KDIX), 96 km from the middle of the area, began a volume at 13:11 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 16, 9:52 AM EDT	FLOOD	West Chester, PA	Flooding on Montgomery Avenue both directions between Gay Street and Washington Street. All lanes closed.

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, 1.2 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: 275 J/kg
Mixed-layer CIN: -48 J/kg
Mixed-layer LCL: 570 m above ground
0-6 km bulk shear: 28 kt
0-1 km storm-relative helicity: 30 m²/s²
0-3 km storm-relative helicity: 97 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.2

Open this sounding in Storm Lab

The text

As transmitted.

430 
WGUS51 KPHI 161312
FFWPHI
PAC029-161715-
/O.NEW.KPHI.FF.W.0064.230716T1312Z-230716T1715Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Mount Holly NJ
912 AM EDT Sun Jul 16 2023

The National Weather Service in Mount Holly has issued a

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

* Until 115 PM EDT.

* At 912 AM EDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 1 and 2 inches of rain 
  have fallen. Additional rainfall amounts of 0.5 to 1.5 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, Westtown, Paoli, Radnor Township, West Goshen, 
  Malvern, Devon-Berwyn, and Chesterbrook.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3991 7555 3990 7563 3993 7566 3997 7566
      4003 7559 4007 7548 4006 7539 4004 7541
      3998 7546 3996 7550 3994 7552 3993 7553
      3993 7554

FLASH FLOOD...RADAR INDICATED

$$

MJL

2 follow-up statements

068 
WGUS71 KPHI 161447
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
1047 AM EDT Sun Jul 16 2023

PAC029-161715-
/O.CON.KPHI.FF.W.0064.000000T0000Z-230716T1715Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Chester PA-
1047 AM EDT Sun Jul 16 2023

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 115 PM EDT THIS 
AFTERNOON FOR NORTHEASTERN CHESTER COUNTY...

At 1047 AM EDT, Doppler radar indicated thunderstorms producing 
heavy rain across the warned area. Between 1 and 2 inches of rain 
have fallen. Additional rainfall amounts of 0.5 to 1.5 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...
  Paoli, Radnor Township, Devon-Berwyn, and Chesterbrook.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4007 7548 4006 7539 4005 7540 4004 7541
      4000 7544 4000 7545 3999 7545 3998 7546

FLASH FLOOD...RADAR INDICATED

$$

MJL

799 
WGUS71 KPHI 161520
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
1120 AM EDT Sun Jul 16 2023

PAC029-161530-
/O.CAN.KPHI.FF.W.0064.000000T0000Z-230716T1715Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Chester PA-
1120 AM EDT Sun Jul 16 2023

...FLASH FLOOD WARNING IS CANCELLED FOR NORTHEASTERN CHESTER 
COUNTY...

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 Monday for 
portions of northern Delaware...New Jersey...and Pennsylvania.

LAT...LON 4007 7548 4006 7539 4005 7540 4004 7541
      4000 7544 4000 7545 3999 7545 3998 7546

$$

MJL

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 15, 8:37 PM EDT	Areal Flood Advisory	PHI	Carbon	19 min
Jul 15, 8:44 PM EDT	Severe Thunderstorm Warning	PHI	Carbon, Monroe	30 min
Jul 15, 8:56 PM EDT	Flash Flood Warning	PHI	Carbon	95 min
Jul 16, 12:50 AM EDT	Special Weather Statement	PHI	Berks	25 min
Jul 16, 1:41 AM EDT	Special Weather Statement	PHI	Carbon, Lehigh	34 min
Jul 16, 2:12 AM EDT	Special Weather Statement	PHI	Carbon, Lehigh, Monroe	33 min
Jul 16, 2:43 AM EDT	Flash Flood Warning	PHI	Carbon, Lehigh, Monroe, Northampton	4 hr
Jul 16, 2:47 AM EDT	Special Weather Statement	PHI	Chester, Delaware	28 min
Jul 16, 3:40 AM EDT	Flash Flood Warning	PHI	Monroe, Northampton	7 hr
Jul 16, 4:05 AM EDT	Flash Flood Warning	PHI	Berks, Bucks, Chester, Lehigh, Montgomery, Northampton	6 hr
Jul 16, 4:14 AM EDT	Special Weather Statement	PHI	Bucks	31 min
Jul 16, 4:38 AM EDT	Tornado Warning	PHI	Bucks	37 min
Jul 16, 9:40 AM EDT	Flash Flood Warning	PHI	Bucks, Chester, Delaware, Montgomery, Philadelphia	3 hr
Jul 16, 9:53 AM EDT	Tornado Warning	PHI	Montgomery, Philadelphia	37 min
Jul 16, 10:54 AM EDT	Areal Flood Warning	PHI	Monroe, Northampton	5 hr
Jul 16, 11:08 AM EDT	Flash Flood Warning	PHI	Delaware, Philadelphia	3 hr
Jul 16, 12:22 PM EDT	Areal Flood Advisory	PHI	Bucks, Philadelphia	3 hr
Jul 16, 12:26 PM EDT	Areal Flood Advisory	PHI	Philadelphia	3 hr
Jul 16, 1:47 PM EDT	Areal Flood Advisory	PHI	Delaware, Philadelphia	80 min
Jul 16, 6:44 PM EDT	Areal Flood Advisory	PHI	Bucks	90 min

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.