Alert archive / Pennsylvania / Flash Flood Warnings in 2004

Flash Flood Warning 49, NWS Philadelphia/Mount Holly

August 1, 2004Montgomery County, Pennsylvania

NWS Philadelphia/Mount Holly issued this flash flood warning at Aug 1, 2004, 7:12 AM EDT for Montgomery County, Pennsylvania. It was in force for 2 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
Aug 1, 2004, 7:12 AM EDT (11:12 UTC)
Expired
Aug 1, 2004, 9:15 AM EDT
In force
2 hr
Issued by
NWS Philadelphia/Mount Holly
Area
Counties, with a storm outline in the text

County Montgomery County, PA

The radar

The Philadelphia radar (KDIX), 77 km from the middle of the area, began a volume at 11:13 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, 11.2 hours before the alert went out and 219 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 2004-08-01Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 989 joules per kilogram.LCLEL10008507005003002001001 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 2004-08-01The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 51 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
989 J/kg
Mixed-layer CIN
-8 J/kg
Mixed-layer LCL
1351 m above ground
0-6 km bulk shear
21 kt
0-1 km storm-relative helicity
51 m²/s²
0-3 km storm-relative helicity
79 m²/s²
Significant tornado parameter
0.0
Supercell composite
1.0

Open this sounding in Storm Lab

The text

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

000 
WGUS51 KPHI 011112
FFWPHI
PAC091-011315-

BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
712 AM EDT SUN AUG 1 2004

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

* FLASH FLOOD WARNING FOR...
  SOUTH CENTRAL MONTGOMERY COUNTY IN SOUTHEAST PENNSYLVANIA

* UNTIL 915 AM EDT

* AT 709 AM EDT...FLASH FLOODING WAS INDICATED BY NATIONAL WEATHER
  SERVICE RADAR ALONG COBBS CREEK IN SOUTHERN MONTGOMERY COUNTY
  NEAR THE CITY OF PHILADELPHIA.

EXCESSIVE RUNOFF FROM HEAVY RAINFALL WILL CAUSE FLOODING OF SMALL 
CREEKS AND STREAMS...URBAN AREAS...HIGHWAYS...STREETS AND UNDERPASSES
AS WELL AS OTHER DRAINAGE AREAS AND LOW LYING SPOTS.

LAT...LON 4007 7538 4000 7529 4002 7524 4006 7527
      4010 7523 4016 7529

$$
MPD

The office that day

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

IssuedProductOfficeCountiesLasted
Aug 1, 7:30 AM EDTFlash Flood WarningPHIPhiladelphia2 hr
Aug 1, 7:43 AM EDTFlash Flood WarningPHIBucks2 hr
Aug 1, 7:50 AM EDTFlash Flood WarningPHIChester, Delaware115 min
Aug 1, 8:01 AM EDTFlash Flood WarningPHIMontgomery89 min
Aug 1, 9:08 AM EDTFlash Flood WarningPHIChester, Delaware, Montgomery, Philadelphia2 hr
Aug 1, 10:59 AM EDTFlash Flood WarningPHIDelaware, Montgomery, Philadelphia2 hr
Aug 1, 12:52 PM EDTFlash Flood WarningPHIDelaware, Philadelphia4 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.