Alert archive / Pennsylvania / Areal Flood Advisories in 2021

Areal Flood Advisory 151, NWS Philadelphia/Mount Holly

August 27, 2021Chester County, Pennsylvania

NWS Philadelphia/Mount Holly issued this areal flood advisory at Aug 27, 2021, 2:18 PM EDT for Chester County, Pennsylvania. It was in force for 93 min.

The area

The outline as issued.

The facts

Issued: Aug 27, 2021, 2:18 PM EDT (18:18 UTC)
Expired: Aug 27, 2021, 3:51 PM EDT
In force: 93 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon

County Chester County, PA

The radar

The Philadelphia radar (KDIX), 111 km from the middle of the area, began a volume at 18:18 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, 6.3 hours before the alert went out and 188 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: 780 J/kg
Mixed-layer CIN: -92 J/kg
Mixed-layer LCL: 983 m above ground
0-6 km bulk shear: 8 kt
0-1 km storm-relative helicity: 13 m²/s²
0-3 km storm-relative helicity: 41 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

321 
WGUS81 KPHI 271818
FLSPHI

Flood Advisory
National Weather Service Mount Holly NJ
218 PM EDT Fri Aug 27 2021

PAC029-272130-
/O.NEW.KPHI.FA.Y.0151.210827T1818Z-210827T2130Z/
/00000.N.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Chester PA-
218 PM EDT Fri Aug 27 2021

The National Weather Service in Mount Holly has issued a

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

* Until 530 PM EDT.

* At 218 PM EDT, Doppler radar indicated heavy rain due to 
  thunderstorms. Minor flooding is ongoing or expected to begin 
  shortly in the advisory area. Between 1.5 and 2 inches of rain 
  have fallen.

* Some locations that may experience flooding include...
  West Chester, Coatesville, Downingtown, Parkesburg, Marshallton, 
  Lionville, Lionville-Marchwood, West Goshen, South Coatesville, 
  Modena, Thorndale, and Exton.

This includes the following highways...
	Pennsylvania Turnpike between mile markers 312 and 315.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4007 7565 4007 7561 3996 7557 3992 7591
      4007 7590

$$

Kruzdlo

1 follow-up statement

200 
WGUS81 KPHI 271951
FLSPHI

Flood Advisory
National Weather Service Mount Holly NJ
351 PM EDT Fri Aug 27 2021

PAC029-272001-
/O.CAN.KPHI.FA.Y.0151.000000T0000Z-210827T2130Z/
/00000.N.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Chester PA-
351 PM EDT Fri Aug 27 2021

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

The heavy rain has ended. At this time, flooding is no longer 
expected to pose a threat. More thunderstorms are expected into the 
evening which may prompt additional flood advisories or warnings.

LAT...LON 4007 7565 4007 7561 3996 7557 3992 7591
      4007 7590

$$

Kruzdlo

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 27, 1:20 PM EDT	Areal Flood Advisory	PHI	Carbon, Monroe	2 hr
Aug 27, 1:33 PM EDT	Areal Flood Advisory	PHI	Bucks, Delaware, Philadelphia	83 min
Aug 27, 1:36 PM EDT	Special Weather Statement	PHI	Monroe	24 min
Aug 27, 1:52 PM EDT	Severe Thunderstorm Warning	PHI	Chester	53 min
Aug 27, 2:12 PM EDT	Special Weather Statement	PHI	Northampton	33 min
Aug 27, 2:32 PM EDT	Severe Thunderstorm Warning	PHI	Carbon, Monroe, Northampton	28 min
Aug 27, 2:33 PM EDT	Areal Flood Advisory	PHI	Carbon, Monroe, Northampton	109 min
Aug 27, 2:42 PM EDT	Severe Thunderstorm Warning	PHI	Chester	14 min
Aug 27, 3:07 PM EDT	Severe Thunderstorm Warning	PHI	Northampton	24 min
Aug 27, 3:44 PM EDT	Special Weather Statement	PHI	Delaware	31 min
Aug 27, 5:29 PM EDT	Areal Flood Advisory	PHI	Bucks, Montgomery	3 hr
Aug 27, 6:29 PM EDT	Areal Flood Advisory	PHI	Berks	3 hr
Aug 27, 6:41 PM EDT	Special Weather Statement	PHI	Berks	34 min
Aug 27, 7:17 PM EDT	Flash Flood Warning	PHI	Berks	3 hr

Nearby

Areal Flood Advisories in Pennsylvania, 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.