Alert archive / Pennsylvania / Flash Flood Warnings in 2018

Flash Flood Warning 28, NWS Philadelphia/Mount Holly

July 3, 2018Chester County, Pennsylvania; New Castle County, Delaware; Cecil County, Maryland

NWS Philadelphia/Mount Holly issued this flash flood warning at Jul 3, 2018, 7:54 PM EDT for Chester County, Pennsylvania; New Castle County, Delaware; Cecil County, Maryland. It was in force for 4 hr. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued: Jul 3, 2018, 7:54 PM EDT (23:54 UTC)
Expired: Jul 4, 2018, 12:00 AM EDT
In force: 4 hr
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Flood severity: None

Counties New Castle County, DE, Cecil County, MD, Chester County, PA

The radar

The Dover AFB radar (KDOX), 118 km from the middle of the area, began a volume at 23:53 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 149 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: 574 J/kg
Mixed-layer CIN: -189 J/kg
Mixed-layer LCL: 1257 m above ground
0-6 km bulk shear: 7 kt
0-1 km storm-relative helicity: 14 m²/s²
0-3 km storm-relative helicity: 55 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

328 
WGUS51 KPHI 032354
FFWPHI
DEC003-MDC015-PAC029-040400-
/O.NEW.KPHI.FF.W.0028.180703T2354Z-180704T0400Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Mount Holly NJ
754 PM EDT TUE JUL 3 2018

The National Weather Service in Mount Holly NJ has issued a

* Flash Flood Warning for...
  Northwestern New Castle County in northern Delaware...
  Northern Cecil County in northeastern Maryland...
  Southwestern Chester County in southeastern Pennsylvania...

* Until midnight EDT.

* At 753 PM EDT, Doppler radar indicated thunderstorms producing
  heavy rain across the warned area. Up to one inch of rain has
  already fallen. Flash flooding is expected to begin shortly in the
  areas of heaviest rain.

* Some locations that could experience flooding include...
  Calvert, Oxford, North East, West Grove, Rising Sun, Homeville,
  Glen Roy, Zion, Blake, Cochranville, North Star, West Nottingham,
  Octoraro, Mount Vernon, Fair Hill, Glen Westover, Bay View,
  Lombard, Richardsmere and Woodlawn.

Additional rainfall amounts of two to three inches are possible in 
the warned area.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around...don't drown when encountering flooded roads. Most flood
deaths occur in vehicles.

&&

LAT...LON 3973 7610 3976 7606 3981 7603 3983 7604
      3983 7602 3985 7602 3987 7599 3991 7600
      3993 7597 3976 7570 3954 7607 3965 7616
      3971 7623

$$

SFJ

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 3, 2:15 PM EDT	Special Weather Statement	PHI	Delaware	30 min
Jul 3, 3:00 PM EDT	Special Weather Statement	PHI	Philadelphia	60 min
Jul 3, 3:11 PM EDT	Flash Flood Warning	PHI	Montgomery, Philadelphia	50 min
Jul 3, 4:06 PM EDT	Special Weather Statement	PHI	Montgomery	54 min
Jul 3, 4:30 PM EDT	Special Weather Statement	PHI	Bucks	60 min
Jul 3, 5:24 PM EDT	Areal Flood Advisory	PHI	Delaware, Montgomery, Philadelphia	4 hr
Jul 3, 5:29 PM EDT	Areal Flood Advisory	PHI	Bucks, Montgomery, Philadelphia	4 hr
Jul 3, 5:30 PM EDT	Special Weather Statement	PHI	Philadelphia	30 min
Jul 3, 5:45 PM EDT	Flash Flood Warning	PHI	Delaware, Montgomery, Philadelphia	4 hr
Jul 3, 6:03 PM EDT	Special Weather Statement	PHI	Monroe	57 min
Jul 3, 6:15 PM EDT	Special Weather Statement	PHI	Chester	60 min
Jul 3, 6:18 PM EDT	Severe Thunderstorm Warning	PHI	Delaware, Philadelphia	42 min
Jul 3, 6:21 PM EDT	Special Weather Statement	PHI	Delaware	24 min
Jul 3, 6:25 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Philadelphia	50 min
Jul 3, 6:37 PM EDT	Flash Flood Warning	PHI	Bucks, Philadelphia	3 hr
Jul 3, 6:40 PM EDT	Areal Flood Advisory	PHI	Chester, Delaware	4 hr
Jul 3, 6:50 PM EDT	Special Weather Statement	PHI	Delaware	55 min
Jul 3, 6:54 PM EDT	Severe Thunderstorm Warning	PHI	Chester, Delaware	51 min
Jul 3, 6:58 PM EDT	Flash Flood Warning	PHI	Chester, Delaware	4 hr
Jul 3, 7:03 PM EDT	Special Weather Statement	PHI	Northampton	57 min
Jul 3, 7:06 PM EDT	Flash Flood Warning	PHI	Bucks, Chester, Delaware, Montgomery, Philadelphia	2 hr
Jul 3, 7:22 PM EDT	Severe Thunderstorm Warning	PHI	Chester, Delaware, Montgomery, Philadelphia	21 min
Jul 3, 7:35 PM EDT	Special Weather Statement	PHI	Chester	25 min
Jul 3, 7:39 PM EDT	Severe Thunderstorm Warning	PHI	Chester	51 min

Nearby

Flash Flood Warnings in Pennsylvania, 2018 Flash Flood Warnings in Delaware, 2018 Flash Flood Warnings in Maryland, 2018 Every flash flood warning 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.