Alert archive / Pennsylvania / Flash Flood Warnings in 2009

Flash Flood Warning 43, NWS Philadelphia/Mount Holly

August 12, 2009Berks County, Lehigh County, Northampton County, Pennsylvania

NWS Philadelphia/Mount Holly issued this flash flood warning at Aug 12, 2009, 11:23 PM EDT for Berks County, Lehigh County, Northampton County, Pennsylvania. It was in force for 7 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 12, 2009, 11:23 PM EDT (03:23 UTC)
Expired
Aug 13, 2009, 6:12 AM EDT
In force
7 hr
Issued by
NWS Philadelphia/Mount Holly
Area
Storm-based polygon
Flood severity
None

Counties Berks County, PA, Lehigh County, PA, Northampton County, PA

The radar

The Philadelphia radar (KDIX), 125 km from the middle of the area, began a volume at 03:26 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

Brookhaven, NY (KOKX), launched 00:00Z, 3.4 hours before the alert went out and 223 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, Brookhaven, NY at 00:00Z on 2009-08-13Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 136 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, Brookhaven, NY at 00:00Z on 2009-08-13The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 10 square meters per square second.19395878Sfc1 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
136 J/kg
Mixed-layer CIN
-72 J/kg
Mixed-layer LCL
544 m above ground
0-6 km bulk shear
30 kt
0-1 km storm-relative helicity
10 m²/s²
0-3 km storm-relative helicity
70 m²/s²
Significant tornado parameter
0.0
Supercell composite
1.4

Open this sounding in Storm Lab

The text

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

000 
WGUS51 KPHI 130323
FFWPHI
PAC011-077-095-130715-
/O.NEW.KPHI.FF.W.0043.090813T0323Z-090813T0715Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1123 PM EDT WED AUG 12 2009

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

* FLASH FLOOD WARNING FOR...
  NORTHEASTERN BERKS COUNTY IN EASTERN PENNSYLVANIA...
  LEHIGH COUNTY IN EASTERN PENNSYLVANIA...
  THIS INCLUDES THE CITY OF ALLENTOWN...
  WESTERN NORTHAMPTON COUNTY IN EASTERN PENNSYLVANIA...

* UNTIL 315 AM EDT

* AT 1118 PM EDT...NATIONAL WEATHER SERVICE RADAR INDICATED FLASH
  FLOODING FROM CONTINUING THUNDERSTORMS OVER THE WARNED AREA. RADAR
  ESTIMATED BETWEEN 2 AND 3 INCHES OF RAIN HAD FALLEN DURING THE
  PAST HOUR.

* LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO
  BEERSVILLE...WIND GAP...NORTHAMPTON...NAZARETH AND BATH

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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.

BE ESPECIALLY CAUTIOUS AT NIGHT WHEN IT IS HARDER TO RECOGNIZE THE
DANGERS OF FLOODING. IF FLASH FLOODING IS OBSERVED ACT QUICKLY. MOVE
UP TO HIGHER GROUND TO ESCAPE FLOOD WATERS. DO NOT STAY IN AREAS
SUBJECT TO FLOODING WHEN WATER BEGINS RISING.

IN HILLY TERRAIN THERE ARE HUNDREDS OF LOW WATER CROSSINGS WHICH ARE
POTENTIALLY DANGEROUS IN HEAVY RAIN. DO NOT ATTEMPT TO TRAVEL ACROSS
FLOODED ROADS. FIND ALTERNATE ROUTES. IT TAKES ONLY A FEW INCHES OF
SWIFTLY FLOWING WATER TO CARRY VEHICLES AWAY.

&&

LAT...LON 4068 7551 4079 7558 4084 7535 4088 7522
      4064 7535 4038 7565 4064 7590

$$
2 follow-up statements
000 
WGUS51 KPHI 130705
FFWPHI
PAC011-077-095-131115-
/O.EXT.KPHI.FF.W.0043.000000T0000Z-090813T1115Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
305 AM EDT THU AUG 13 2009

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS EXTENDED THE

* FLASH FLOOD WARNING FOR...
  NORTHEASTERN BERKS COUNTY IN EASTERN PENNSYLVANIA...
  LEHIGH COUNTY IN EASTERN PENNSYLVANIA...
  THIS INCLUDES THE CITY OF ALLENTOWN...
  WESTERN NORTHAMPTON COUNTY IN EASTERN PENNSYLVANIA...

* UNTIL 715 AM EDT

* AT 304 AM EDT...RAINS AND AREAS OF FLOODING CONTINUE ACROSS THE    
  WARNED AREA.  

* LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO
  BEERSVILLE...WIND GAP...NAZARETH AND BATH

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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.

BE ESPECIALLY CAUTIOUS AT NIGHT WHEN IT IS HARDER TO RECOGNIZE THE
DANGERS OF FLOODING. IF FLASH FLOODING IS OBSERVED ACT QUICKLY. MOVE
UP TO HIGHER GROUND TO ESCAPE FLOOD WATERS. DO NOT STAY IN AREAS
SUBJECT TO FLOODING WHEN WATER BEGINS RISING.

IN HILLY TERRAIN THERE ARE HUNDREDS OF LOW WATER CROSSINGS WHICH ARE
POTENTIALLY DANGEROUS IN HEAVY RAIN. DO NOT ATTEMPT TO TRAVEL ACROSS
FLOODED ROADS. FIND ALTERNATE ROUTES. IT TAKES ONLY A FEW INCHES OF
SWIFTLY FLOWING WATER TO CARRY VEHICLES AWAY.

&&

LAT...LON 4068 7551 4079 7558 4084 7535 4088 7522
      4064 7535 4038 7565 4064 7590

$$

PO
000 
WGUS71 KPHI 131012
FFSPHI

FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
612 AM EDT THU AUG 13 2009

PAC011-077-095-131022-
/O.CAN.KPHI.FF.W.0043.000000T0000Z-090813T1115Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
BERKS PA-LEHIGH PA-NORTHAMPTON PA-
612 AM EDT THU AUG 13 2009

...THE FLASH FLOOD WARNING HAS BEEN CANCELLED FOR WESTERN
NORTHAMPTON...LEHIGH AND NORTHEASTERN BERKS COUNTIES...

THE THREAT OF HEAVY RAINS HAS PASSED. AREAS STREAMS AND CREEKS MAY 
CONTINUE TO RUN HIGH THROUGH THE MORNING. 

LAT...LON 4068 7551 4079 7558 4084 7535 4088 7522
      4064 7535 4038 7565 4064 7590

$$

PO

The office that day

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

IssuedProductOfficeCountiesLasted
Aug 12, 8:54 PM EDTFlash Flood WarningPHICarbon4 hr
Aug 12, 10:33 PM EDTFlash Flood WarningPHICarbon, Lehigh, Northampton4 hr
Aug 12, 10:42 PM EDTFlash Flood WarningPHIBerks4 hr
Aug 13, 2:58 AM EDTAreal Flood AdvisoryPHIChester3 hr
Aug 13, 3:36 AM EDTFlood WatchPHIBerks, Carbon, Delaware, Lehigh, Monroe, Northampton and 1 more36 min
Aug 13, 4:12 AM EDTFlash Flood WatchPHIBerks, Carbon, Delaware, Lehigh, Monroe, Northampton and 1 more15 hr
Aug 13, 6:01 AM EDTRiver Flood WarningPHIChester5 hr
Aug 13, 9:13 AM EDTRiver Flood WarningPHIChester, Delaware5 hr

Nearby

Flash Flood Warnings in Pennsylvania, 2009Every flash flood warning in 2009

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.