Alert archive / Pennsylvania / Flash Flood Warnings in 2011

Flash Flood Warning 33, NWS Philadelphia/Mount Holly

August 18, 2011Chester County, Pennsylvania

NWS Philadelphia/Mount Holly issued this flash flood warning at Aug 18, 2011, 6:59 PM EDT for Chester 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 18, 2011, 6:59 PM EDT (22:59 UTC)
Expired: Aug 18, 2011, 9:16 PM EDT
In force: 2 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), 121 km from the middle of the area, began a volume at 23:01 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

Phillips Aaf/Abe, MD (KAPG), launched 12:00Z, 11.0 hours before the alert went out and 41 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: 780 J/kg
Mixed-layer CIN: -64 J/kg
Mixed-layer LCL: 1022 m above ground
0-6 km bulk shear: 16 kt
0-1 km storm-relative helicity: 83 m²/s²
0-3 km storm-relative helicity: 143 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

657 
WGUS51 KPHI 182259
FFWPHI
PAC029-190300-
/O.NEW.KPHI.FF.W.0033.110818T2259Z-110819T0300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
659 PM EDT THU AUG 18 2011

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

* FLASH FLOOD WARNING FOR...
  SOUTHWESTERN CHESTER COUNTY...

* UNTIL 1100 PM EDT...

* AT 654 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
  VERY HEAVY RAIN FROM A THUNDERSTORM OVER SOUTHWESTERN CHESTER
  COUNTY.

* LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO RURAL AREAS
  OF SOUTHWESTERN CHESTER COUNTY.

ADDITIONAL RAINFALL AMOUNTS OF ONE INCH ARE POSSIBLE IN THE WARNED AREA.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

PLEASE REPORT FLOODING...HAIL OR WIND DAMAGE TO THE NATIONAL WEATHER
SERVICE BY CALLING TOLL FREE...1-877-633-6772.

&&

LAT...LON 3975 7610 3978 7607 3985 7603 3987 7601
      3992 7601 3993 7600 3997 7599 3997 7575
      3978 7574 3973 7578 3973 7612 3975 7612

$$

HEAVENER

1 follow-up statement

951 
WGUS71 KPHI 190116
FFSPHI

FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
916 PM EDT THU AUG 18 2011

PAC029-190126-
/O.CAN.KPHI.FF.W.0033.000000T0000Z-110819T0300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
CHESTER PA-
916 PM EDT THU AUG 18 2011

...THE FLASH FLOOD WARNING HAS BEEN CANCELLED FOR SOUTHWESTERN
CHESTER COUNTY...

THE WATERS FROM THE EARLIER HEAVY RAINS ARE RECEDING AND FLOOD WATERS
NO LONGER POSE A THREAT TO LIFE OR PROPERTY. THEREFORE...THE FLASH
FLOOD WARNING HAS BEEN CANCELLED.

LAT...LON 3975 7610 3978 7607 3985 7603 3987 7601
      3992 7601 3993 7600 3997 7599 3997 7575
      3978 7574 3973 7578 3973 7612 3975 7612

$$

IOVINO

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 18, 2:57 AM EDT	Special Weather Statement	PHI	Berks	63 min
Aug 18, 3:53 AM EDT	Special Weather Statement	PHI	Berks	52 min
Aug 18, 4:48 AM EDT	Special Weather Statement	PHI	Chester, Montgomery	57 min
Aug 18, 5:45 AM EDT	Special Weather Statement	PHI	Delaware, Montgomery, Philadelphia	60 min
Aug 18, 6:04 AM EDT	Special Weather Statement	PHI	Berks, Chester	41 min
Aug 18, 6:35 AM EDT	Areal Flood Advisory	PHI	Berks, Bucks, Chester, Delaware, Lehigh, Montgomery and 2 more	3 hr
Aug 18, 7:29 AM EDT	Special Weather Statement	PHI	Bucks, Delaware, Montgomery, Philadelphia	61 min
Aug 18, 8:16 AM EDT	Special Weather Statement	PHI	Philadelphia	59 min
Aug 18, 9:29 AM EDT	Areal Flood Advisory	PHI	Delaware	2 hr
Aug 18, 3:12 PM EDT	Flash Flood Watch	PHI	Berks, Carbon, Delaware, Lehigh, Monroe, Northampton and 1 more	29 hr
Aug 18, 5:30 PM EDT	Special Weather Statement	PHI	Monroe	60 min
Aug 18, 5:48 PM EDT	Severe Thunderstorm Warning	PHI	Chester	57 min
Aug 18, 6:18 PM EDT	Special Weather Statement	PHI	Chester	57 min
Aug 18, 6:39 PM EDT	Severe Thunderstorm Warning	PHI	Chester	66 min
Aug 18, 7:14 PM EDT	Severe Thunderstorm Warning	PHI	Chester, Delaware	50 min
Aug 18, 7:28 PM EDT	Special Weather Statement	PHI	Chester	62 min
Aug 18, 7:31 PM EDT	Special Weather Statement	PHI	Monroe	59 min
Aug 18, 7:37 PM EDT	Severe Thunderstorm Warning	PHI	Delaware, Philadelphia	53 min
Aug 18, 7:47 PM EDT	Areal Flood Advisory	PHI	Carbon, Monroe, Northampton	3 hr
Aug 18, 7:58 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Montgomery	31 min
Aug 18, 7:59 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Delaware, Montgomery, Philadelphia	61 min

Nearby

Flash Flood Warnings in Pennsylvania, 2011 Every flash flood warning in 2011

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.