Alert archive / Pennsylvania / Flash Flood Warnings in 1999

Flash Flood Warning 27, NWS Philadelphia/Mount Holly

August 26, 1999Chester County, Pennsylvania

NWS Philadelphia/Mount Holly issued this flash flood warning at Aug 26, 1999, 11:00 PM EDT for Chester County, Pennsylvania. 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 counties it named.

The facts

Issued
Aug 26, 1999, 11:00 PM EDT (03:00 UTC)
Expired
Aug 27, 1999, 3:00 AM EDT
In force
4 hr
Issued by
NWS Philadelphia/Mount Holly
Area
Whole counties

County Chester County, PA

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 00:00Z, 3.0 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-pSkew-T log-p diagram, Washington/Dulle, VA at 00:00Z on 1999-08-27Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 31 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Washington/Dulle, VA at 00:00Z on 1999-08-27The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -30 square meters per square second.193958Sfc1 km3 km6 km9 kmRMLM
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
31 J/kg
Mixed-layer CIN
-245 J/kg
Mixed-layer LCL
1096 m above ground
0-6 km bulk shear
43 kt
0-1 km storm-relative helicity
-30 m²/s²
0-3 km storm-relative helicity
5 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 
TTAA00 KPHL 270305
FFWPHL

PAC029-270700-

BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1100 PM EDT THU AUG 26 1999

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

* FLASH FLOOD WARNING FOR...
  EASTERN CHESTER COUNTY IN PENNSYLVANIA.

* UNTIL 300 AM EDT.

* AT 1100 PM...THE VALLEY CREEK AT VALLEY FORGE WAS NEARING ITS
FLOOD STATE OF 7 FEET.  THE CREEK SHOULD SPILL OUT OF ITS BANKS
BETWEEN 1100 AND 1130 PM...RESULTING IN MINOR FLOODING IN ITS
VICINITY.  WITH THE HEAVIEST OF THE RAIN MOVING TO THE EAST...THE
CREEK SHOULD RETURN WITHIN ITS BANKS BY DAYBREAK.

RAINFALL AMOUNTS IN THE COUNTY RANGED AS HIGH AS TWO TO THREE
INCHES.  THIS RESULTED IN FLOODING IN AREAS OF POOR DRAINING AS
WELL.

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

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

.END
IOVINO/NATIONAL WEATHER SERVICE


&

Nearby

Flash Flood Warnings in Pennsylvania, 1999Every flash flood warning in 1999

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.