Alert archive / Pennsylvania / Flash Flood Warnings in 2009

Flash Flood Warning 11, NWS Philadelphia/Mount Holly

June 13, 2009Chester County, Pennsylvania

NWS Philadelphia/Mount Holly issued this flash flood warning at Jun 13, 2009, 6:06 PM EDT for Chester County, Pennsylvania. It was in force for 2 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: Jun 13, 2009, 6:06 PM EDT (22:06 UTC)
Expired: Jun 13, 2009, 8:30 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 Philadelphia radar (KDIX), 108 km from the middle of the area, began a volume at 22:06 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
Jun 13, 6:50 PM EDT	FLASH FLOOD	Exton, PA	SEVERAL ROADS FLOODED

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 12:00Z, 10.1 hours before the alert went out and 192 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: 18 J/kg
Mixed-layer CIN: -76 J/kg
Mixed-layer LCL: 989 m above ground
0-6 km bulk shear: 30 kt
0-1 km storm-relative helicity: -30 m²/s²
0-3 km storm-relative helicity: 38 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.

000 
WGUS51 KPHI 132206
FFWPHI
PAC029-140030-
/O.NEW.KPHI.FF.W.0011.090613T2206Z-090614T0030Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
606 PM EDT SAT JUN 13 2009

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

* FLASH FLOOD WARNING FOR...
  CHESTER COUNTY IN SOUTHEAST PENNSYLVANIA...
  THIS INCLUDES THE CITY OF WEST CHESTER...

* UNTIL 830 PM EDT

* AT 604 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED   
  VERY HEAVY RAINS ESPECIALLY ACROSS THE NORTHERN HALF OF THE       
  COUNTY. RAINFALL AMOUNTS COULD EXCEED 4 INCHES IN SOME AREAS.

* LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO PUGHTOWN...
  GLENMOORE...CHESTER SPRINGS...CEDARVILLE...PAOLI...LIONVILLE AND
  ELVERSON

PRECAUTIONARY/PREPAREDNESS ACTIONS...

DO NOT DRIVE YOUR VEHICLE INTO AREAS WHERE THE WATER COVERS THE
ROADWAY. THE WATER DEPTH MAY BE TOO GREAT TO ALLOW YOUR CAR TO CROSS
SAFELY. MOVE TO HIGHER GROUND.

&&

LAT...LON 4014 7587 4025 7567 4019 7559 4010 7548
      4007 7543 3999 7547 3992 7557 3984 7574
      3984 7600

$$

EBERWINE

The office that day

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

Issued	Product	Office	Counties	Lasted
Jun 13, 2:27 PM EDT	Areal Flood Advisory	PHI	Chester	4 hr
Jun 13, 2:32 PM EDT	Flash Flood Warning	PHI	Bucks	2 hr
Jun 13, 2:33 PM EDT	Flash Flood Warning	PHI	Carbon, Lehigh, Monroe, Northampton	112 min
Jun 13, 2:57 PM EDT	Flash Flood Warning	PHI	Montgomery	2 hr
Jun 13, 3:17 PM EDT	Areal Flood Advisory	PHI	Bucks	3 hr
Jun 13, 4:07 PM EDT	Flash Flood Warning	PHI	Bucks, Montgomery, Philadelphia	6 hr
Jun 13, 4:59 PM EDT	Areal Flood Advisory	PHI	Chester	4 hr
Jun 13, 5:16 PM EDT	River Flood Warning	PHI	Bucks	13 hr
Jun 13, 6:39 PM EDT	Severe Thunderstorm Warning	PHI	Monroe	66 min
Jun 13, 7:29 PM EDT	Severe Thunderstorm Warning	PHI	Carbon, Monroe	61 min

Nearby

Flash Flood Warnings in Pennsylvania, 2009 Every flash flood warning in 2009

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.