Alert archive / Pennsylvania / Areal Flood Advisories in 2021

Areal Flood Advisory 96, NWS Philadelphia/Mount Holly

July 25, 2021Chester County, Pennsylvania

NWS Philadelphia/Mount Holly issued this areal flood advisory at Jul 25, 2021, 7:53 PM EDT for Chester County, Pennsylvania. It was in force for 5 hr.

The area

The outline as issued.

The facts

Issued
Jul 25, 2021, 7:53 PM EDT (23:53 UTC)
Expired
Jul 26, 2021, 12:36 AM EDT
In force
5 hr
Issued by
NWS Philadelphia/Mount Holly
Area
Storm-based polygon

County Chester County, PA

The radar

The Dover AFB radar (KDOX), 119 km from the middle of the area, began a volume at 23:54 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, 11.9 hours before the alert went out and 151 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 2021-07-25Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 375 joules per kilogram.LCLLFCEL10008507005003002001001 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 2021-07-25The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 104 square meters per square second.193958Sfc1 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
375 J/kg
Mixed-layer CIN
-92 J/kg
Mixed-layer LCL
780 m above ground
0-6 km bulk shear
36 kt
0-1 km storm-relative helicity
104 m²/s²
0-3 km storm-relative helicity
68 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.3

Open this sounding in Storm Lab

The text

As transmitted.

904 
WGUS81 KPHI 252353
FLSPHI

Flood Advisory
National Weather Service Mount Holly NJ
753 PM EDT Sun Jul 25 2021

PAC029-260400-
/O.NEW.KPHI.FA.Y.0096.210725T2353Z-210726T0400Z/
/00000.N.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Chester PA-
753 PM EDT Sun Jul 25 2021

The National Weather Service in Mount Holly has issued a

* Flood Advisory for...
  Southwestern Chester County in southeastern Pennsylvania...

* Until midnight EDT.

* At 753 PM EDT, Doppler radar indicated heavy rain due to 
  thunderstorms. Minor flooding is ongoing or expected to begin 
  shortly in the advisory area. Between 0.5 and 2 inches of rain 
  have already fallen. Another inch of rain is possible this evening.

* Some locations that may experience flooding include...
  Oxford, West Grove, Homeville, Kemblesville, Mount Vernon, Glen 
  Roy, Ladenberg, and North Star.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3990 7600 3978 7573 3972 7577 3972 7614
      3973 7612 3974 7611 3973 7610 3973 7609
      3975 7610 3976 7608 3976 7606 3980 7604
      3980 7605 3981 7603 3983 7604 3983 7602
      3985 7602 3985 7601 3987 7600 3987 7599

$$

Iovino
2 follow-up statements
062 
WGUS81 KPHI 260152
FLSPHI

Flood Advisory
National Weather Service Mount Holly NJ
952 PM EDT Sun Jul 25 2021

PAC029-260600-
/O.EXT.KPHI.FA.Y.0096.000000T0000Z-210726T0600Z/
/00000.N.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Chester PA-
952 PM EDT Sun Jul 25 2021

The National Weather Service in Mount Holly has extended the

* Flood Advisory for...
  Southwestern Chester County in southeastern Pennsylvania...

* Until 200 AM EDT.

* At 952 PM EDT, Doppler radar indicated heavy rain due to 
  thunderstorms. Minor flooding is ongoing or expected to begin 
  shortly in the advisory area. Between 1 and 3 inches of rain have 
  already fallen. Another inch of rain is possible.

* Some locations that may experience flooding include...
  Oxford, West Grove, Homeville, Kemblesville, Mount Vernon, Glen 
  Roy, Landenberg, and North Star.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3990 7600 3978 7573 3972 7577 3972 7614
      3973 7612 3974 7611 3973 7610 3973 7609
      3975 7610 3976 7608 3976 7606 3980 7604
      3980 7605 3981 7603 3983 7604 3983 7602
      3985 7602 3985 7601 3987 7600 3987 7599

$$

Iovino
920 
WGUS81 KPHI 260436
FLSPHI

Flood Advisory
National Weather Service Mount Holly NJ
1236 AM EDT Mon Jul 26 2021

PAC029-260446-
/O.CAN.KPHI.FA.Y.0096.000000T0000Z-210726T0600Z/
/00000.N.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Chester PA-
1236 AM EDT Mon Jul 26 2021

...FLOOD ADVISORY IS CANCELLED FOR SOUTHWESTERN CHESTER COUNTY...

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

LAT...LON 3990 7600 3978 7573 3972 7577 3972 7614
      3973 7612 3974 7611 3973 7610 3973 7609
      3975 7610 3976 7608 3976 7606 3980 7604
      3980 7605 3981 7603 3983 7604 3983 7602
      3985 7602 3985 7601 3987 7600 3987 7599

$$

JEO

The office that day

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

IssuedProductOfficeCountiesLasted
Jul 25, 3:43 PM EDTSpecial Weather StatementPHIChester47 min

Nearby

Areal Flood Advisories in Pennsylvania, 2021Every 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.