Alert archive / Pennsylvania / Flash Flood Warnings in 2019

Flash Flood Warning 57, NWS Philadelphia/Mount Holly

July 18, 2019Chester County, Pennsylvania; New Castle County, Delaware

NWS Philadelphia/Mount Holly issued this flash flood warning at Jul 18, 2019, 2:55 PM EDT for Chester County, Pennsylvania; New Castle County, Delaware. It was in force for 4 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 18, 2019, 2:55 PM EDT (18:55 UTC)
Expired: Jul 18, 2019, 7:00 PM EDT
In force: 4 hr
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Flood severity: None

Counties New Castle County, DE, Chester County, PA

The radar

The Dover AFB radar (KDOX), 115 km from the middle of the area, began a volume at 18:58 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, 6.9 hours before the alert went out and 157 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: 208 J/kg
Mixed-layer CIN: -96 J/kg
Mixed-layer LCL: 1102 m above ground
0-6 km bulk shear: 11 kt
0-1 km storm-relative helicity: 41 m²/s²
0-3 km storm-relative helicity: 66 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

592 
WGUS51 KPHI 181855
FFWPHI
DEC003-PAC029-182300-
/O.NEW.KPHI.FF.W.0057.190718T1855Z-190718T2300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Mount Holly NJ
255 PM EDT Thu Jul 18 2019

The National Weather Service in Mount Holly NJ has issued a

* Flash Flood Warning for...
  Northwestern New Castle County in northern Delaware...
  Southwestern Chester County in southeastern Pennsylvania...

* Until 700 PM EDT.

* At 254 PM EDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Up to two inches of rain have 
  already fallen in a short amount of time. Flash flooding is 
  expected to begin shortly in the areas of heaviest rain.


* Some locations that could experience flooding include...
  Kennett Square, Oxford, West Grove, Glen Roy, North Star, Mount
  Vernon, Ladenberg, Kemblesville, Hockessin, Ashland, Greenville,
  Pike Creek, Avondale and Toughkenamon.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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 3974 7612 3973 7610 3976 7606 3983 7602
      3985 7602 3990 7560 3986 7560 3979 7557
      3972 7587 3972 7613

$$

Robertson

2 follow-up statements

943 
WGUS71 KPHI 182045
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
445 PM EDT Thu Jul 18 2019

DEC003-PAC029-182300-
/O.CON.KPHI.FF.W.0057.000000T0000Z-190718T2300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
New Castle DE-Chester PA-
445 PM EDT Thu Jul 18 2019

...THE FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 700 PM EDT FOR
NORTHWESTERN NEW CASTLE AND SOUTHWESTERN CHESTER COUNTIES...

At 444 PM EDT, Doppler radar indicated two to three inches of rain 
from earlier thunderstorms. Flash flooding has occurred with road 
closures and water rescues.

Some locations that could experience flooding include...
Kennett Square, Oxford, West Grove, Glen Roy, North Star, Mount
Vernon, Ladenberg, Kemblesville, Hockessin, Ashland, Greenville, Pike
Creek, Avondale and Toughkenamon.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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 3974 7612 3973 7610 3976 7606 3983 7602
      3985 7602 3990 7560 3986 7560 3979 7557
      3972 7587 3972 7613

$$

Robertson

733 
WGUS71 KPHI 182254
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
654 PM EDT Thu Jul 18 2019

DEC003-PAC029-182300-
/O.EXP.KPHI.FF.W.0057.000000T0000Z-190718T2300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
New Castle DE-Chester PA-
654 PM EDT Thu Jul 18 2019

...THE FLASH FLOOD WARNING FOR NORTHWESTERN NEW CASTLE AND
SOUTHWESTERN CHESTER COUNTIES WILL EXPIRE AT 700 PM EDT...

The heavy rain has ended. Flash flooding is no longer expected to 
pose a threat. Please continue to heed any remaining road closures 
as the water may be slow to recede in some areas.

LAT...LON 3974 7612 3973 7610 3976 7606 3983 7602
      3985 7602 3990 7560 3986 7560 3979 7557
      3972 7587 3972 7613

$$

Robertson

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 17, 8:01 PM EDT	Areal Flood Advisory	PHI	Northampton	88 min
Jul 17, 8:15 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Delaware, Montgomery, Philadelphia	45 min
Jul 18, 1:30 PM EDT	Areal Flood Advisory	PHI	Chester, Delaware, Montgomery, Philadelphia	4 hr
Jul 18, 2:13 PM EDT	Areal Flood Advisory	PHI	Bucks, Montgomery, Philadelphia	4 hr
Jul 18, 2:24 PM EDT	Areal Flood Advisory	PHI	Berks, Bucks, Chester, Lehigh, Montgomery	3 hr
Jul 18, 3:33 PM EDT	Flash Flood Warning	PHI	Chester, Delaware	4 hr
Jul 18, 7:44 PM EDT	Special Weather Statement	PHI	Berks	46 min
Jul 17, 8:30 PM EDT	Severe Thunderstorm Warning	PHI	Sussex	45 min
Jul 17, 8:54 PM EDT	Severe Thunderstorm Warning	PHI	Sussex	36 min
Jul 17, 9:09 PM EDT	Areal Flood Advisory	PHI	Sussex	2 hr
Jul 17, 11:34 PM EDT	Areal Flood Advisory	PHI	Sussex	2 hr

Nearby

Flash Flood Warnings in Pennsylvania, 2019 Flash Flood Warnings in Delaware, 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.