Alert archive / Pennsylvania / Flash Flood Warnings in 2004

Flash Flood Warning 88, NWS Philadelphia/Mount Holly

September 18, 2004Chester County, Delaware County, Pennsylvania

NWS Philadelphia/Mount Holly issued this flash flood warning at Sep 18, 2004, 10:31 AM EDT for Chester County, Delaware 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 outline as issued.

The facts

Issued
Sep 18, 2004, 10:31 AM EDT (14:31 UTC)
Expired
Sep 18, 2004, 1:30 PM EDT
In force
3 hr
Issued by
NWS Philadelphia/Mount Holly
Area
Counties, with a storm outline in the text

Counties Chester County, PA, Delaware County, PA

The radar

The Philadelphia radar (KDIX), 104 km from the middle of the area, began a volume at 14:31 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 12:00Z, 2.5 hours before the alert went out and 184 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 12:00Z on 2004-09-18Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 2 joules per kilogram.LCLEL10008507005003002001001 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, Washington/Dulle, VA at 12:00Z on 2004-09-18The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 14 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
2 J/kg
Mixed-layer CIN
0 J/kg
Mixed-layer LCL
498 m above ground
0-6 km bulk shear
4 kt
0-1 km storm-relative helicity
14 m²/s²
0-3 km storm-relative helicity
166 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 
WGUS51 KPHI 181432
FFWPHI
PAC029-045-181730-
/X.NEW.KPHI.FF.W.0008.040918T1431Z-040918T1730Z/
/0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1031 AM EDT SAT SEP 18 2004

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

* FLASH FLOOD WARNING FOR...
  CHESTER COUNTY IN SOUTHEAST PENNSYLVANIA
  DELAWARE COUNTY IN SOUTHEAST PENNSYLVANIA

* UNTIL 130 PM EDT

* AT 1026 AM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
  UP TO 3 INCHES OF RAIN HAD FALLEN OVER EXTREME SOUTHEASTERN        
  PENNSYLVANIA SINCE EARLY THIS MORNING. ADDITIONAL RAIN IS          
  FORECAST UNTIL ABOUT NOON.

EXCESSIVE RUNOFF FROM HEAVY RAINFALL WILL CAUSE FLOODING OF SMALL 
CREEKS AND STREAMS...HIGHWAYS AND UNDERPASSES. ADDITIONALLY...COUNTRY
ROADS AND FARMLANDS ALONG THE BANKS OF CREEKS...STREAMS AND OTHER LOW
LYING AREAS ARE SUBJECT TO FLOODING.

LAT...LON 3991 7531 3984 7552 3985 7554 3985 7564
      3983 7569 3976 7578 3976 7581 3981 7597
      4021 7568

$$

JJM

The office that day

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

IssuedProductOfficeCountiesLasted
Sep 18, 3:29 AM EDTSevere Thunderstorm WarningPHIChester31 min
Sep 18, 6:09 AM EDTFlash Flood WarningPHICarbon, Lehigh, Monroe, Northampton4 hr
Sep 18, 7:07 AM EDTFlash Flood WarningPHIBucks, Montgomery4 hr
Sep 18, 9:48 AM EDTFlash Flood WarningPHICarbon, Lehigh, Monroe, Northampton4 hr
Sep 18, 10:57 AM EDTFlash Flood WarningPHIBucks, Montgomery3 hr
Sep 18, 1:45 PM EDTFlash Flood WarningPHIBucks, Chester, Delaware, Montgomery2 hr
Sep 18, 2:00 PM EDTFlash Flood WarningPHICarbon, Lehigh, Monroe, Northampton3 hr

Nearby

Flash Flood Warnings in Pennsylvania, 2004Every flash flood warning in 2004

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.