Alert archive / Delaware / Areal Flood Advisories in 2018

Areal Flood Advisory 252, NWS Philadelphia/Mount Holly

August 20, 2018Sussex County, Delaware

NWS Philadelphia/Mount Holly issued this areal flood advisory at Aug 20, 2018, 3:38 AM EDT for Sussex County, Delaware. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Aug 20, 2018, 3:38 AM EDT (07:38 UTC)
Expired: Aug 20, 2018, 5:56 AM EDT
In force: 2 hr
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon

County Sussex County, DE

The radar

The Dover AFB radar (KDOX), 41 km from the middle of the area, began a volume at 07:40 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

Wallops Is Stn, VA (KWAL), launched 00:00Z, 7.6 hours before the alert went out and 70 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: 1574 J/kg
Mixed-layer CIN: -2 J/kg
Mixed-layer LCL: 622 m above ground
0-6 km bulk shear: 33 kt
0-1 km storm-relative helicity: 53 m²/s²
0-3 km storm-relative helicity: 103 m²/s²
Significant tornado parameter: 0.3
Supercell composite: 3.2

Open this sounding in Storm Lab

The text

As transmitted.

383 
WGUS81 KPHI 200738
FLSPHI

Flood Advisory
National Weather Service Mount Holly NJ
338 AM EDT MON AUG 20 2018

DEC005-201145-
/O.NEW.KPHI.FA.Y.0252.180820T0738Z-180820T1145Z/
/00000.N.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Sussex DE-
338 AM EDT MON AUG 20 2018

The National Weather Service in Mount Holly NJ has issued a

* Flood Advisory for Minor Flooding in Poor Drainage Areas for...
  Southeastern Sussex County in southern Delaware...

* Until 745 AM EDT.

* At 337 AM EDT, Doppler radar indicated heavy rain that will cause
  minor flooding. Overflowing poor drainage areas will result in
  minor flooding in the advisory area. Up to one inch of rain has
  already fallen.

* Some locations that could experience flooding include...
  Millsboro, Selbyville, Dagsboro, Millville, Long Neck, Ocean View,
  Frankford and South Bethany.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Be especially cautious at night when it is harder to recognize the
dangers of flooding.

Excessive runoff from heavy rainfall will cause flooding of small
creeks and streams, country roads, farmland, and other low lying
spots.

Please report flooding to your local law enforcement agency when you
can do so safely.

A Flood Advisory means river or stream flows are elevated, or ponding
of water in urban or other areas is occurring or is imminent.

&&

LAT...LON 3863 7530 3864 7504 3845 7504 3846 7505
      3845 7505 3845 7530

$$

MPS

1 follow-up statement

926 
WGUS81 KPHI 200956
FLSPHI

Flood Advisory
National Weather Service Mount Holly NJ
556 AM EDT MON AUG 20 2018

DEC005-201006-
/O.CAN.KPHI.FA.Y.0252.000000T0000Z-180820T1145Z/
/00000.N.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Sussex DE-
556 AM EDT MON AUG 20 2018

...THE FLOOD ADVISORY HAS BEEN CANCELLED FOR SOUTHEASTERN SUSSEX
COUNTY...

The heavy rain has ended, and flooding is no longer expected to pose
a threat.

LAT...LON 3863 7530 3864 7504 3845 7504 3846 7505
      3845 7505 3845 7530

$$

MPS

Nearby

Areal Flood Advisories in Delaware, 2018 Every areal flood advisory in 2018

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.