Alert archive / Pennsylvania / Flash Flood Warnings in 1990

Flash Flood Warning 4, NWS Philadelphia/Mount Holly

June 9, 1990Montgomery County, Pennsylvania

NWS Philadelphia/Mount Holly issued this flash flood warning at Jun 9, 1990, 2:33 AM EDT for Montgomery County, Pennsylvania. It was in force for 57 min.

The area

The counties it named.

The facts

Issued
Jun 9, 1990, 2:33 AM EDT (06:33 UTC)
Expired
Jun 9, 1990, 3:30 AM EDT
In force
57 min
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, 6.6 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 1990-06-09Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 7 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 1990-06-09The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 139 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
7 J/kg
Mixed-layer CIN
-317 J/kg
Mixed-layer LCL
1171 m above ground
0-6 km bulk shear
44 kt
0-1 km storm-relative helicity
139 m²/s²
0-3 km storm-relative helicity
193 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.5

Open this sounding in Storm Lab

The text

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

000 
TTAA00 KPHL 090634
FFWPHL
PAC091-090730-
 
BULLETIN - EBS ACTIVATION REQUESTED
SEVERE THUNDERSTORM AND URBAN AND SMALL STREAM FLOOD WARNING
NATIONAL WEATHER SERVICE PHILADELPHIA PA
233 AM EDT SAT JUN 9 1990
 
THE NATIONAL WEATHER SERVICE IN PHILADELPHIA HAS ISSUED A
SEVERE THUNDERSTORM AND FLASH FLOOD WARNING
EFFECTIVE UNTIL  330 AM EDT
FOR PEOPLE IN THE FOLLOWING LOCATION...
 
IN SOUTHEAST PENNSYLVANIA
 
   ...MONTGOMERY COUNTY
 
NATIONAL WEATHER SERVICE RADAR SHOWED A POTENTIALLY SEVERE
THUNDERSTORM OVER EASTERN CHESTER COUNTY AT 230 AM EDT. THE
THUNDERSTORM WAS MOVING EAST AT 45 MPH AND WILL MOVE INTO
MONTGOMERY COUNTY BY 240 AM. AROUND 145 AM THIS
THUNDERSTORM PRODUCED GOLFBALL SIZE HAIL IN COATESVILLE IN
CHESTER COUNTY.
 
THIS IS A DANGEROUS STORM.  IF YOU ARE IN THE WARNED AREA...PREPARE
FOR STRONG DAMAGING WINDS...LARGE HAIL...VERY HEAVY RAIN AND DEADLY
LIGHTNING.  SHOULD THE STORM APPROACH YOU...SEEK IMMEDIATE SHELTER
INDOORS...BUT DO NOT STAND NEAR WINDOWS.  MOBILE HOMES ARE MOST
VULNERABLE TO HIGH WINDS AND SHOULD BE AVOIDED.
 
HEAVY RAINS WITH THIS THUNDERSTORM MAY CAUSE FLOODING OF SMALL
STREAMS AND UNDERPASSES VERY QUICKLY.  DO NOT DRIVE YOUR CAR INTO
AREAS WHERE THE WATERa COVERS THE ROADWAY.  THE WATER MAY BE DEEPER
THAN YOU THINK.  IF CAUGHT IN RISING WATERS...ABANDON YOUR CAR
QUICKLY.  MOVE TO HIGHER GROUND.
 
STAUBER

The office that day

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

IssuedProductOfficeCountiesLasted
Jun 9, 12:50 AM EDTSevere Thunderstorm WarningPHIChester, Delaware, Philadelphia3 hr
Jun 9, 1:50 AM EDTFlash Flood WarningPHIChester, Delaware, Philadelphia115 min
Jun 9, 2:33 AM EDTSevere Thunderstorm WarningPHIMontgomery57 min

Nearby

Flash Flood Warnings in Pennsylvania, 1990Every flash flood warning in 1990

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.