Alert archive / Maryland / Flash Flood Warnings in 2010

Flash Flood Warning 1, NWS Philadelphia/Mount Holly

March 29, 2010Cecil County, Maryland; Chester County, Pennsylvania; New Castle County, Delaware

NWS Philadelphia/Mount Holly issued this flash flood warning at Mar 29, 2010, 1:28 AM EDT for Cecil County, Maryland; Chester County, Pennsylvania; New Castle County, Delaware. It was in force for 4 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: Mar 29, 2010, 1:28 AM EDT (05:28 UTC)
Expired: Mar 29, 2010, 5:41 AM EDT
In force: 4 hr
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Flood severity: None

Counties New Castle County, DE, Cecil County, MD, Chester County, PA

The radar

The Philadelphia radar (KDIX), 108 km from the middle of the area, began a volume at 05:27 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

Washington/Dulle, VA (KIAD), launched 00:00Z, 5.5 hours before the alert went out and 181 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 637 m above ground
0-6 km bulk shear: 65 kt
0-1 km storm-relative helicity: 502 m²/s²
0-3 km storm-relative helicity: 939 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.

540 
WGUS51 KPHI 290528
FFWPHI
DEC003-MDC015-PAC029-291030-
/O.NEW.KPHI.FF.W.0001.100329T0528Z-100329T1030Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
128 AM EDT MON MAR 29 2010

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

* FLASH FLOOD WARNING FOR...
  NORTHERN CECIL COUNTY IN NORTHEAST MARYLAND...
  NORTHERN NEW CASTLE COUNTY IN NORTHERN DELAWARE...
  THIS INCLUDES THE CITIES OF...WILMINGTON...NEWARK...
  CHESTER COUNTY IN SOUTHEAST PENNSYLVANIA...
  THIS INCLUDES THE CITY OF WEST CHESTER...

* UNTIL 630 AM EDT

* AT 120 AM EDT...NATIONAL WEATHER SERVICE RADAR INDICATED FLASH 
  FLOODING WAS IMMINENT FROM AREAS OF PERSISTENT HEAVY RAIN OVER THE
  WARNED AREA. VALLEY CREEK AT VALLEY FORGE WAS RISING RAPIDLY...AND
  WILL FLOOD DURING THE NEXT 90 MINUTES. RADAR IMAGERY INDICATED
  THAT HEAVY RAIN WILL CONTINUE OVER THIS AREA FOR THE EARLY PART OF
  THE OVERNIGHT PERIOD.

* LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO KENNETT
  SQUARE...COCHRANVILLE...CHESTER SPRINGS...PAOLI...MARSHALLTON...
  LIONVILLE...DOWNINGTOWN AND COATESVILLE.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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.

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 4001 7584 4018 7560 4009 7550 4003 7545
      3986 7564 3980 7545 3967 7558 3963 7575
      3962 7612

$$

1 follow-up statement

767 
WGUS71 KPHI 290941
FFSPHI

FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
541 AM EDT MON MAR 29 2010

DEC003-MDC015-PAC029-290949-
/O.CAN.KPHI.FF.W.0001.000000T0000Z-100329T1030Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
CECIL MD-CHESTER PA-NEW CASTLE DE-
541 AM EDT MON MAR 29 2010

...THE FLASH FLOOD WARNING HAS BEEN CANCELLED FOR NORTHERN NEW
CASTLE...CHESTER AND NORTHERN CECIL COUNTIES...

ALTHOUGH SOME STREAMS ARE STILL RUNNING HIGH FROM RAIN DURING THE 
OVERNIGHT HOURS, INCLUDING THE CHRISTINA RIVER WHICH REMAINS ABOVE 
FLOOD STAGE AT COOCHS BRIDGE...THE THREAT OF FLASH FLOODING HAS 
ENDED FOR THE TIME BEING. THE FLASH FLOOD WARNING HAS THEREFORE
BEEN CANCELLED.

LAT...LON 4001 7584 4018 7560 4009 7550 4003 7545
      3986 7564 3980 7545 3967 7558 3963 7575
      3962 7612

$$

JJM

The office that day

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

Issued	Product	Office	Counties	Lasted
Mar 29, 3:43 AM EDT	Areal Flood Warning	PHI	Caroline, Queen Anne's, Talbot	25 hr
Mar 29, 12:56 AM EDT	Areal Flood Advisory	PHI	Chester, Delaware, Montgomery, Philadelphia	4 hr
Mar 29, 3:26 AM EDT	River Flood Warning	PHI	Delaware	2 hr
Mar 29, 4:59 AM EDT	Areal Flood Advisory	PHI	Bucks, Delaware, Montgomery, Philadelphia	6 hr
Mar 29, 2:15 AM EDT	River Flood Warning	PHI	New Castle	5 hr
Mar 29, 3:04 PM EDT	Coastal Flood Warning	PHI	Kent, Sussex	20 hr

Nearby

Flash Flood Warnings in Maryland, 2010 Flash Flood Warnings in Pennsylvania, 2010 Flash Flood Warnings in Delaware, 2010 Every flash flood warning in 2010

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.