Alert archive / Pennsylvania / Flash Flood Warnings in 2019

Flash Flood Warning 81, NWS Philadelphia/Mount Holly

August 14, 20194 counties in Pennsylvania

NWS Philadelphia/Mount Holly issued this flash flood warning at Aug 14, 2019, 9:12 PM EDT for 4 counties in Pennsylvania. It was in force for 3 hr. 10 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
Aug 14, 2019, 9:12 PM EDT (01:12 UTC)
Expired
Aug 15, 2019, 12:15 AM EDT
In force
3 hr
Issued by
NWS Philadelphia/Mount Holly
Area
Storm-based polygon
Flood severity
None

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

The radar

The Philadelphia radar (KDIX), 81 km from the middle of the area, began a volume at 01:15 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

TimeReportWhereRemark
Aug 14, 9:17 PM EDTFLASH FLOOD1 Se East Whiteland Twp, PALANCASTER AVENUE FLOODED AND CLOSED. NEARLY TWO FEET OF WATER ON PORTIONS OF THE ROAD WITH VEHICLES STUCK.
Aug 14, 9:18 PM EDTFLASH FLOOD1 Ne Wayne, PAWATER RESCUE IN PROGRESS NEAR THE INTERSECTION OF MATSONFORD ROAD AND KING OF PRUSSIA ROAD.
Aug 14, 9:19 PM EDTHEAVY RAIN 1.5Wayne, PA1.5 INCHES IN 45 MINUTES.
Aug 14, 9:21 PM EDTFLASH FLOOD2 N Villanova, PAWATER RESCUE IN PROGRESS AT MATSONFORD ROAD AND GRISCOM ROAD.
Aug 14, 9:23 PM EDTFLOODBroomall, PAMPING REPORT OF STREET FLOODING IN THIS AREA.
Aug 14, 9:33 PM EDTFLASH FLOODBerwyn, PAU.S. HIGHWAY 30 CLOSED NEAR LAKESIDE AVENUE FROM FLASH FLOODING.
Aug 14, 9:41 PM EDTFLASH FLOOD1 Nne Berwyn, PADOWNED TREE FROM HEAVY RAIN AND FLASH FLOODING NEAR THE VALLEY FORGE ROAD AND DEVON STATE ROAD INTERSECTION.
Aug 14, 9:42 PM EDTFLOOD1 Wnw Villanova, PAFLOODING ON INTERSTATE 476 NEAR THE U.S. HIGHWAY 30 INTERCHANGE. LANE RESTRICTIONS IN PLACE.
Aug 14, 9:43 PM EDTFLASH FLOOD1 Nw Conshohocken, PACONSHOHOCKEN ROAD, FAIRFIELD ROAD, AND NEW ELM STREET CLOSED FROM FLASH FLOODING.
Aug 14, 10:04 PM EDTFLASH FLOOD1 Nne Lawrence Park, PAWATER RESCUE IN PROGRESS NEAR THE INTERCHANGE OF INTERSTATE 476 AND WEST CHESTER PIKE.

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 00:00Z, 1.2 hours before the alert went out and 217 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-pSkew-T log-p diagram, Washington/Dulle, VA at 00:00Z on 2019-08-15Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 378 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Washington/Dulle, VA at 00:00Z on 2019-08-15The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 9 square meters per square second.19395878Sfc1 km3 km6 km9 kmRMLM
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
378 J/kg
Mixed-layer CIN
-39 J/kg
Mixed-layer LCL
1458 m above ground
0-6 km bulk shear
35 kt
0-1 km storm-relative helicity
9 m²/s²
0-3 km storm-relative helicity
35 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.1

Open this sounding in Storm Lab

The text

As transmitted.

347 
WGUS51 KPHI 150112
FFWPHI
PAC029-045-091-101-150415-
/O.NEW.KPHI.FF.W.0081.190815T0112Z-190815T0415Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Mount Holly NJ
912 PM EDT Wed Aug 14 2019

The National Weather Service in Mount Holly NJ has issued a

* Flash Flood Warning for...
  Southern Montgomery County in southeastern Pennsylvania...
  Northeastern Chester County in southeastern Pennsylvania...
  Northwestern Philadelphia County in southeastern Pennsylvania...
  Northeastern Delaware County in southeastern Pennsylvania...

* Until 1215 AM EDT.

* At 912 PM EDT, Doppler radar indicated thunderstorms producing
  heavy rain across the warned area. Up to two inches of rain have 
  already fallen in as little as 30 minutes. Flash flooding is 
  expected to begin shortly in the areas of heaviest rain.

* Some locations that could experience flooding include...
  Philadelphia, West Chester, Norristown, Phoenixville, West
  Norriton, East Norriton, Coatesville, Westtown, Downingtown,
  Conshohocken, Ambler, Collegeville, Royersford, Jenkintown,
  Narberth, Trappe, Rockledge, Abington, Bryn Athyn and Pughtown.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4021 7520 4013 7504 4002 7515 3998 7526
      3989 7580 4017 7580

$$

CS
3 follow-up statements
771 
WGUS71 KPHI 150143
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
943 PM EDT Wed Aug 14 2019

PAC029-045-091-101-150415-
/O.CON.KPHI.FF.W.0081.000000T0000Z-190815T0415Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Montgomery PA-Chester PA-Philadelphia PA-Delaware PA-
943 PM EDT Wed Aug 14 2019

...THE FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 1215 AM EDT FOR
SOUTHERN MONTGOMERY...NORTHEASTERN CHESTER...NORTHWESTERN
PHILADELPHIA AND NORTHEASTERN DELAWARE COUNTIES...

At 942 PM EDT, local law enforcement reported flash flooding in 
Wayne, Malvern, and Radnor. Several water rescues are occurring at 
this time in these areas, with several roads inundated. Flash 
flooding is expected to continue for the next couple of hours.

Some locations that could experience flooding include...
Philadelphia, West Chester, Norristown, Phoenixville, West Norriton,
East Norriton, Coatesville, Westtown, Downingtown, Conshohocken,
Ambler, Collegeville, Royersford, Jenkintown, Narberth, Trappe,
Rockledge, Abington, Bryn Athyn and Pughtown.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4021 7520 4013 7504 4002 7515 3998 7526
      3989 7580 4017 7580

$$

CS
889 
WGUS71 KPHI 150219
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
1019 PM EDT Wed Aug 14 2019

PAC029-045-091-101-150415-
/O.CON.KPHI.FF.W.0081.000000T0000Z-190815T0415Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Montgomery PA-Chester PA-Philadelphia PA-Delaware PA-
1019 PM EDT Wed Aug 14 2019

...THE FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 1215 AM EDT FOR
SOUTHERN MONTGOMERY...NORTHEASTERN CHESTER...NORTHWESTERN
PHILADELPHIA AND NORTHEASTERN DELAWARE COUNTIES...

At 1017 PM EDT, local law enforcement reported flash flooding in 
Wayne, Radnor, Conshohocken, Malvern, and Marple Township. Several 
water rescues have been reported in these areas, and numerous roads 
are inundated and closed at this time. Though the heavy rainfall has 
ended, runoff will continue to cause flash flooding for the next 
couple of hours.

Some locations that could experience flooding include...
Philadelphia, West Chester, Norristown, Phoenixville, West Norriton,
East Norriton, Westtown, Downingtown, Conshohocken, Ambler,
Collegeville, Royersford, Jenkintown, Narberth, Trappe, Rockledge,
Abington, Bryn Athyn, Bryn Mawr and Marshallton.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4021 7520 4013 7504 4002 7515 3998 7526
      3989 7580 4018 7564

$$

CS
768 
WGUS71 KPHI 150407
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
1207 AM EDT Thu Aug 15 2019

PAC029-045-091-101-150416-
/O.EXP.KPHI.FF.W.0081.000000T0000Z-190815T0415Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Montgomery PA-Chester PA-Philadelphia PA-Delaware PA-
1207 AM EDT Thu Aug 15 2019

...THE FLASH FLOOD WARNING FOR SOUTHERN MONTGOMERY...NORTHEASTERN
CHESTER...NORTHWESTERN PHILADELPHIA AND NORTHEASTERN DELAWARE
COUNTIES WILL EXPIRE AT 1215 AM EDT...

Most waterways in the warned area have already crested or are in the 
process of cresting. Flood waters will continue to recede. Please 
continue to heed any remaining road closures.

LAT...LON 4021 7520 4013 7504 4002 7515 3998 7526
      3989 7580 4018 7564

$$

SFJ

The office that day

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

IssuedProductOfficeCountiesLasted
Aug 14, 8:09 PM EDTSpecial Weather StatementPHIChester36 min
Aug 14, 8:16 PM EDTAreal Flood AdvisoryPHIBucks, Chester, Montgomery, Philadelphia119 min
Aug 14, 8:48 PM EDTSpecial Weather StatementPHIDelaware, Philadelphia42 min
Aug 14, 8:56 PM EDTAreal Flood AdvisoryPHIChester, Delaware, Montgomery, Philadelphia2 hr
Aug 15, 2:23 AM EDTDense Fog AdvisoryPHIBucks, Chester, Delaware, Montgomery, Philadelphia6 hr
Aug 15, 3:42 PM EDTSevere Thunderstorm WarningPHICarbon48 min
Aug 15, 4:22 PM EDTSevere Thunderstorm WarningPHICarbon, Monroe, Northampton53 min
Aug 15, 5:18 PM EDTSpecial Weather StatementPHIMonroe27 min

Nearby

Flash Flood Warnings in Pennsylvania, 2019Every 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.