Alert archive / Pennsylvania / Flash Flood Warnings in 2020

Flash Flood Warning 2, NWS Philadelphia/Mount Holly

April 13, 2020Chester County, Pennsylvania

NWS Philadelphia/Mount Holly issued this flash flood warning at Apr 13, 2020, 1:47 PM EDT for Chester County, Pennsylvania. It was in force for 3 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: Apr 13, 2020, 1:47 PM EDT (17:47 UTC)
Expired: Apr 13, 2020, 4:47 PM EDT
In force: 3 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), 124 km from the middle of the area, began a volume at 17:48 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, 5.8 hours before the alert went out and 158 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 712 m above ground
0-6 km bulk shear: 75 kt
0-1 km storm-relative helicity: 487 m²/s²
0-3 km storm-relative helicity: 684 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

539 
WGUS51 KPHI 131747
FFWPHI
PAC029-132145-
/O.NEW.KPHI.FF.W.0002.200413T1747Z-200413T2145Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Mount Holly NJ
147 PM EDT Mon Apr 13 2020

The National Weather Service in Mount Holly NJ has issued a

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

* Until 545 PM EDT.

* At 146 PM EDT, Doppler radar indicated heavy rain across portions 
  of the warned area. Up to three inches of rain have already 
  fallen. Flash flooding is expected in the areas of heaviest rain. 
  Thunderstorms in York county are also moving toward Chester county 
  and could provide the area with additional heavy rain in the next 
  hour.

* Some locations that could experience flooding include...
  Coatesville, Downingtown, Oxford, Parkesburg, Homeville, Glen Roy,
  Cochranville, Glenmoore, Chester Springs, Pughtown, Lionville,
  Mount Vernon, Marshallton, Lionville-Marchwood, Atglen, South
  Coatesville, Modena, Exton and Thorndale.

This includes Pennsylvania Turnpike near exit 312.
 
PRECAUTIONARY/PREPAREDNESS ACTIONS...

In hilly terrain there are hundreds of low water crossings which are
potentially dangerous in heavy rain. Do not attempt to cross flooded
roads. Find an alternate route.

&&

LAT...LON 3973 7610 3974 7609 3976 7606 3981 7603
      3983 7604 3987 7599 3994 7598 3995 7600
      4000 7596 4023 7571 4004 7552 3972 7605
      3972 7613

$$

Kruzdlo

1 follow-up statement

552 
WGUS71 KPHI 132047
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
447 PM EDT Mon Apr 13 2020

PAC029-132053-
/O.CAN.KPHI.FF.W.0002.000000T0000Z-200413T2145Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Chester PA-
447 PM EDT Mon Apr 13 2020

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

The heavy rain has ended. Runoff has made it to area creeks and 
streams. Water remains high including along the East Branch 
Brandywine and French Creek. Please continue to heed any remaining 
road closures.

LAT...LON 3973 7610 3974 7609 3976 7606 3981 7603
      3983 7604 3987 7599 3994 7598 3995 7600
      4000 7596 4023 7571 4004 7552 3972 7605
      3972 7613

$$

Kruzdlo

The office that day

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

Issued	Product	Office	Counties	Lasted
Apr 13, 6:11 AM EDT	Areal Flood Advisory	PHI	Berks, Chester, Delaware, Montgomery	4 hr
Apr 13, 6:48 AM EDT	Areal Flood Advisory	PHI	Delaware, Montgomery, Philadelphia	4 hr
Apr 13, 8:03 AM EDT	Areal Flood Advisory	PHI	Bucks	4 hr
Apr 13, 10:58 AM EDT	River Flood Warning	PHI	Chester	6 hr
Apr 13, 11:09 AM EDT	Areal Flood Warning	PHI	Chester, Delaware	3 hr
Apr 13, 12:29 PM EDT	River Flood Warning	PHI	Chester, Delaware	12 hr
Apr 13, 1:01 PM EDT	Areal Flood Advisory	PHI	Berks, Carbon, Lehigh, Monroe, Northampton	4 hr
Apr 13, 1:07 PM EDT	Flash Flood Warning	PHI	Berks, Carbon, Lehigh, Northampton	4 hr
Apr 13, 1:27 PM EDT	Severe Thunderstorm Warning	PHI	Chester	33 min
Apr 13, 2:23 PM EDT	Areal Flood Warning	PHI	Montgomery, Philadelphia	4 hr
Apr 13, 2:37 PM EDT	Areal Flood Advisory	PHI	Berks, Bucks, Chester, Delaware, Lehigh, Montgomery and 2 more	2 hr
Apr 13, 2:41 PM EDT	Severe Thunderstorm Warning	PHI	Chester, Delaware	64 min
Apr 13, 4:35 PM EDT	Areal Flood Warning	PHI	Montgomery	2 hr

Nearby

Flash Flood Warnings in Pennsylvania, 2020 Every flash flood warning in 2020

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.