Alert archive / Pennsylvania / Flash Flood Warnings in 1998
Flash Flood Warning 11, NWS Philadelphia/Mount Holly
NWS Philadelphia/Mount Holly issued this flash flood warning at Apr 1, 1998, 9:56 PM EST for Chester County, 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 counties it named.
The facts
- Issued
- Apr 1, 1998, 9:56 PM EST (02:56 UTC)
- Expired
- Apr 2, 1998, 12:00 AM EST
- In force
- 2 hr
- Issued by
- NWS Philadelphia/Mount Holly
- Area
- Whole counties
Counties Chester County, PA, Montgomery County, PA
The radar
The Philadelphia radar (KDIX), 99 km from the middle of the area, began a volume at 02:58 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, 2.9 hours before the alert went out and 203 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.
- Mixed-layer CAPE
- 1170 J/kg
- Mixed-layer CIN
- -6 J/kg
- Mixed-layer LCL
- 817 m above ground
- 0-6 km bulk shear
- 80 kt
- 0-1 km storm-relative helicity
- 104 m²/s²
- 0-3 km storm-relative helicity
- 192 m²/s²
- Significant tornado parameter
- 0.6
- Supercell composite
- 3.7
The text
As transmitted, in the capitals the NWS used until 2016.
000 TTAA00 KPHL 020304 FFWPHL PAC029-091-020500- BULLETIN - EAS ACTIVATION REQUESTED FLASH FLOOD WARNING NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 956 PM EST WED APR 1 1998 THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY HAS EXTENDED THE FLASH FLOOD WARNING EFFECTIVE UNTIL 1200 AM EST TONIGHT FOR PEOPLE IN THE FOLLOWING LOCATIONS... IN PENNSYLVANIA ...ALL OF CHESTER COUNTY ...SOUTHEASTERN AND CENTRAL MONTGOMERY COUNTY NATIONAL WEATHER SERVICE RADAR INDICATED UPWARDS OF 3 INCHES OF RAIN HAD FALLEN ACROSS PARTS OF MONTGOMERY AND CHESTER COUNTY LATE THIS AFTERNOON AND THIS EVENING. MORE RAIN IS EXPECTED OVER THE NEXT HOUR BUT SHOULD TAPER OFF AFTER THAT. THE VALLEY CREEK AT VALLEY FORGE HAS FALLEN TO 6.6 FEET AS OF 955PM WHICH IS BELOW FLOOD STAGE OF 7FT. THE BRANDYWINE CREEK AT DOWNINGTOWN CONTINUES TO RISE AND WAS 8.9 FT AT 955 PM...FLOOD STAGE THERE IS 7 FT. DOWNINGTOWN SHOULD CREST AT BTWEEN 9.5 AND 10 FT OVER THE NEXT COUPLE HOURS. CHADDS FORD...ALSO ON THE BRANDYWINE...HAS RISEN TO 6.02 FT...FLOOD STAGE THERE IS 9 FT. BE ESPECIALLY CAUTIOUS AT NIGHT WHEN IT IS HARDER TO RECOGNIZE THE DANGERS OF FLASH FLOODING. IF FLOODING IS OBSERVED...ACT QUICKLY. MOVE UP TO ESCAPE FLOOD WATERS. DO hNOT STAY IN AREAS SUBJECT TO FLOODING WHEN WATER BEGINS RISING. NPC
The office that day
Everything else NWS Philadelphia/Mount Holly issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 1, 8:10 PM EST | Flash Flood Warning | PHI | Chester, Montgomery | 110 min |
| Apr 1, 9:25 PM EST | Severe Thunderstorm Warning | PHI | Bucks | 50 min |
| Apr 1, 9:43 PM EST | Severe Thunderstorm Warning | PHI | Chester | 32 min |
| Apr 2, 12:30 AM EST | Flash Flood Warning | PHI | Bucks | 3 hr |
Nearby
Flash Flood Warnings in Pennsylvania, 1998Every flash flood warning in 1998
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.