Alert archive / Pennsylvania / Areal Flood Warnings in 2020

Areal Flood Warning 49, NWS Philadelphia/Mount Holly

November 30, 20204 counties in Pennsylvania

NWS Philadelphia/Mount Holly issued this areal flood warning at Nov 30, 2020, 2:17 PM EST for 4 counties in Pennsylvania. It was in force for 9 hr. 7 reports came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued
Nov 30, 2020, 2:17 PM EST (19:17 UTC)
Expired
Nov 30, 2020, 11:01 PM EST
In force
9 hr
Issued by
NWS Philadelphia/Mount Holly
Area
Storm-based polygon
Flood severity
None

Counties Berks County, PA, Bucks County, PA, Lehigh County, PA, Montgomery County, PA

The radar

The Philadelphia radar (KDIX), 105 km from the middle of the area, began a volume at 19:17 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.

What was reported inside it

TimeReportWhereRemark
Nov 30, 4:06 PM ESTFLOOD1 Wsw Sanatoga, PAWATER RESCUE ON ARMAND HAMMER BOULEVARD AND SUNSET DRIVE. TIME BASED ON DISPATCH REPORT.
Nov 30, 4:15 PM ESTFLOOD2 Sw Pennsburg, PATHE WEST BRANCH PERKIOMEN CREEK AT HILLEGASS (HLGP1) REACHED FLOOD STAGE AT 415 PM AND CRESTED AT 5.27 FEET AT 545 PM.
Nov 30, 5:30 PM ESTFLOOD2 Ene Schwenksville, PACORRECTS PREVIOUS FLOOD REPORT FROM 2 ENE SCHWENKSVILLE. THE EAST BRANCH PERKIOMEN CREEK AT SCHWENKSVILLE (SWVP1) REACHED FLOOD STAGE AT 530 PM AND CRESTED AT 8.31 FEET AT 615 PM.
Nov 30, 5:30 PM ESTFLOOD2 Ene Schwenksville, PATHE EAST BRANCH PERKIOMEN CREEK AT SCHWENKSVILLE (SWVP1) REACHED FLOOD STAGE AT 530 PM AND CRESTED AT 8.31 FEET AT 715 PM.
Nov 30, 5:30 PM ESTFLOODGraterford, PATHE PERKIOMEN CREEK AT GRATERFORD (GRAP1) REACHED FLOOD STAGE AT 530 PM AND CRESTED AT 12.46 FEET AT 900 PM.
Nov 30, 7:30 PM ESTFLOOD1 N Schwenksville, PAWATER RESCUE ON PARK AVENUE. TIME BASED ON DISPATCH REPORT.
Nov 30, 8:33 PM ESTFLOOD2 Wnw Salford Twp, PASWAMP CREEK ROAD BETWEEN WHITES MILL ROAD AND MILLER ROAD CLOSED FROM FLOODING. TIME BASED ON DISPATCH REPORT.

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 7.3 hours before the alert went out and 218 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 2020-11-30Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 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 12:00Z on 2020-11-30The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 384 square meters per square second.1939587897117Sfc1 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
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
498 m above ground
0-6 km bulk shear
56 kt
0-1 km storm-relative helicity
384 m²/s²
0-3 km storm-relative helicity
623 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

158 
WGUS41 KPHI 301917
FLWPHI

BULLETIN - EAS ACTIVATION REQUESTED
Flood Warning
National Weather Service Mount Holly NJ
217 PM EST Mon Nov 30 2020

PAC011-017-077-091-302215-
/O.NEW.KPHI.FA.W.0049.201130T1917Z-201130T2215Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Berks PA-Bucks PA-Lehigh PA-Montgomery PA-
217 PM EST Mon Nov 30 2020

The National Weather Service in Mount Holly has issued a

* Flood Warning for...
  East Central Berks County in eastern Pennsylvania...
  Southeastern Lehigh County in eastern Pennsylvania...
  West Central Bucks County in southeastern Pennsylvania...
  Northwestern Montgomery County in southeastern Pennsylvania...

* Until 515 PM EST.

* At 217 PM EST, Doppler radar indicated heavy rain due to 
  thunderstorms. Flooding is ongoing or expected to begin shortly in 
  the warned area.

Some locations that may experience flooding include...
  Pottstown, Emmaus, Quakertown, Perkasie, Souderton, Collegeville, 
  Royersford, Trappe, Hatfield, East Greenville, Schwenksville, and 
  Bally.

This includes the following highways...
	Northeast Extension between exits 31 and 51.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around...don't drown when encountering flooded roads. Most 
flood deaths occur in vehicles.

&&

LAT...LON 4043 7568 4050 7560 4054 7545 4035 7519
      4017 7548 4020 7555 4021 7556 4020 7556
      4021 7559 4024 7560 4022 7561 4024 7565

$$

PO
4 follow-up statements
383 
WGUS41 KPHI 302153
FLWPHI

BULLETIN - EAS ACTIVATION REQUESTED
Flood Warning
National Weather Service Mount Holly NJ
453 PM EST Mon Nov 30 2020

PAC011-017-077-091-010115-
/O.EXT.KPHI.FA.W.0049.000000T0000Z-201201T0115Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Berks PA-Bucks PA-Lehigh PA-Montgomery PA-
453 PM EST Mon Nov 30 2020

The National Weather Service in Mount Holly has extended the

* Flood Warning for...
  East Central Berks County in eastern Pennsylvania...
  Southeastern Lehigh County in eastern Pennsylvania...
  West Central Bucks County in southeastern Pennsylvania...
  Northwestern Montgomery County in southeastern Pennsylvania...

* Until 815 PM EST.

* At 453 PM EST, Doppler radar indicated a continuation of rains 
  across areas that have already received heavy rains earlier today.

Some locations that may experience flooding include...
  Pottstown, Emmaus, Quakertown, Perkasie, Souderton, Collegeville, 
  Royersford, Trappe, Hatfield, East Greenville, Schwenksville, and 
  Bally.

This includes the following highways...
	Northeast Extension between exits 31 and 51.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around...don't drown when encountering flooded roads. Most 
flood deaths occur in vehicles.

&&

LAT...LON 4043 7568 4050 7560 4054 7545 4035 7519
      4017 7548 4020 7555 4021 7556 4020 7556
      4021 7559 4024 7560 4022 7561 4024 7565

$$

PO
214 
WGUS41 KPHI 010108 RRA
FLWPHI

BULLETIN - EAS ACTIVATION REQUESTED
Flood Warning
National Weather Service Mount Holly NJ
808 PM EST Mon Nov 30 2020

PAC011-017-077-091-010315-
/O.EXT.KPHI.FA.W.0049.000000T0000Z-201201T0315Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Berks PA-Bucks PA-Lehigh PA-Montgomery PA-
808 PM EST Mon Nov 30 2020

The National Weather Service in Mount Holly has extended the

* Flood Warning for...
  East Central Berks County in eastern Pennsylvania...
  Southeastern Lehigh County in eastern Pennsylvania...
  West Central Bucks County in southeastern Pennsylvania...
  Northwestern Montgomery County in southeastern Pennsylvania...

* Until 1015 PM EST.

* At 808 PM EST, Doppler radar and automated rain gauges indicated 
  heavy rain due to thunderstorms. Flooding is already occurring in 
  the warned area.

For Perkiomen Creek at East Greenville:
At 7:47pm the stage was 6.07 feet.
Flood Stage is 4 feet.
...
For Perkiomen Creek at Graterford:
At 8:02pm the stage was 12.33 feet.
Flood Stage is 11 feet.
...
For West Branch Perkiomen Creek at Hillegass:
At 7:15pm the stage was 5.01 feet.
Flood Stage is 5 feet.
...
For East Branch Perkiomen at Schwenksville:
At 7:15pm the stage was 8.04 feet.
Flood Stage is 8 feet.

This includes the following highways...
	Northeast Extension between exits 31 and 51.

Flooding is occurring along the Perkiomen Creek at East Greenville 
and at Graterford, and the East Branch of the Perkiomen at 
Schwenksville.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around...don't drown when encountering flooded roads. Most 
flood deaths occur in vehicles.

&&

LAT...LON 4043 7568 4050 7560 4054 7545 4035 7519
      4017 7548 4020 7555 4021 7556 4020 7556
      4021 7559 4024 7560 4022 7561 4024 7565

$$

JEO
232 
WGUS41 KPHI 010302
FLWPHI

BULLETIN - EAS ACTIVATION REQUESTED
Flood Warning
National Weather Service Mount Holly NJ
1002 PM EST Mon Nov 30 2020

PAC011-017-077-091-010700-
/O.EXT.KPHI.FA.W.0049.000000T0000Z-201201T0700Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Berks PA-Bucks PA-Lehigh PA-Montgomery PA-
1002 PM EST Mon Nov 30 2020

The National Weather Service in Mount Holly has extended the

* Flood Warning for...
  East Central Berks County in eastern Pennsylvania...
  Southeastern Lehigh County in eastern Pennsylvania...
  West Central Bucks County in southeastern Pennsylvania...
  Northwestern Montgomery County in southeastern Pennsylvania...

* Until 200 AM EST.

* At 1002 PM EST, minor flooding was continuing on many streams and 
  creeks.

Water levels will decrease slowly overnight with most streams and 
creeks returning within their banks on Tuesday morning.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around, don't drown when encountering flooded roads. Most flood 
deaths occur in vehicles.

&&

LAT...LON 4043 7568 4050 7560 4054 7545 4035 7519
      4017 7548 4020 7555 4021 7556 4020 7556
      4021 7559 4024 7560 4022 7561 4024 7565

$$

Iovino
364 
WGUS81 KPHI 010401
FLSPHI

Flood Statement
National Weather Service Mount Holly NJ
1101 PM EST Mon Nov 30 2020

PAC011-017-077-091-010411-
/O.CAN.KPHI.FA.W.0049.000000T0000Z-201201T0700Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Berks PA-Bucks PA-Lehigh PA-Montgomery PA-
1101 PM EST Mon Nov 30 2020

...FLOOD WARNING IS CANCELLED FOR EAST CENTRAL BERKS, SOUTHEASTERN 
LEHIGH, WEST CENTRAL BUCKS, AND NORTHWESTERN MONTGOMERY COUNTIES...

Minor flooding will linger on the lower Perkiomen Creek in 
Montgomery County. Otherwise, flooding is no longer expected to pose 
a threat. Please continue to heed remaining road closures.

LAT...LON 4043 7568 4050 7560 4054 7545 4035 7519
      4017 7548 4020 7555 4021 7556 4020 7556
      4021 7559 4024 7560 4022 7561 4024 7565

$$

Iovino

The office that day

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

IssuedProductOfficeCountiesLasted
Nov 30, 12:15 PM ESTAreal Flood AdvisoryPHIChester, Delaware3 hr
Nov 30, 12:41 PM ESTSpecial Weather StatementPHIChester, Montgomery49 min
Nov 30, 2:18 PM ESTCoastal Flood AdvisoryPHIBucks, Delaware, Philadelphia2 hr
Nov 30, 2:41 PM ESTSevere Thunderstorm WarningPHIChester, Delaware49 min
Nov 30, 2:48 PM ESTAreal Flood WarningPHIChester, Delaware, Montgomery8 hr
Nov 30, 3:01 PM ESTSevere Thunderstorm WarningPHIChester, Delaware, Montgomery, Philadelphia44 min
Nov 30, 3:26 PM ESTAreal Flood WarningPHIBerks, Bucks, Carbon, Lehigh, Monroe, Northampton4 hr
Nov 30, 3:43 PM ESTSevere Thunderstorm WarningPHIBerks, Bucks, Lehigh, Monroe, Montgomery, Northampton and 1 more47 min
Nov 30, 3:51 PM ESTRiver Flood WarningPHIChester14 hr
Nov 30, 3:53 PM ESTAreal Flood WarningPHIMonroe, Northampton16 hr
Nov 30, 3:53 PM ESTTornado WarningPHIBucks, Montgomery13 min
Nov 30, 4:17 PM ESTAreal Flood WarningPHIBucks, Delaware, Montgomery, Philadelphia10 hr
Nov 30, 5:30 PM ESTRiver Flood WarningPHIChester, Delaware16 hr
Nov 30, 5:33 PM ESTRiver Flood WarningPHIMontgomery10 hr
Nov 30, 5:35 PM ESTRiver Flood WarningPHIDelaware4 hr

Nearby

Areal Flood Warnings in Pennsylvania, 2020Every areal flood warning in 2020

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.