Alert archive / Pennsylvania / Flash Flood Warnings in 2014

Flash Flood Warning 30, NWS Philadelphia/Mount Holly

July 10, 2014Chester County, Pennsylvania

NWS Philadelphia/Mount Holly issued this flash flood warning at Jul 10, 2014, 9:48 PM EDT for Chester County, Pennsylvania. It was in force for 3 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: Jul 10, 2014, 9:48 PM EDT (01:48 UTC)
Expired: Jul 11, 2014, 12:45 AM EDT
In force: 3 hr
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Flood severity: None

County Chester County, PA

The radar

The Philadelphia radar (KDIX), 122 km from the middle of the area, began a volume at 01:51 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
Jul 10, 11:30 PM EDT	FLASH FLOOD	Downingtown, PA	FLOODING ALONG GREEN STREET IN DOWNINGTOWN. CAR STALLED OUT TRYING TO DRIVE THROUGH THE HIGH WATER.

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, 1.8 hours before the alert went out and 180 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: 301 J/kg
Mixed-layer CIN: -51 J/kg
Mixed-layer LCL: 946 m above ground
0-6 km bulk shear: 28 kt
0-1 km storm-relative helicity: 10 m²/s²
0-3 km storm-relative helicity: -4 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.

096 
WGUS51 KPHI 110148
FFWPHI
PAC029-110445-
/O.NEW.KPHI.FF.W.0030.140711T0148Z-140711T0445Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
948 PM EDT THU JUL 10 2014

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

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

* UNTIL 1245 AM EDT

* AT 947 PM EDT...FLASH FLOODING WAS REPORTED FROM A THUNDERSTORM
  OVER THE WARNED AREA.

* LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO
  DOWNINGTOWN...LIONVILLE...HONEY BROOK...GLENMOORE AND CHESTER
  SPRINGS

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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.

BE ESPECIALLY CAUTIOUS AT NIGHT WHEN IT IS HARDER TO RECOGNIZE THE
DANGERS OF FLOODING. IF FLASH FLOODING IS OBSERVED ACT QUICKLY. MOVE
UP TO HIGHER GROUND TO ESCAPE FLOOD WATERS. DO NOT STAY IN AREAS
SUBJECT TO FLOODING WHEN WATER BEGINS RISING.

&&

LAT...LON 3999 7598 4004 7594 4011 7594 4013 7552
      3996 7548 3994 7600

$$

HEAVENER

3 follow-up statements

769 
WGUS71 KPHI 110152
FFSPHI

FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
952 PM EDT THU JUL 10 2014

PAC029-110445-
/O.CON.KPHI.FF.W.0030.000000T0000Z-140711T0445Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
CHESTER PA-
952 PM EDT THU JUL 10 2014

...A FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 1245 AM EDT FOR
CENTRAL CHESTER COUNTY...

AT 949 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A 
THUNDERSTORM PRODUCING FLASH FLOODING OVER THE WARNED AREA.

LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO LIONVILLE...
HONEY BROOK...GLENMOORE AND CHESTER SPRINGS

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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.

BE ESPECIALLY CAUTIOUS AT NIGHT WHEN IT IS HARDER TO RECOGNIZE THE
DANGERS OF FLOODING. IF FLASH FLOODING IS OBSERVED ACT QUICKLY. MOVE
UP TO HIGHER GROUND TO ESCAPE FLOOD WATERS. DO NOT STAY IN AREAS
SUBJECT TO FLOODING WHEN WATER BEGINS RISING.

&&

LAT...LON 3999 7598 4004 7594 4011 7594 4013 7552
      3996 7548 3994 7600

$$

HEAVENER

574 
WGUS71 KPHI 110227
FFSPHI

FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1027 PM EDT THU JUL 10 2014

PAC029-110445-
/O.CON.KPHI.FF.W.0030.000000T0000Z-140711T0445Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
CHESTER PA-
1027 PM EDT THU JUL 10 2014

...A FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 1245 AM EDT FOR
CENTRAL CHESTER COUNTY...

AT 1022 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR CONTINUED TO 
INDICATE AN AREA OF SLOW MOVING SHOWERS AND THUNDERSTORMS PRODUCING 
HEAVY RAIN IN THE AREA. THESE ARE DRIFTING SOUTHEASTWARD.

DOPPLER RADAR ESTIMATES INDICATE THAT 2 TO 3 INCHES OF RAIN HAS 
ALREADY FALLEN. THE HEAVIEST RAIN AS OF 1025 PM HAS FALLEN FROM 
ABOUT THE EXTON, DOWNINGTOWN AND THORNDALE AREAS.

LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO 
LIONVILLE...HONEY BROOK...GLENMOORE AND CHESTER SPRINGS.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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.

BE ESPECIALLY CAUTIOUS AT NIGHT WHEN IT IS HARDER TO RECOGNIZE THE
DANGERS OF FLOODING. IF FLASH FLOODING IS OBSERVED ACT QUICKLY. MOVE
UP TO HIGHER GROUND TO ESCAPE FLOOD WATERS. DO NOT STAY IN AREAS
SUBJECT TO FLOODING WHEN WATER BEGINS RISING.

A FLASH FLOOD WARNING MEANS THAT FLOODING IS IMMINENT OR OCCURRING.
IF YOU ARE IN THE WARNING AREA MOVE TO HIGHER GROUND IMMEDIATELY.
RESIDENTS LIVING ALONG STREAMS AND CREEKS SHOULD TAKE IMMEDIATE
PRECAUTIONS TO PROTECT LIFE AND PROPERTY. DO NOT ATTEMPT TO CROSS
SWIFTLY FLOWING WATERS OR WATERS OF UNKNOWN DEPTH BY FOOT OR BY
AUTOMOBILE.

&&

LAT...LON 3999 7598 4004 7594 4011 7594 4013 7552
      3996 7548 3994 7600

$$

GORSE

768 
WGUS71 KPHI 110418
FFSPHI

FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1218 AM EDT FRI JUL 11 2014

PAC029-110427-
/O.CAN.KPHI.FF.W.0030.000000T0000Z-140711T0445Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
CHESTER PA-
1218 AM EDT FRI JUL 11 2014

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

SOME LIGHT RAIN REMAINS, HOWEVER THE EARLIER HEAVY RAIN HAS SHIFTED 
SOUTH AND IS WEAKENING. ANY RESIDUAL RUNOFF AND POOR DRAINAGE 
FLOODING WILL CONTINUE TO DIMINISH. THEREFORE, THE FLASH FLOOD 
WARNING IS CANCELLED.

LAT...LON 3999 7598 4004 7594 4011 7594 4013 7552
      3996 7548 3994 7600

$$

GORSE

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 10, 9:19 PM EDT	Areal Flood Advisory	PHI	Chester	3 hr
Jul 10, 11:17 PM EDT	Areal Flood Advisory	PHI	Chester	118 min
Jul 11, 12:55 AM EDT	River Flood Warning	PHI	Chester	7 hr

Nearby

Flash Flood Warnings in Pennsylvania, 2014 Every flash flood warning in 2014

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.