Alert archive / Pennsylvania / Areal Flood Warnings in 2021
Areal Flood Warning 15, NWS Philadelphia/Mount Holly
NWS Philadelphia/Mount Holly issued this areal flood warning at Aug 19, 2021, 4:33 AM EDT for Chester County, Delaware County, Pennsylvania. It was in force for 4 hr. 1 report 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 19, 2021, 4:33 AM EDT (08:33 UTC)
- Expired
- Aug 19, 2021, 8:30 AM EDT
- In force
- 4 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), 89 km from the middle of the area, began a volume at 08:37 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
| Time | Report | Where | Remark |
|---|---|---|---|
| Aug 19, 6:10 AM EDT | HEAVY RAIN 3.71 | Wayne, PA | 3.30 INCHES FELL IN ONE HOUR. |
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, 8.6 hours before the alert went out and 208 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
- 1288 J/kg
- Mixed-layer CIN
- -8 J/kg
- Mixed-layer LCL
- 1100 m above ground
- 0-6 km bulk shear
- 30 kt
- 0-1 km storm-relative helicity
- 126 m²/s²
- 0-3 km storm-relative helicity
- 171 m²/s²
- Significant tornado parameter
- 0.6
- Supercell composite
- 5.9
The text
As transmitted.
751
WGUS41 KPHI 190833
FLWPHI
BULLETIN - IMMEDIATE BROADCAST REQUESTED
Flood Warning
National Weather Service Mount Holly NJ
433 AM EDT Thu Aug 19 2021
PAC029-045-191230-
/O.NEW.KPHI.FA.W.0015.210819T0833Z-210819T1230Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Chester PA-Delaware PA-
433 AM EDT Thu Aug 19 2021
The National Weather Service in Mount Holly has issued a
* Flood Warning for...
East Central Chester County in southeastern Pennsylvania...
North Central Delaware County in southeastern Pennsylvania...
* Until 830 AM EDT.
* At 433 AM EDT, Doppler radar and automated rain gauges indicated
heavy rain due to thunderstorms. Rain has ended across the area,
but residual flooding is still ongoing. Some road closures remain
in place and some creeks and small streams remain out of their
banks. Areas of flooding will continue for another few hours as
flood waters slowly recede.
* Some locations that will experience flooding include...
Paoli, Newtown Square, Gradyville, Valley Forge, Radnor Township,
King Of Prussia, West Goshen, Malvern, Devon-Berwyn, Chesterbrook,
and Upper Providence Township.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Turn around...don't drown when encountering flooded roads. Most
flood deaths occur in vehicles.
&&
LAT...LON 3997 7557 4011 7548 4011 7547 4010 7546
4009 7546 4009 7544 4009 7543 4009 7541
4006 7539 4007 7536 4004 7534 3993 7542
$$
JEO1 follow-up statement
805
WGUS81 KPHI 191228
FLSPHI
Flood Statement
National Weather Service Mount Holly NJ
828 AM EDT Thu Aug 19 2021
PAC029-045-191238-
/O.EXP.KPHI.FA.W.0015.000000T0000Z-210819T1230Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Chester PA-Delaware PA-
828 AM EDT Thu Aug 19 2021
...FLOOD WARNING WILL EXPIRE AT 830 AM EDT THIS MORNING FOR EAST
CENTRAL CHESTER AND NORTH CENTRAL DELAWARE COUNTIES...
Flood waters have receded. The heavy rain has ended. Flooding is no
longer expected to pose a threat. Please continue to heed remaining
road closures.
LAT...LON 3997 7557 4011 7548 4011 7547 4010 7546
4009 7546 4009 7544 4009 7543 4009 7541
4006 7539 4007 7536 4004 7534 3993 7542
$$
BAHThe office that day
Everything else NWS Philadelphia/Mount Holly issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 18, 8:53 PM EDT | Areal Flood Advisory | PHI | Berks | 3 hr |
| Aug 18, 9:10 PM EDT | Areal Flood Advisory | PHI | Lehigh, Monroe, Northampton | 3 hr |
| Aug 18, 9:30 PM EDT | Flash Flood Warning | PHI | Berks | 2 hr |
| Aug 18, 9:35 PM EDT | Areal Flood Advisory | PHI | Berks, Lehigh | 3 hr |
| Aug 18, 9:45 PM EDT | Areal Flood Advisory | PHI | Berks | 3 hr |
| Aug 18, 9:47 PM EDT | Special Weather Statement | PHI | Berks | 58 min |
| Aug 18, 10:16 PM EDT | Flash Flood Warning | PHI | Berks, Lehigh | 3 hr |
| Aug 18, 10:44 PM EDT | Flash Flood Warning | PHI | Lehigh, Monroe, Northampton | 4 hr |
| Aug 18, 10:50 PM EDT | Flash Flood Warning | PHI | Bucks, Chester, Montgomery | 4 hr |
| Aug 18, 11:19 PM EDT | Areal Flood Advisory | PHI | Bucks, Lehigh, Northampton | 3 hr |
| Aug 18, 11:19 PM EDT | Special Weather Statement | PHI | Bucks, Chester, Montgomery | 41 min |
| Aug 18, 11:47 PM EDT | Flash Flood Warning | PHI | Chester | 2 hr |
| Aug 19, 12:04 AM EDT | Special Weather Statement | PHI | Bucks, Delaware, Montgomery | 71 min |
| Aug 19, 12:26 AM EDT | Tornado Warning | PHI | Bucks, Montgomery | 34 min |
| Aug 19, 12:31 AM EDT | Flash Flood Warning | PHI | Bucks, Chester, Delaware, Montgomery | 4 hr |
| Aug 19, 12:44 AM EDT | River Flood Warning | PHI | Chester | 5 hr |
| Aug 19, 12:47 AM EDT | Tornado Warning | PHI | Chester, Delaware, Montgomery, Philadelphia | 28 min |
| Aug 19, 12:48 AM EDT | Tornado Warning | PHI | Bucks | 27 min |
| Aug 19, 1:14 AM EDT | Special Weather Statement | PHI | Bucks, Delaware, Philadelphia | 91 min |
| Aug 19, 1:30 AM EDT | Flash Flood Warning | PHI | Bucks, Delaware, Montgomery, Philadelphia | 4 hr |
| Aug 19, 2:05 AM EDT | Areal Flood Advisory | PHI | Bucks | 3 hr |
| Aug 19, 2:13 AM EDT | Flash Flood Warning | PHI | Bucks, Philadelphia | 4 hr |
| Aug 19, 6:09 AM EDT | Areal Flood Warning | PHI | Bucks, Philadelphia | 3 hr |
| Aug 19, 8:50 AM EDT | Areal Flood Warning | PHI | Montgomery, Philadelphia | 3 hr |
| Aug 19, 10:40 AM EDT | Areal Flood Warning | PHI | Delaware | 3 hr |
Nearby
Areal Flood Warnings in Pennsylvania, 2021Every areal flood warning in 2021
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.