Alert archive / Pennsylvania / Areal Flood Advisories in 2020

Areal Flood Advisory 155, NWS Philadelphia/Mount Holly

August 13, 2020Chester County, Montgomery County, Pennsylvania

NWS Philadelphia/Mount Holly issued this areal flood advisory at Aug 13, 2020, 4:45 PM EDT for Chester County, Montgomery County, Pennsylvania. It was in force for 84 min.

The area

The counties it named.

The facts

Issued: Aug 13, 2020, 4:45 PM EDT (20:45 UTC)
Expired: Aug 13, 2020, 6:09 PM EDT
In force: 84 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon

Counties Chester County, PA, Montgomery County, PA

The radar

The Philadelphia radar (KDIX), 99 km from the middle of the area, began a volume at 20:46 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

Washington/Dulle, VA (KIAD), launched 12:00Z, 8.8 hours before the alert went out and 203 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: 646 J/kg
Mixed-layer CIN: -243 J/kg
Mixed-layer LCL: 481 m above ground
0-6 km bulk shear: 19 kt
0-1 km storm-relative helicity: -37 m²/s²
0-3 km storm-relative helicity: -5 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this areal flood advisory went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Philadelphia/Mount Holly wrote its last area forecast discussion before this areal flood advisory went out at Aug 13, 3:54 PM EDT, 51 minutes earlier.

Area forecast discussion, Aug 13, 3:54 PM EDT, 51 minutes before

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Hazardous weather outlook, Aug 13, 3:47 PM EDT, 58 minutes before

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In the hours before

Local storm report, Aug 13, 4:36 PM EDT, 9 minutes before

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Local storm report, Aug 13, 4:37 PM EDT, 8 minutes before

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Local storm report, Aug 13, 4:38 PM EDT, 7 minutes before

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Local storm report, Aug 13, 4:40 PM EDT, 5 minutes before

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Local storm report, Aug 13, 4:41 PM EDT, 4 minutes before

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Local storm report, Aug 13, 4:43 PM EDT, 2 minutes before

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        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
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The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 13, 3:02 AM EDT	Flash Flood Watch	PHI	Atlantic, Burlington, Camden, Cape May, Cumberland, Gloucester and 7 more	17 hr
Aug 13, 7:47 AM EDT	Areal Flood Advisory	PHI	Hunterdon, Mercer, Middlesex, Somerset	118 min
Aug 13, 8:37 AM EDT	Flash Flood Warning	PHI	Hunterdon, Mercer, Middlesex, Somerset	3 hr
Aug 13, 9:36 AM EDT	Areal Flood Advisory	PHI	Hunterdon, Middlesex, Morris, Somerset	114 min
Aug 13, 10:01 AM EDT	Flash Flood Warning	PHI	Middlesex, Morris, Somerset	3 hr
Aug 13, 1:06 PM EDT	Special Weather Statement	PHI	Ocean	39 min
Aug 13, 1:30 PM EDT	Special Weather Statement	PHI	Cumberland	45 min
Aug 13, 1:56 PM EDT	Areal Flood Advisory	PHI	Atlantic, Cape May, Cumberland	2 hr
Aug 13, 1:58 PM EDT	Areal Flood Advisory	PHI	Atlantic, Burlington, Ocean	2 hr
Aug 13, 2:44 PM EDT	Areal Flood Advisory	PHI	Atlantic	2 hr
Aug 13, 3:54 PM EDT	Special Weather Statement	PHI	Cape May	36 min
Aug 13, 4:01 PM EDT	Areal Flood Advisory	PHI	Cape May	2 hr
Aug 13, 4:52 PM EDT	Flash Flood Warning	PHI	Cape May	113 min
Aug 13, 7:25 AM EDT	Areal Flood Advisory	PHI	Bucks, Montgomery	2 hr
Aug 13, 9:07 AM EDT	Flash Flood Warning	PHI	Bucks, Montgomery	3 hr
Aug 13, 3:30 PM EDT	Areal Flood Advisory	PHI	Philadelphia	3 hr
Aug 13, 3:56 PM EDT	Areal Flood Advisory	PHI	Delaware	2 hr
Aug 13, 11:46 AM EDT	Areal Flood Advisory	PHI	New Castle	3 hr
Aug 13, 11:56 AM EDT	Areal Flood Advisory	PHI	Kent, Sussex	3 hr
Aug 13, 12:22 PM EDT	Special Weather Statement	PHI	Sussex	38 min

Nearby

Areal Flood Advisories in Pennsylvania, 2020 Every areal flood advisory in 2020

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.