Alert archive / Pennsylvania / Areal Flood Warnings in 2012

Areal Flood Warning 47, NWS Philadelphia/Mount Holly

December 26, 2012Chester County, Pennsylvania

NWS Philadelphia/Mount Holly issued this areal flood warning at Dec 26, 2012, 9:29 PM EST for Chester County, Pennsylvania. It was in force for 118 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued: Dec 26, 2012, 9:29 PM EST (02:29 UTC)
Expired: Dec 26, 2012, 11:27 PM EST
In force: 118 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Flood severity: None

County Chester County, PA

The radar

The Philadelphia radar (KDIX), 95 km from the middle of the area, began a volume at 02:31 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 00:00Z, 2.5 hours before the alert went out and 207 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-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 475 m above ground
0-6 km bulk shear: 74 kt
0-1 km storm-relative helicity: 680 m²/s²
0-3 km storm-relative helicity: 906 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.2

Open this sounding in Storm Lab

The text

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

048 
WGUS41 KPHI 270229
FLWPHI

BULLETIN - IMMEDIATE BROADCAST REQUESTED
FLOOD WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
929 PM EST WED DEC 26 2012

PAC029-270630-
/O.NEW.KPHI.FA.W.0047.121227T0229Z-121227T0630Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
CHESTER PA-
929 PM EST WED DEC 26 2012

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

* FLOOD WARNING FOR URBAN AREAS AND SMALL STREAMS IN...
  EAST CENTRAL CHESTER COUNTY IN SOUTHEAST PENNSYLVANIA...

* UNTIL 130 AM EST

* AT 928 PM EST...RUNOFF FROM THE HEAVY RAIN EARLIER THIS EVENING IS 
PUSHING THE VALLEY CREEK IN VALLEY FORGE TOWARD FLOOD STAGE. THE 
CREEK IS EXPECTED TO CREST ABOVE FLOOD STAGE LATER THIS EVENING... 
AND DROP BELOW FLOOD STAGE EARLY THURSDAY MORNING. 

A FLOOD WARNING MEANS THAT FLOODING IS IMMINENT OR HAS BEEN REPORTED.
STREAM RISES WILL BE SLOW AND FLASH FLOODING IS NOT EXPECTED.
HOWEVER...ALL INTERESTED PARTIES SHOULD TAKE NECESSARY PRECAUTIONS
IMMEDIATELY.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

MOST FLOOD DEATHS OCCUR IN AUTOMOBILES. NEVER DRIVE YOUR VEHICLE INTO
AREAS WHERE THE WATER COVERS THE ROADWAY. FLOOD WATERS ARE USUALLY
DEEPER THAN THEY APPEAR. JUST ONE FOOT OF FLOWING WATER IS POWERFUL
ENOUGH TO SWEEP VEHICLES OFF THE ROAD. WHEN ENCOUNTERING FLOODED
ROADS MAKE THE SMART CHOICE...TURN AROUND...DONT DROWN.

BE ESPECIALLY CAUTIOUS AT NIGHT WHEN IT IS HARDER TO RECOGNIZE THE
DANGERS OF FLOODING. IF 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.

&&

LAT...LON 4018 7554 4016 7552 4015 7553 4016 7551
      4014 7551 4012 7549 4013 7548 4011 7547
      4007 7540 3997 7546 3996 7549 3999 7559
      4012 7563

$$

HAYES

1 follow-up statement

047 
WGUS81 KPHI 270427
FLSPHI

FLOOD STATEMENT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1127 PM EST WED DEC 26 2012

PAC029-270437-
/O.CAN.KPHI.FA.W.0047.000000T0000Z-121227T0630Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
CHESTER PA-
1127 PM EST WED DEC 26 2012

...THE FLOOD WARNING HAS BEEN CANCELLED FOR URBAN AREAS AND SMALL
STREAMS IN EAST CENTRAL CHESTER COUNTY...

FLOODING IS NO LONGER EXPECTED ON THE VALLEY CREEK.

LAT...LON 4018 7554 4016 7552 4015 7553 4016 7551
      4014 7551 4012 7549 4013 7548 4011 7547
      4007 7540 3997 7546 3996 7549 3999 7559
      4012 7563

$$

HAYES

The office that day

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

Issued	Product	Office	Counties	Lasted
Dec 26, 7:55 PM EST	Areal Flood Advisory	PHI	Bucks, Chester, Delaware, Montgomery, Philadelphia	6 hr
Dec 26, 9:10 PM EST	Areal Flood Advisory	PHI	Bucks, Lehigh, Northampton	4 hr

Nearby

Areal Flood Warnings in Pennsylvania, 2012 Every areal flood warning in 2012

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.