Alert archive / Pennsylvania / Flash Flood Warnings in 2012

Flash Flood Warning 1, NWS Philadelphia/Mount Holly

May 16, 2012Chester County, Delaware County, Montgomery County, Pennsylvania

NWS Philadelphia/Mount Holly issued this flash flood warning at May 16, 2012, 12:34 AM EDT for Chester County, Delaware County, Montgomery County, Pennsylvania. It was in force for 4 hr. 2 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: May 16, 2012, 12:34 AM EDT (04:34 UTC)
Expired: May 16, 2012, 4:30 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, Montgomery County, PA

The radar

The Philadelphia radar (KDIX), 78 km from the middle of the area, began a volume at 04:37 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
May 16, 12:41 AM EDT	FLASH FLOOD	Upper Merion Twp, PA	FLASH FLOODING ALONG S. GULF ROAD AS THE GULF CREEK OVERFLOWED ITS BANKS.
May 16, 1:15 AM EDT	FLASH FLOOD	Tredyffrin Twp, PA	EIGHT WATER RESCUES PERFORMED IN TREDYFFRIN AND EASTTOWN TWPS AS THE VALLEY AND DARBY CREEKS OVERFLOWED THEIR BANKS.

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, 4.6 hours before the alert went out and 222 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: 401 J/kg
Mixed-layer CIN: -9 J/kg
Mixed-layer LCL: 1311 m above ground
0-6 km bulk shear: 22 kt
0-1 km storm-relative helicity: 5 m²/s²
0-3 km storm-relative helicity: 58 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.1

Open this sounding in Storm Lab

The text

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

399 
WGUS51 KPHI 160434
FFWPHI
PAC029-045-091-160830-
/O.NEW.KPHI.FF.W.0001.120516T0434Z-120516T0830Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1234 AM EDT WED MAY 16 2012

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

* FLASH FLOOD WARNING FOR...
  SOUTH CENTRAL MONTGOMERY COUNTY...
  NORTH CENTRAL DELAWARE COUNTY...
  EAST CENTRAL CHESTER COUNTY...

* UNTIL 430 AM EDT...

* AT 1228 AM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
  VERY HEAVY RAIN FROM A THUNDERSTORM OVER EAST CENTRAL CHESTER...  
  NORTH CENTRAL DELAWARE AND SOUTH CENTRAL MONTGOMERY COUNTIES. RADAR
  ESTIMATES THAT AS MUCH AS 2.5 INCHES OF RAIN HAS FALLEN IN THIS AREA
  IN THE PAST HOUR...AND WITH MORE HEAVY ON THE WAY.
 
* LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO RURAL AREAS
  OF EAST CENTRAL CHESTER...NORTH CENTRAL DELAWARE AND SOUTH CENTRAL
  MONTGOMERY COUNTIES.

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 4023 7527 4012 7516 4009 7521 4009 7522
      4008 7523 3994 7549 4010 7555

$$

HAYES

2 follow-up statements

391 
WGUS71 KPHI 160526
FFSPHI

FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
126 AM EDT WED MAY 16 2012

PAC029-045-091-160830-
/O.CON.KPHI.FF.W.0001.000000T0000Z-120516T0830Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
MONTGOMERY PA-DELAWARE PA-CHESTER PA-
126 AM EDT WED MAY 16 2012

...A FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 430 AM EDT FOR EAST
CENTRAL CHESTER...NORTH CENTRAL DELAWARE AND SOUTH CENTRAL MONTGOMERY
COUNTIES...

AT 120 AM EDT...DOPPLER RADAR INDICATED THAT THE THUNDERSTORMS 
PRODUCING THE HEAVY RAIN WERE ABOUT TO MOVE EAST OF THE AREA. 
HOWEVER...RUNOFF FROM THE VERY HEAVY RAIN WILL CONTINUE TO POSE A 
FLASH FLOOD THREAT FOR THE NEXT HOUR OR TWO. BE ON THE ALERT FOR 
RAPIDLY RISING WATER ON CREEKS AND STREAMS...AS WELL AS SIGNIFICANT 
URBAN FLOODING.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

PLEASE REPORT FLOODING...HAIL OR WIND DAMAGE BY CALLING YOUR LOCAL
LAW ENFORCEMENT OFFICIALS OR BY CALLING THE NATIONAL WEATHER SERVICE
TOLL FREE AT...1-877-633-6772.

&&

LAT...LON 4023 7527 4012 7516 4009 7521 4009 7522
      4008 7523 3994 7549 4010 7555

$$

HAYES

105 
WGUS71 KPHI 160823
FFSPHI

FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
423 AM EDT WED MAY 16 2012

PAC029-045-091-160833-
/O.EXP.KPHI.FF.W.0001.000000T0000Z-120516T0830Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
MONTGOMERY PA-DELAWARE PA-CHESTER PA-
423 AM EDT WED MAY 16 2012

...THE FLASH FLOOD WARNING WILL EXPIRE AT 430 AM EDT FOR EAST CENTRAL
CHESTER...NORTH CENTRAL DELAWARE AND SOUTH CENTRAL MONTGOMERY
COUNTIES...

THE WATERS FROM THE EARLIER HEAVY RAINS ARE RECEDING AND NO LONGER
POSE A THREAT TO LIFE OR PROPERTY. THEREFORE...THE FLASH FLOOD 
WARNING WILL BE ALLOWED TO EXPIRE.

LAT...LON 4023 7527 4012 7516 4009 7521 4009 7522
      4008 7523 3994 7549 4010 7555

$$

HAYES

The office that day

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

Issued	Product	Office	Counties	Lasted
May 15, 8:19 PM EDT	Special Weather Statement	PHI	Bucks	86 min
May 15, 8:46 PM EDT	Areal Flood Warning	PHI	Northampton	76 min
May 15, 9:00 PM EDT	Special Weather Statement	PHI	Berks	90 min
May 15, 9:49 PM EDT	Special Weather Statement	PHI	Berks, Bucks, Chester, Lehigh, Montgomery	86 min
May 15, 10:45 PM EDT	Areal Flood Advisory	PHI	Chester	57 min
May 15, 11:05 PM EDT	Special Weather Statement	PHI	Bucks, Chester, Delaware, Montgomery	55 min
May 15, 11:24 PM EDT	Areal Flood Advisory	PHI	Chester, Montgomery	116 min
May 15, 11:38 PM EDT	Areal Flood Warning	PHI	Chester, Montgomery	4 hr
May 16, 12:12 AM EDT	Areal Flood Advisory	PHI	Chester, Delaware, Montgomery	3 hr
May 16, 12:20 AM EDT	Special Weather Statement	PHI	Delaware, Philadelphia	55 min
May 16, 2:37 AM EDT	Areal Flood Warning	PHI	Philadelphia	3 hr
May 16, 4:27 AM EDT	Areal Flood Warning	PHI	Delaware	3 hr

Nearby

Flash Flood Warnings in Pennsylvania, 2012 Every flash flood warning in 2012

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.