Alert archive / Pennsylvania / Flash Flood Warnings in 1989

Flash Flood Warning 36, NWS Philadelphia/Mount Holly

September 20, 1989Montgomery County, Pennsylvania

NWS Philadelphia/Mount Holly issued this flash flood warning at Sep 20, 1989, 7:42 AM EDT for Montgomery County, Pennsylvania. It was in force for 3 hr.

The area

The counties it named.

The facts

Issued
Sep 20, 1989, 7:42 AM EDT (11:42 UTC)
Expired
Sep 20, 1989, 10:45 AM EDT
In force
3 hr
Issued by
NWS Philadelphia/Mount Holly
Area
Whole counties

County Montgomery County, PA

The radar

The WSR-88D network and its archive begin in 1991, so there is no radar volume for this alert.

The nearest sounding before it

Atlantic City In, NJ (KACY), launched 00:00Z, 11.7 hours before the alert went out and 112 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, Atlantic City In, NJ at 00:00Z on 1989-09-20Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 884 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, Atlantic City In, NJ at 00:00Z on 1989-09-20The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 73 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
884 J/kg
Mixed-layer CIN
-11 J/kg
Mixed-layer LCL
549 m above ground
0-6 km bulk shear
18 kt
0-1 km storm-relative helicity
73 m²/s²
0-3 km storm-relative helicity
82 m²/s²
Significant tornado parameter
0.0
Supercell composite
1.2

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

000 
TTAA00 KPHL 201142
FFWPHL
PAC091-201445-

BULLETIN - IMMEDIATE BROADCAST REQUESTED/EBS ACTIVATION REQUESTED 
URBAN AND SMALL STREAM FLOOD WARNING 
NATIONAL WEATHER SERVICE PHILADELPHIA PA
742 AM EDT WED SEP 20 1989

THE NATIONAL WEATHER SERVICE HAS ISSUED A URBAN AND SMALL 
STREAM FLOOD WARNING EFFECTIVE UNTIL 1045 AM EDT FOR PEOPLE IN 
THE FOLLOWING COUNTY

   IN THE SOUTHEAST PART OF PENNSYLVANIA
      MONTGOMERY

HEAVY RAIN OF 4 TO 4.5 INCHES SINCE TUESDAY MORNING HAVE FALLEN
OVER THE PERKIOMEN CREEK. THE STREAM LEVEL WAS AT 6 FEET WITH
A FLOOD STAGE OF 11 FEET. THE PERKIOMEN CREEK ROSE 2 FEET BETWEEN
725 AND 740 AM AND IS EXPECTED TO GO OVER FLOOD STAGE BY 830 AM.

IF YOU ARE IN THE WARNED COUNTY IN AN AREA SUBJECT TO FLOODING
MOVE TO HIGHER GROUND. DO NOT DRIVE THROUGH FLOOD WATERS. CLIMBING
ATOP YOUR STALLED VEHICLE WILL NOT PREVENT YOU FROM BEING SWEPT
INTO DANGEROUS STREAM CONDITIONS AS WATER LEVELS RISE.

 A SMALL STREAM AND URBAN FLOOD WATCH REMAIN IN EFFECT FOR THE
 LOWER SUSQUEHANNA VALLEY...THE POCONOS...THE EAST CENTRAL AREA
 AND SOUTHEAST PENNSYLVANIA.

 RNS

The office that day

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

IssuedProductOfficeCountiesLasted
Sep 20, 8:14 AM EDTFlash Flood WarningPHIBucks3 hr
Sep 20, 2:33 PM EDTFlash Flood WarningPHIBucks, Montgomery3 hr
Sep 20, 6:30 PM EDTFlash Flood WarningPHIBucks, Montgomery3 hr

Nearby

Flash Flood Warnings in Pennsylvania, 1989Every flash flood warning in 1989

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.