Alert archive / Pennsylvania / Areal Flood Advisories in 2021

Areal Flood Advisory 28, NWS Philadelphia/Mount Holly

June 9, 2021Chester County, Pennsylvania

NWS Philadelphia/Mount Holly issued this areal flood advisory at Jun 9, 2021, 8:43 PM EDT for Chester County, Pennsylvania. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued
Jun 9, 2021, 8:43 PM EDT (00:43 UTC)
Expired
Jun 9, 2021, 10:55 PM EDT
In force
2 hr
Issued by
NWS Philadelphia/Mount Holly
Area
Storm-based polygon

County Chester County, PA

The radar

The Dover AFB radar (KDOX), 127 km from the middle of the area, began a volume at 00:45 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, 0.7 hours before the alert went out and 165 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 00:00Z on 2021-06-10Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 186 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Washington/Dulle, VA at 00:00Z on 2021-06-10The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 37 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
186 J/kg
Mixed-layer CIN
-73 J/kg
Mixed-layer LCL
1395 m above ground
0-6 km bulk shear
11 kt
0-1 km storm-relative helicity
37 m²/s²
0-3 km storm-relative helicity
30 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

367 
WGUS81 KPHI 100043
FLSPHI

Flood Advisory
National Weather Service Mount Holly NJ
843 PM EDT Wed Jun 9 2021

PAC029-100345-
/O.NEW.KPHI.FA.Y.0028.210610T0043Z-210610T0345Z/
/00000.N.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Chester PA-
843 PM EDT Wed Jun 9 2021

The National Weather Service in Mount Holly has issued a

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

* Until 1145 PM EDT.

* At 843 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 1.5 inches of rain 
  have fallen in spots.

* Some locations that may experience flooding include...
  West Chester, Coatesville, Downingtown, Kennett Square, Oxford, 
  Parkesburg, West Grove, Honey Brook, Cochranville, Marshallton, 
  Ladenberg, and Homeville.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3997 7558 3985 7566 3976 7580 3981 7604
      3981 7603 3983 7604 3982 7603 3983 7602
      3985 7602 3985 7601 3987 7600 3987 7599
      3991 7600 3993 7600 3993 7598 3995 7599
      4004 7593 4011 7594 4014 7586

$$

Iovino
1 follow-up statement
155 
WGUS81 KPHI 100255
FLSPHI

Flood Advisory
National Weather Service Mount Holly NJ
1055 PM EDT Wed Jun 9 2021

PAC029-100305-
/O.CAN.KPHI.FA.Y.0028.000000T0000Z-210610T0345Z/
/00000.N.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Chester PA-
1055 PM EDT Wed Jun 9 2021

...FLOOD ADVISORY IS CANCELLED FOR CENTRAL 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 3997 7558 3985 7566 3976 7580 3981 7604
      3981 7603 3983 7604 3982 7603 3983 7602
      3985 7602 3985 7601 3987 7600 3987 7599
      3991 7600 3993 7600 3993 7598 3995 7599
      4004 7593 4011 7594 4014 7586

$$

SFJ

The office that day

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

IssuedProductOfficeCountiesLasted
Jun 9, 8:21 PM EDTSevere Thunderstorm WarningPHIChester39 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.