Alert archive / Pennsylvania / Flash Flood Warnings in 1998

Flash Flood Warning 8, NWS Philadelphia/Mount Holly

April 1, 1998Chester County, Montgomery County, Pennsylvania

NWS Philadelphia/Mount Holly issued this flash flood warning at Apr 1, 1998, 6:20 PM EST for Chester County, Montgomery County, Pennsylvania. It was in force for 3 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
Apr 1, 1998, 6:20 PM EST (23:20 UTC)
Expired
Apr 1, 1998, 9:20 PM EST
In force
3 hr
Issued by
NWS Philadelphia/Mount Holly
Area
Whole counties

Counties Chester County, PA, Montgomery County, PA

The radar

The Philadelphia radar (KDIX), 99 km from the middle of the area, began a volume at 23:23 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

Phillips Aaf/Abe, MD (KAPG), launched 12:00Z, 11.3 hours before the alert went out and 83 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, Phillips Aaf/Abe, MD at 12:00Z on 1998-04-01Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 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, Phillips Aaf/Abe, MD at 12:00Z on 1998-04-01The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 179 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
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
1059 m above ground
0-6 km bulk shear
28 kt
0-1 km storm-relative helicity
179 m²/s²
0-3 km storm-relative helicity
141 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 012319
FFWPHL
PAC029-091-020220-

BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
620 PM EST WED APR 1 1998

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY HAS ISSUED A
FLASH FLOOD WARNING EFFECTIVE UNTIL 920 PM EST
FOR PEOPLE IN THE FOLLOWING LOCATIONS...

IN PENNSYLVANIA

   ...EASTERN CHESTER COUNTY
   ...SOUTHEASTERN AND CENTRAL MONTGOMERY COUNTY

NATIONAL WEATHER SERVICE RADAR INDICATED UPWARDS OF 3 INCHES OF
RAIN HAD FALLEN ACROSS PARTS OF MONTGOMERY AND EASTERN CHESTER
COUNTY LATE THIS AFTERNOON...AND THE VALLEY CREEK NEAR VALLEY FORGE
HAD RISEN TO A STAGE OF 7 FEET AS OF 6 PM. MORE RAIN IS POSSIBLE IN
THE WARNING AREA THROUGH THE EARLY EVENING.

A FLOOD WARNING REMAINS IN EFFECT FOR THE REST OF CHESTER COUNTY
UNTIL 640 PM THIS EVENING.

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

KRAUS

The office that day

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

IssuedProductOfficeCountiesLasted
Apr 1, 2:23 PM ESTSevere Thunderstorm WarningPHIChester32 min
Apr 1, 3:38 PM ESTFlash Flood WarningPHIChester3 hr
Apr 1, 6:46 PM ESTSevere Thunderstorm WarningPHIBucks34 min

Nearby

Flash Flood Warnings in Pennsylvania, 1998Every flash flood warning in 1998

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.