Alert archive / Pennsylvania / Flash Flood Warnings in 2019

Flash Flood Warning 38, NWS Philadelphia/Mount Holly

July 4, 2019Chester County, Pennsylvania

NWS Philadelphia/Mount Holly issued this flash flood warning at Jul 4, 2019, 4:28 PM EDT for Chester County, Pennsylvania. It was in force for 2 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 4, 2019, 4:28 PM EDT (20:28 UTC)
Expired: Jul 4, 2019, 6:49 PM 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 Dover AFB radar (KDOX), 123 km from the middle of the area, began a volume at 20:27 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 12:00Z, 8.5 hours before the alert went out and 160 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: 494 J/kg
Mixed-layer CIN: -76 J/kg
Mixed-layer LCL: 1204 m above ground
0-6 km bulk shear: 10 kt
0-1 km storm-relative helicity: 6 m²/s²
0-3 km storm-relative helicity: 59 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

764 
WGUS51 KPHI 042028
FFWPHI
PAC029-050030-
/O.NEW.KPHI.FF.W.0038.190704T2028Z-190705T0030Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Mount Holly NJ
428 PM EDT Thu Jul 4 2019

The National Weather Service in Mount Holly NJ has issued a

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

* Until 830 PM EDT.

* At 427 PM EDT, Doppler radar indicated thunderstorms producing
  heavy rain across the warned area. Up to two inches of rain have
  already fallen. Flash flooding is expected to begin shortly in the
  areas of heaviest rain.

* Some locations that could experience flooding include...
  Coatesville, Downingtown, Kennett Square, Oxford, Parkesburg, West
  Grove, Homeville, Glen Roy, Cochranville, Mount Vernon,
  Marshallton, Ladenberg, Kemblesville, Atglen, South Coatesville,
  Avondale, Modena, Thorndale and Toughkenamon.

These storms are moving slowly and redeveloping over the same area. 
Additional rainfall amounts of one to two inches are possible in the 
warned area.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Move to higher ground now. Act quickly to protect your life.

Please report flooding to your local law enforcement agency when you
can do so safely.

A Flash Flood Warning means that flooding is imminent or occurring.
If you are in the warned area move to higher ground immediately.
Residents living along streams and creeks should take immediate
precautions to protect life and property.

&&

LAT...LON 3981 7603 3983 7604 3983 7602 3987 7601
      3987 7599 3990 7599 4005 7593 3998 7561
      3974 7579 3976 7606

$$

MPS

1 follow-up statement

361 
WGUS71 KPHI 042249
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
649 PM EDT Thu Jul 4 2019

PAC029-042258-
/O.CAN.KPHI.FF.W.0038.000000T0000Z-190705T0030Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Chester PA-
649 PM EDT Thu Jul 4 2019

...THE FLASH FLOOD WARNING FOR SOUTHWESTERN CHESTER COUNTY IS
CANCELLED...

The heavy rain has ended. Flooding is no longer expected to pose a
threat. Please continue to heed any remaining road closures.

LAT...LON 3981 7603 3983 7604 3983 7602 3987 7601
      3987 7599 3990 7599 4005 7593 3998 7561
      3974 7579 3976 7606

$$

MPS

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 4, 3:26 PM EDT	Special Weather Statement	PHI	Chester	49 min
Jul 4, 4:53 PM EDT	Special Weather Statement	PHI	Delaware	37 min
Jul 4, 5:18 PM EDT	Areal Flood Advisory	PHI	Chester, Delaware, Montgomery, Philadelphia	32 min
Jul 4, 5:42 PM EDT	Areal Flood Advisory	PHI	Berks, Chester, Montgomery	2 hr
Jul 4, 5:49 PM EDT	Flash Flood Warning	PHI	Chester, Delaware, Montgomery, Philadelphia	115 min

Nearby

Flash Flood Warnings in Pennsylvania, 2019 Every flash flood warning in 2019

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.