Alert archive / Pennsylvania / Areal Flood Advisories in 2021

Areal Flood Advisory 41, NWS Philadelphia/Mount Holly

July 1, 20214 counties in Pennsylvania; New Castle County, Delaware

NWS Philadelphia/Mount Holly issued this areal flood advisory at Jul 1, 2021, 3:48 PM EDT for 4 counties in Pennsylvania; New Castle County, Delaware. It was in force for 112 min.

The area

The outline as issued.

The facts

Issued: Jul 1, 2021, 3:48 PM EDT (19:48 UTC)
Expired: Jul 1, 2021, 5:40 PM EDT
In force: 112 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon

Counties New Castle County, DE, Bucks County, PA, Delaware County, PA, Montgomery County, PA, Philadelphia County, PA

The radar

The Philadelphia radar (KDIX), 88 km from the middle of the area, began a volume at 19:49 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 12:00Z, 7.8 hours before the alert went out and 194 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: 604 J/kg
Mixed-layer CIN: -48 J/kg
Mixed-layer LCL: 928 m above ground
0-6 km bulk shear: 32 kt
0-1 km storm-relative helicity: 61 m²/s²
0-3 km storm-relative helicity: 108 m²/s²
Significant tornado parameter: 0.2
Supercell composite: 1.2

Open this sounding in Storm Lab

The text

As transmitted.

969 
WGUS81 KPHI 011948
FLSPHI

Flood Advisory
National Weather Service Mount Holly NJ
348 PM EDT Thu Jul 1 2021

DEC003-PAC017-045-091-101-012230-
/O.NEW.KPHI.FA.Y.0041.210701T1948Z-210701T2230Z/
/00000.N.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
New Castle DE-Bucks PA-Delaware PA-Montgomery PA-Philadelphia PA-
348 PM EDT Thu Jul 1 2021

The National Weather Service in Mount Holly has issued a

* Flood Advisory for...
  New Castle County in northern Delaware...
  Southeastern Bucks County in southeastern Pennsylvania...
  Delaware County in southeastern Pennsylvania...
  Southeastern Montgomery County in southeastern Pennsylvania...
  Philadelphia County in southeastern Pennsylvania...

* Until 630 PM EDT.

* At 348 PM EDT, Doppler radar indicated that heavy rain due to 
  thunderstorms was approaching from the west. Minor flooding is 
  expected to begin shortly in the advisory area. Rainfall amounts 
  of 1 to 2 inches are possible in a short amount of time.

* Some locations that may experience flooding include...
  Philadelphia, Wilmington, Newark, Bensalem, Norristown, Chester, 
  West Norriton and East Norriton.

This includes the following highways...
	Pennsylvania Turnpike between mile markers 329 and 359.
	Interstate 95 in Pennsylvania between mile markers 0 and 40.
	Interstate 95 in Delaware between mile markers 0 and 23.
	Interstate 76 in Pennsylvania between mile markers 329 and 351.
	Interstate 676 in Pennsylvania between mile markers 0 and 1.
	Interstate 476 in Pennsylvania between mile markers 0 and 19.
	Northeast Extension between mile markers 21 and 22.

This includes the following DSS Events...
	Welcome America Events.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Be aware of your surroundings and do not drive on flooded roads.

&&

LAT...LON 3950 7578 3972 7579 3984 7560 4007 7536
      4007 7540 4040 7497 4016 7472 3996 7513
      3988 7515 3980 7542 3980 7541 3963 7556
      3957 7550 3965 7548 3962 7541 3961 7541
      3961 7545 3950 7556

$$

Iovino

1 follow-up statement

519 
WGUS81 KPHI 012140
FLSPHI

Flood Advisory
National Weather Service Mount Holly NJ
540 PM EDT Thu Jul 1 2021

DEC003-PAC017-045-091-101-012150-
/O.CAN.KPHI.FA.Y.0041.000000T0000Z-210701T2230Z/
/00000.N.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
New Castle DE-Bucks PA-Delaware PA-Montgomery PA-Philadelphia PA-
540 PM EDT Thu Jul 1 2021

...FLOOD ADVISORY IS CANCELLED FOR NEW CASTLE, SOUTHEASTERN BUCKS, 
DELAWARE, SOUTHEASTERN MONTGOMERY, AND PHILADELPHIA COUNTIES...

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

LAT...LON 3950 7578 3972 7579 3984 7560 4007 7536
      4007 7540 4040 7497 4016 7472 3996 7513
      3988 7515 3980 7542 3980 7541 3963 7556
      3957 7550 3965 7548 3962 7541 3961 7541
      3961 7545 3950 7556

$$

Iovino

The office that day

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

Issued	Product	Office	Counties	Lasted
Jun 30, 8:16 PM EDT	Special Weather Statement	PHI	Bucks, Montgomery	44 min
Jun 30, 8:37 PM EDT	Severe Thunderstorm Warning	PHI	Bucks	38 min
Jul 1, 2:51 PM EDT	Special Weather Statement	PHI	Chester, Montgomery	39 min
Jul 1, 3:13 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Bucks, Chester, Lehigh, Montgomery	47 min
Jul 1, 3:23 PM EDT	Areal Flood Advisory	PHI	Chester, Montgomery	77 min
Jul 1, 3:50 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Chester, Delaware, Montgomery, Philadelphia	40 min
Jul 1, 4:27 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Delaware, Montgomery, Philadelphia	48 min
Jul 1, 4:59 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Philadelphia	46 min
Jul 1, 5:02 PM EDT	Tornado Warning	PHI	Bucks	28 min
Jun 30, 9:21 PM EDT	Special Weather Statement	PHI	New Castle	39 min
Jul 1, 4:08 PM EDT	Severe Thunderstorm Warning	PHI	Sussex	52 min
Jul 1, 4:08 PM EDT	Severe Thunderstorm Warning	PHI	Kent	52 min
Jul 1, 4:10 PM EDT	Areal Flood Advisory	PHI	Kent, New Castle	94 min
Jul 1, 4:32 PM EDT	Severe Thunderstorm Warning	PHI	Kent, New Castle, Sussex	43 min
Jul 1, 4:57 PM EDT	Tornado Warning	PHI	Kent, Sussex	22 min
Jul 1, 5:12 PM EDT	Severe Thunderstorm Warning	PHI	Kent, Sussex	48 min

Nearby

Areal Flood Advisories in Pennsylvania, 2021 Areal Flood Advisories in Delaware, 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.