Alert archive / Pennsylvania / Flash Flood Warnings in 1998

Flash Flood Warning 15, NWS Philadelphia/Mount Holly

May 8, 1998Montgomery County, Pennsylvania

NWS Philadelphia/Mount Holly issued this flash flood warning at May 8, 1998, 9:12 PM EDT for Montgomery County, Pennsylvania. It was in force for 5 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
May 8, 1998, 9:12 PM EDT (01:12 UTC)
Expired
May 9, 1998, 2:00 AM EDT
In force
5 hr
Issued by
NWS Philadelphia/Mount Holly
Area
Whole counties

County Montgomery County, PA

The radar

The Philadelphia radar (KDIX), 86 km from the middle of the area, began a volume at 01:11 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, 1.2 hours before the alert went out and 224 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 1998-05-09Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 102 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 1998-05-09The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -22 square meters per square second.1939Sfc1 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
102 J/kg
Mixed-layer CIN
-8 J/kg
Mixed-layer LCL
542 m above ground
0-6 km bulk shear
6 kt
0-1 km storm-relative helicity
-22 m²/s²
0-3 km storm-relative helicity
30 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 090118 COR
FFWPHL
PAC091-090600-

BULLETIN - EAS ACTIVATION REQUESTED...COR FOR LOCN/EXP TIME
FLOOD WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
912 PM EDT FRI MAY 8 1998

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A 

* FLOOD WARNING FOR...
  CENTRAL MONTGOMERY COUNTY IN PENNSYLVANIA
  
* UNTIL 200 AM EDT

*
* (AT 9 PM EDT THE PERKIOMEN CREEK IN SCHWENKSVILLE HAS REACHED
   A STAGE OF 7.2 FEET.  FLOOD STAGE IS 7.0 FEET.

  SOME MINOR FLOODING CAN BE EXPECTED IN LOW LYING AREAS ALONG THE
  PERKIOMEN CREEK AND ITS TRIBUTARIES THROUGH MIDNIGHT.  THE CREEK
  AT GRATERFORD IS CURRENTLY AT 7.3 FEET AND IS EXPECTED TO CREST
  BETWEEN 8 AND 9 FEET BEFORE DAYBREAK SATURDAY.  FLOOD STAGE AT
  GRATERFORD IS 11 FEET.

  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 FLOOD WATERS. 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.

  TFG/NC

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.