Alert archive / Pennsylvania / Areal Flood Advisories in 2021

Areal Flood Advisory 5, NWS Philadelphia/Mount Holly

March 24, 20214 counties in Pennsylvania; 4 counties in New Jersey

NWS Philadelphia/Mount Holly issued this areal flood advisory at Mar 24, 2021, 2:45 PM EDT for 4 counties in Pennsylvania; 4 counties in New Jersey. It was in force for 5 hr.

The area

The outline as issued.

The facts

Issued: Mar 24, 2021, 2:45 PM EDT (18:45 UTC)
Expired: Mar 24, 2021, 7:45 PM EDT
In force: 5 hr
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon

Counties Hunterdon County, NJ, Mercer County, NJ, Middlesex County, NJ, Somerset County, NJ, Berks County, PA, Bucks County, PA, Chester County, PA, Montgomery County, PA

The radar

The Philadelphia radar (KDIX), 70 km from the middle of the area, began a volume at 18:46 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 12:00Z, 6.8 hours before the alert went out and 200 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: 1342 m above ground
0-6 km bulk shear: 32 kt
0-1 km storm-relative helicity: 82 m²/s²
0-3 km storm-relative helicity: 135 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

916 
WGUS81 KPHI 241845
FLSPHI

Flood Advisory
National Weather Service Mount Holly NJ
245 PM EDT Wed Mar 24 2021

NJC019-021-023-035-PAC011-017-029-091-242145-
/O.NEW.KPHI.FA.Y.0005.210324T1845Z-210324T2145Z/
/00000.N.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Hunterdon NJ-Mercer NJ-Middlesex NJ-Somerset NJ-Berks PA-Bucks PA-
Chester PA-Montgomery PA-
245 PM EDT Wed Mar 24 2021

The National Weather Service in Mount Holly has issued a

* Flood Advisory for...
  Mercer County in central New Jersey...
  Southwestern Middlesex County in northern New Jersey...
  Southwestern Somerset County in northern New Jersey...
  Southern Hunterdon County in northwestern New Jersey...
  Southeastern Berks County in eastern Pennsylvania...
  Bucks County in southeastern Pennsylvania...
  Northeastern Chester County in southeastern Pennsylvania...
  Montgomery County in southeastern Pennsylvania...

* Until 545 PM EDT.

* At 245 PM EDT, Doppler radar indicated heavy rain. Minor flooding 
  is ongoing or expected to begin shortly in the advisory area. Up 
  to 0.5 inches of rain have fallen.

Some locations that may experience flooding include...
  Philadelphia, Trenton, East Brunswick, South Brunswick, Ewing, 
  Norristown, Pottstown, Phoenixville, Lansdale, West Norriton, East 
  Norriton, and Princeton.

This includes the following highways...
	New Jersey Turnpike between exits 8A and 9.
	Pennsylvania Turnpike between exits 340 and 351...and
	between exits 355 and 356.
	Interstate 295 in New Jersey between mile markers 59 and 76.
	Interstate 195 in New Jersey between mile markers 0 and 5.
	Interstate 176 in Pennsylvania between mile markers 4 and 8.
	Northeast Extension between exits 22 and 44.

Additional rainfall of 0.5 to 1 inch is expected over the area. This 
additional rain will result in minor flooding.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Flood Advisory means river or stream flows are elevated, or 
ponding of water in urban or other areas is occurring or is imminent.

&&

LAT...LON 4024 7600 4040 7548 4063 7506 4047 7452
      4031 7438 4018 7468 4018 7470 4015 7470
      4011 7480 4015 7584

$$

SFJ

3 follow-up statements

295 
WGUS81 KPHI 242034
FLSPHI

Flood Advisory
National Weather Service Mount Holly NJ
434 PM EDT Wed Mar 24 2021

NJC019-021-023-035-PAC011-017-029-091-242145-
/O.CON.KPHI.FA.Y.0005.000000T0000Z-210324T2145Z/
/00000.N.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Hunterdon NJ-Mercer NJ-Middlesex NJ-Somerset NJ-Berks PA-Bucks PA-
Chester PA-Montgomery PA-
434 PM EDT Wed Mar 24 2021

...FLOOD ADVISORY REMAINS IN EFFECT UNTIL 545 PM EDT THIS AFTERNOON 
FOR MERCER, SOUTHWESTERN MIDDLESEX, SOUTHWESTERN SOMERSET, SOUTHERN 
HUNTERDON, SOUTHEASTERN BERKS, BUCKS, NORTHEASTERN CHESTER, AND 
MONTGOMERY COUNTIES...

At 434 PM EDT, Doppler radar indicated heavy rain. Minor flooding is 
ongoing or expected to begin shortly in the advisory area. Between 
0.5 and 1 inch of rain has fallen.

Some locations that may experience flooding include...
Trenton, East Brunswick, South Brunswick, Ewing, Norristown, 
Pottstown, Phoenixville, Lansdale, West Norriton, East Norriton, and 
Princeton.

This includes the following highways...
	New Jersey Turnpike between exits 8A and 9.
	Pennsylvania Turnpike between exits 340 and 358.
	Interstate 295 in New Jersey between mile markers 59 and 76.
	Interstate 195 in New Jersey between mile markers 0 and 5.
	Interstate 176 in Pennsylvania between mile markers 4 and 8.
	Northeast Extension between exits 22 and 43.

Additional rainfall of 0.5 to 1 inch is expected over the area. This 
additional rain will result in minor flooding.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Flood Advisory means river or stream flows are elevated, or 
ponding of water in urban or other areas is occurring or is imminent.

&&

LAT...LON 4024 7600 4040 7548 4063 7506 4047 7452
      4031 7438 4018 7468 4018 7470 4015 7470
      4011 7480 4015 7584

$$

SFJ

971 
WGUS81 KPHI 242105
FLSPHI

Flood Advisory
National Weather Service Mount Holly NJ
505 PM EDT Wed Mar 24 2021

NJC019-021-023-035-PAC011-017-029-091-242345-
/O.EXT.KPHI.FA.Y.0005.000000T0000Z-210324T2345Z/
/00000.N.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Hunterdon NJ-Mercer NJ-Middlesex NJ-Somerset NJ-Berks PA-Bucks PA-
Chester PA-Montgomery PA-
505 PM EDT Wed Mar 24 2021

The National Weather Service in Mount Holly has extended the

* Flood Advisory for...
  Mercer County in central New Jersey...
  Southwestern Middlesex County in northern New Jersey...
  Southwestern Somerset County in northern New Jersey...
  Southern Hunterdon County in northwestern New Jersey...
  Southeastern Berks County in eastern Pennsylvania...
  Bucks County in southeastern Pennsylvania...
  Northeastern Chester County in southeastern Pennsylvania...
  Montgomery County in southeastern Pennsylvania...

* Until 745 PM EDT.

* At 505 PM EDT, Doppler radar indicated heavy rain. Minor flooding 
  is ongoing or expected to begin shortly in the advisory area. 
  Between 1 and 1.5 inches of rain have fallen.

Some locations that may experience flooding include...
  Trenton, East Brunswick, South Brunswick, Ewing, Norristown, 
  Pottstown, Phoenixville, Lansdale, West Norriton, East Norriton, 
  and Princeton.

This includes the following highways...
	New Jersey Turnpike between exits 8A and 9.
	Pennsylvania Turnpike between exits 340 and 358.
	Interstate 295 in New Jersey between mile markers 59 and 76.
	Interstate 195 in New Jersey between mile markers 0 and 5.
	Interstate 176 in Pennsylvania between mile markers 4 and 8.
	Northeast Extension between exits 22 and 43.

Additional rainfall of 0.5 to 1 inch is expected over the area. This 
additional rain will result in minor flooding.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Flood Advisory means river or stream flows are elevated, or 
ponding of water in urban or other areas is occurring or is imminent.

&&

LAT...LON 4024 7600 4040 7548 4063 7506 4047 7452
      4031 7438 4018 7468 4018 7470 4015 7470
      4011 7480 4015 7584

$$

SFJ

484 
WGUS81 KPHI 242348
FLSPHI

Flood Advisory
National Weather Service Mount Holly NJ
748 PM EDT Wed Mar 24 2021

NJC019-021-023-035-PAC011-017-029-091-242358-
/O.EXP.KPHI.FA.Y.0005.000000T0000Z-210324T2345Z/
/00000.N.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Hunterdon NJ-Mercer NJ-Middlesex NJ-Somerset NJ-Berks PA-Bucks PA-
Chester PA-Montgomery PA-
748 PM EDT Wed Mar 24 2021

...FLOOD ADVISORY HAS EXPIRED FOR MERCER, SOUTHWESTERN MIDDLESEX, 
SOUTHWESTERN SOMERSET, SOUTHERN HUNTERDON, SOUTHEASTERN BERKS, 
BUCKS, NORTHEASTERN CHESTER, AND MONTGOMERY COUNTIES...

The heavy rain has ended. Flooding is no longer expected to pose a 
widespread threat. Please continue to heed remaining road closures.

LAT...LON 4024 7600 4040 7548 4063 7506 4047 7452
      4031 7438 4018 7468 4018 7470 4015 7470
      4011 7480 4015 7584

$$

SFJ

The office that day

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

Issued	Product	Office	Counties	Lasted
Mar 24, 1:51 PM EDT	Areal Flood Advisory	PHI	Bucks, Chester, Delaware, Montgomery, Philadelphia	5 hr
Mar 24, 6:26 PM EDT	Areal Flood Warning	PHI	Montgomery, Philadelphia	10 hr
Mar 24, 7:09 PM EDT	Dense Fog Advisory	PHI	Berks, Bucks, Carbon, Chester, Delaware, Lehigh and 4 more	14 hr
Mar 24, 3:02 PM EDT	Marine Dense Fog Advisory	PHI		21 hr
Mar 24, 5:08 PM EDT	Areal Flood Advisory	PHI	Burlington, Camden, Monmouth, Ocean	3 hr

Nearby

Areal Flood Advisories in Pennsylvania, 2021 Areal Flood Advisories in New Jersey, 2021 Every areal flood advisory in 2021

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.