Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 1994

Severe Thunderstorm Warning 68, NWS Philadelphia/Mount Holly

July 14, 1994Chester County, Pennsylvania

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Jul 14, 1994, 5:32 PM EDT for Chester County, Pennsylvania. It was in force for 43 min.

The area

The counties it named.

The facts

Issued
Jul 14, 1994, 5:32 PM EDT (21:32 UTC)
Expired
Jul 14, 1994, 6:15 PM EDT
In force
43 min
Issued by
NWS Philadelphia/Mount Holly
Area
Whole counties

County Chester County, PA

The nearest sounding before it

Atlantic City In, NJ (KACY), launched 12:00Z, 9.5 hours before the alert went out and 122 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 12:00Z on 1994-07-14Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 651 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Atlantic City In, NJ at 12:00Z on 1994-07-14The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 4 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
651 J/kg
Mixed-layer CIN
-31 J/kg
Mixed-layer LCL
1094 m above ground
0-6 km bulk shear
21 kt
0-1 km storm-relative helicity
4 m²/s²
0-3 km storm-relative helicity
75 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 142137
SVRPHL
PAC029-142215-
 
BULLETIN - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE PHILADELPHIA/MOUNT HOLLY NJ
532 PM EDT THU JUL 14 1994
 
THE NATIONAL WEATHER SERVICE IN PHILADELPHIA/MOUNT HOLLY HAS ISSUED A
SEVERE THUNDERSTORM WARNING EFFECTIVE UNTIL  615 PM EDT
FOR PEOPLE IN THE FOLLOWING LOCATION...
 
IN SOUTHEAST PENNSYLVANIA
 
   ...CHESTER COUNTY
 
 
NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A SEVERE THUNDERSTORM
OVER EASTERN LANCASTER WAS ABOUT TO MOVE INTO CHESTER COUNTY NEAR
ATGLEN AND WEST FALLOWFIELD.  THIS STORM WAS MOVING EAST AT ABOUT 25
MILES PER HOUR AND WITH THE PRESENT MOTION SHOULD PASS JUST TO THE
SOUTH OF COATESVILLE AND DOWNINGTOWN.
 
HEAVY RAINS WITH THIS THUNDERSTORM MAY CAUSE FLOODING OF SMALL
STREAMS AND UNDERPASSES VERY QUICKLY.  DO NOT DRIVE YOUR CAR INTO
AREAS WHERE THE WATER COVERS THE ROADWAY.  THE WATER MAY BE DEEPER
THAN YOU THINK.  IF CAUGHT IN RISING WATERS...ABANDON YOUR CAR
QUICKLY.  MOVE TO HIGHER GROUND.

What forecasters said that day

The local office's own words before this severe thunderstorm warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

In the hours before

Special weather statement, Jul 14, 1:28 PM EDT, 4 hours 4 minutes before
PAZ 048-054-055-058-060-061-062-142000-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE ALLENTOWN PA
130 PM EDT WED JUL 13 1994

...INTENSE THUNDERSTORMS MOVING INTO BERKS COUNTY...

AT 125 PM EDT NATIONAL WEATHER SERVICE RADAR WAS SHOWING A LINE
OF INTENSE THUNDERSTORMS MOVING INTO SOUTHERN BERKS COUNTY. THESE
STORMS ARE MOVING TO THE NORTHEAST AT 12 MPH. THESE STORMS COULD
PRODUCE DANGEROUS LIGHTNING...LOCALLY HEAVY RAINS...STRONG GUSTY
WINDS AND HAIL.

PERSONS SHOULD STAY TUNED TO NOAA WEATHER RADIO...LOCAL TELEVISION
AND RADIO STATIONS FOR FURTHER STATEMENTS ON THESE DEVELOPING
THUNDERSTORMS.

CPB
Special weather statement, Jul 14, 2:57 PM EDT, 2 hours 35 minutes before
PAZ067>071-NJZ015>019-142100-

SPECIAL WEATHER STATEMENT/SHORT TERM FORECAST
NATIONAL WEATHER SERVICE PHILADELPHIA/MOUNT HOLLY NJ
255 PM EDT THU JUL 14 1994

...LINE OF SHOWERS AND THUNDERSTORMS moving into northern portions of
the delaware valley...

DOPPLER RADAR SHOWED A LINE OF SHOWERS AND THUNDERSTORMS MOVING INTO
WESTERN BURLINGTON  AND INTO SOUTHERN MERCER COUNTIES IN NEW JERSEY. THE
LINE EXTENDED ACROSS THE DELAWARE INTO MONTGOMERY AND BUCKS COUNTIES IN
PENNSYLVANIA. SHOWERS LINGERED OVER PORTION OF CAMDEN COUNTY and the
city of philadelphia.

some of these showers were producing locally heavy rain in a relatively
short time. the heaviest rain was over southwest burlington county in
new jersey and over eastern philadelphia and bucks counties in
pennsylvania.

movement was to the northeast at aROUND 15 MPH AND THIS WILL CONTINUE TO
BRING THE LINE OF SHOWERS AND THUNDERSTORMS INTO northern bucks county
and southern mercer c(ounty in the next hour.

PERSONS SHOULD BE ALERT FOR THREATENING WEATHER AND HEAD INDOORS AT THE
FIRST SIGN OF THUNDERSTORMS.  IN ADDITION...MOTORISTS SHOULD BE WARY FOR
POOR DRAINAGE FLOODING AND PONDING ON ROADWAYS.

wally
Special weather statement, Jul 14, 3:23 PM EDT, 2 hours 9 minutes before
PAZ 048-054-055-058-060-061-062-142300-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE ALLENTOWN PA
320 PM EDT WED JUL 13 1994

...THUNDERSTORMS MOVING ACROSS EAST CENTRAL PENNSYLVANIA...

AT 315 PM EDT NATIONAL WEATHER SERVICE RADAR WAS SHOWING AN AREA
OF THUNDERSTORMS AND SHOWERS SPREADING OVER ALL OF THE LEHIGH VALLEY
AND POCONOS REGIONS OF EAST CENTRAL PENNSYVANIA. THESE STORMS COULD
PRODUCE DANGEROUS LIGHTNING...LOCALLY HEAVY RAINS...STRONG GUSTY
WINDS AND HAIL. THESE STORMS WILL CONTINUE TO DEVELOP AND MOVE
NORTHEAST ACROSS THE AREA AT 15 MPH.

PERSONS SHOULD STAY TUNED TO NOAA WEATHER RADIO...LOCAL TELEVISION
AND RADIO STATIONS FOR FURTHER STATEMENTS ON THESE DEVELOPING
THUNDERRSTORMS.

CPB
Special weather statement, Jul 14, 4:38 PM EDT, 54 minutes before
PAZ 048-054-055-058-060-061-062-142300-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE ALLENTOWN PA
438 PM EDT WED JUL 13 1994

...THUNDERSTORMS MOVING ACROSS EAST CENTRAL PENNSYLVANIA...

AT 335 PM EDT NATIONAL WEATHER SERVICE RADAR WAS SHOWING AN AREA
OF THUNDERSTORMS AND SHOWERS SPREADING OVER ALL OF THE LEHIGH VALLEY
AND POCONOS REGIONS OF EAST CENTRAL PENNSYVANIA. THESE STORMS COULD
PRODUCE DANGEROUS LIGHTNING...LOCALLY HEAVY RAINS...STRONG GUSTY
WINDS AND HAIL. THESE STORMS WILL CONTINUE TO DEVELOP AND MOVE
NORTHEAST ACROSS THE AREA AT 15 MPH. SOME STREET AND FLOODING OF
LOW LYING AREAS IS POSSIBLE THIS EVENING AND NIGHT.

PERSONS SHOULD STAY TUNED TO NOAA WEATHER RADIO...LOCAL TELEVISION
AND RADIO STATIONS FOR FURTHER STATEMENTS ON THESE DEVELOPING
THUNDERSTORMS.

CPB
Special weather statement, Jul 14, 5:30 PM EDT, 2 minutes before
NJZ019>026-501-142130-

SPECIAL WEATHER STATEMENT...THUNDERSTORMS
NATIONAL WEATHER SERVICE ATLANTIC CITY NJ
530 PM EDT THU JUL 14 1994

AT 530 PM...ATLANTIC CITY WEATHER RADAR SHOWED A BROAD AREA OF THUNDERSTORMS
FROM NORTHERN MARYLAND THROUGH MUCH OF EASTERN PENNSYLVANIA INCLUDING THE
PHILADELPHIA VICINITY TO NORTHERN AND CENTRAL NEW JERSEY.

WHILE THESE STORMS HAVE BEEN STAYING TO THE NORTH OF THE SOUTH JERSEY
AREA...NEW THUNDERSTORM DEVELOPMENT IN NORTHERN MARYLAND...NORTHERN DELEWARE
AND SOUTHEASTERN PENNSYLVANIA WILL MOVE MORE EASTWARD THAN PREVIOUS
THUNDERSTORMS...AND COULD POSE A THREAT FOR SOUTHEASTERN NEW JERSEY
AFTER 8 PM THIS EVENING.

ANY OF THESE THUNDERSTORMS CAN PRODUCE VERY HEAVY DOWNPOURS...FREQUENT CLOUD
TO GROUND LIGHTNING...WIND GUSTS PAST 50 MPH AND PERHAPS HAIL.

TRM
Special weather statement, Jul 14, 5:30 PM EDT, 2 minutes before
PAZ067>071-NJZ015>019-142330-

SPECIAL WEATHER STATEMENT/SHORT TERM FORECAST
NATIONAL WEATHER SERVICE PHILADELPHIA/MOUNT HOLLY NJ
530 PM EDT THU JUL 14 1994

...SHOWERS AND THUNDERSTORMS CONTINUING ACROSS PHILADELPHIA AND THE
NORTHWESTERN SUBURBS...

DOPPLER RADAR SHOWED A VERY STRONG THUNDERSTORM OVER CENTRAL LANCASTER
COUNTY JUST TO THE SOUTHEAST OF LANCASTER CITY.  IT WAS MOVING EAST
AT ABOUT 15 MILES AN HOUR AND SHOULD MOVE INTO CHESTER COUNTY BETWEEN
535 AND 550 PM.

DOPPLER RADAR SHOWED NUMEROUS SHOWERS AND THUNDERSTORMS OVER MOST OF
THE NORTHERN HALF OF CHESTER COUNTY AS WELL AS MOST OF MERCER...BUCKS
AND MONTGOMERY COUNTIES.  WHILE THE THUNDERSTORMS WERE SHOWING SIGNS OF
LOSING THEIR SEVERE CHARACTERISTICS...THEY STILL HAVE BEEN PROLIFIC RAIN
PRODUCERS DROPPING A DOPPLER ESTIMATED 1 TO 1.5 INCHES OF RAIN PER HOUR.
THESE STORMS SHOULD CONTINUE TO AFFECT PHILADELPHIA AND THE NEARBY
NORTHERN AND WESTERN SUBURBS DURING THE NEXT HOUR OR TWO.

PERSONS SHOULD BE ALERT FOR THREATENING WEATHER AND HEAD INDOORS AT THE
FIRST SIGN OF THUNDERSTORMS.  IN ADDITION...MOTORISTS SHOULD BE WARY FOR
POOR DRAINAGE FLOODING AND PONDING ON ROADWAYS.  NEVER ATTEMPT TO DRIVE
ACROSS A FLOODED: ROADWAY.  MORE PERSONS ARE KILLED EACH YEAR FROM
FLOODING THAN ANY OTHER METEOROLOGICAL PHENOMENA.

GIGI

The office that day

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

IssuedProductOfficeCountiesLasted
Jul 14, 3:51 PM EDTSevere Thunderstorm WarningPHIChester54 min
Jul 14, 3:59 PM EDTTornado WarningPHIChester46 min
Jul 14, 4:26 PM EDTSevere Thunderstorm WarningPHIDelaware49 min

Nearby

Severe Thunderstorm Warnings in Pennsylvania, 1994Every severe thunderstorm warning in 1994

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.