Alert archive / Pennsylvania / Flash Flood Warnings in 2001

Flash Flood Warning 54, NWS Philadelphia/Mount Holly

August 12, 2001Chester County, Pennsylvania

NWS Philadelphia/Mount Holly issued this flash flood warning at Aug 12, 2001, 6:57 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 counties it named.

The facts

Issued: Aug 12, 2001, 6:57 PM EDT (22:57 UTC)
Expired: Aug 12, 2001, 9:00 PM EDT
In force: 2 hr
Issued by: NWS Philadelphia/Mount Holly
Area: Whole counties

County Chester County, PA

The radar

The Philadelphia radar (KDIX), 114 km from the middle of the area, began a volume at 22:57 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 12:00Z, 11.0 hours before the alert went out and 182 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: 1033 J/kg
Mixed-layer CIN: -34 J/kg
Mixed-layer LCL: 508 m above ground
0-6 km bulk shear: 15 kt
0-1 km storm-relative helicity: 33 m²/s²
0-3 km storm-relative helicity: 43 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 122301
FFWPHI
PAC029-130100-

BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
657 PM EDT SUN AUG 12 2001

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

* FLASH FLOOD WARNING FOR...
  NORTHERN CHESTER COUNTY IN SOUTHEAST PENNSYLVANIA

* UNTIL 900 PM EDT.

* AT 651 PM EDT...WEATHER SERVICE RADAR INDICATED RAINFALL AMOUNTS 
  UP TO 2.5 INCHES DURING THE PAST HOUR.  MORE HEAVY RAIN IS 
  EXPECTED OVER NORTHERN CHESTER COUNTY DURING THE NEXT HOUR OR SO.

THE HEAVIEST RAIN IS ROUGHLY ALONG A LINE FROM HONEY BROOK TO JUST 
WEST OF ROYERSFORD IN MONTGOMERY COUNTY.

BE ESPECIALLY CAUTIOUS AT NIGHT WHEN IT IS HARDER TO RECOGNIZE THE
DANGERS OF FLOODS AND FLASH FLOODS. 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 OCCURRING OR IS
IMMINENT. MOST FLASH FLOOD DEATHS OCCUR IN AUTOMOBILES. 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. VEHICLES
CAUGHT IN RISING WATER SHOULD BE ABANDONED QUICKLY. MOVE TO HIGHER
GROUND.

FOR THE LATEST STORM INFORMATION...PLEASE TUNE TO NOAA WEATHER
RADIO...YOUR LOCAL RADIO OR TELEVISION STATION...OR YOUR CABLE
TELEVISION OUTLET.

$$

LAT...LON 4025 7568 4010 7546 3988 7601 4011 7594

AMC

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 12, 6:21 PM EDT	Flash Flood Warning	PHI	Montgomery	3 hr

Nearby

Flash Flood Warnings in Pennsylvania, 2001 Every flash flood warning in 2001

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.