Alert archive / Pennsylvania / Flash Flood Warnings in 2020
Flash Flood Warning 54, NWS Philadelphia/Mount Holly
NWS Philadelphia/Mount Holly issued this flash flood warning at Aug 12, 2020, 1:47 PM EDT for Chester County, Delaware 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
- Aug 12, 2020, 1:47 PM EDT (17:47 UTC)
- Expired
- Aug 12, 2020, 3:52 PM EDT
- In force
- 2 hr
- Issued by
- NWS Philadelphia/Mount Holly
- Area
- Storm-based polygon
- Flood severity
- None
Counties Chester County, PA, Delaware County, PA
The radar
The Philadelphia radar (KDIX), 91 km from the middle of the area, began a volume at 17:46 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 202 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.
- Mixed-layer CAPE
- 127 J/kg
- Mixed-layer CIN
- -149 J/kg
- Mixed-layer LCL
- 1202 m above ground
- 0-6 km bulk shear
- 15 kt
- 0-1 km storm-relative helicity
- 0 m²/s²
- 0-3 km storm-relative helicity
- 48 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
790
WGUS51 KPHI 121747
FFWPHI
PAC029-045-122045-
/O.NEW.KPHI.FF.W.0054.200812T1747Z-200812T2045Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Mount Holly NJ
147 PM EDT Wed Aug 12 2020
The National Weather Service in Mount Holly NJ has issued a
* Flash Flood Warning for...
East central Chester County in southeastern Pennsylvania...
Central Delaware County in southeastern Pennsylvania...
* Until 445 PM EDT.
* At 146 PM EDT, Doppler radar indicated thunderstorms producing
heavy rain across the warned area. Up to two inches has fallen so
far, with additional rain expected. Flash flooding is expected to
begin shortly.
HAZARD...Flash flooding caused by thunderstorms.
SOURCE...Radar indicated.
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 could experience flooding include...
West Chester, Westtown, Gradyville, Cheyney, Broomall, Paoli,
Newtown Square, Lima, Trout Lake, Concordville, Radnor Township,
Drexel Hill, West Goshen, Media, Malvern, Chester Heights,
Springfield, Upper Providence Township, Devon-Berwyn and Exton.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Protecting yourself from immediate threats to life and safety shall
take priority. Whenever possible, as long as it does not cause
greater harm, all COVID-19 protective action guidance should be
followed.
Turn around...don't drown when encountering flooded roads. Most flood
deaths occur in vehicles.
Excessive runoff from heavy rainfall will cause flooding of small
creeks and streams, urban areas, highways, streets, and underpasses
as well as other drainage areas and low lying spots.
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 4008 7542 3996 7527 3985 7563 4003 7563
FLASH FLOOD...RADAR INDICATED
EXPECTED RAINFALL...1-2 INCHES IN 1 HOUR
$$
JJM1 follow-up statement
506 WGUS71 KPHI 121952 FFSPHI Flash Flood Statement National Weather Service Mount Holly NJ 352 PM EDT Wed Aug 12 2020 PAC029-045-121959- /O.CAN.KPHI.FF.W.0054.000000T0000Z-200812T2045Z/ /00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/ Chester PA-Delaware PA- 352 PM EDT Wed Aug 12 2020 ...THE FLASH FLOOD WARNING FOR EAST CENTRAL CHESTER AND CENTRAL DELAWARE COUNTIES IS CANCELLED... While some flooding continues...the area is covered by a subsequent flash flood warning which is valid through 645 PM. This flash flood warning is therefore cancelled. LAT...LON 4008 7542 3996 7527 3985 7563 4003 7563 $$ JJM
The office that day
Everything else NWS Philadelphia/Mount Holly issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 12, 11:48 AM EDT | Special Weather Statement | PHI | Philadelphia | 27 min |
| Aug 12, 12:43 PM EDT | Areal Flood Advisory | PHI | Bucks, Chester, Delaware, Montgomery, Philadelphia | 3 hr |
| Aug 12, 1:12 PM EDT | Severe Thunderstorm Warning | PHI | Chester, Delaware, Montgomery, Philadelphia | 48 min |
| Aug 12, 1:54 PM EDT | Severe Thunderstorm Warning | PHI | Chester, Delaware, Montgomery, Philadelphia | 51 min |
| Aug 12, 2:04 PM EDT | Severe Thunderstorm Warning | PHI | Bucks, Montgomery, Philadelphia | 21 min |
| Aug 12, 2:40 PM EDT | Flash Flood Warning | PHI | Chester, Delaware, Montgomery, Philadelphia | 3 hr |
| Aug 12, 2:44 PM EDT | Severe Thunderstorm Warning | PHI | Delaware, Philadelphia | 46 min |
| Aug 12, 3:20 PM EDT | Severe Thunderstorm Warning | PHI | Chester, Delaware | 29 min |
| Aug 12, 3:36 PM EDT | Flash Flood Warning | PHI | Chester | 108 min |
| Aug 12, 5:04 PM EDT | Areal Flood Advisory | PHI | Lehigh, Northampton | 56 min |
| Aug 12, 5:09 PM EDT | Areal Flood Warning | PHI | Berks | 51 min |
Nearby
Flash Flood Warnings in Pennsylvania, 2020Every 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.