Alert archive / Delaware / Flash Flood Warnings in 2025

Flash Flood Warning 92, NWS Philadelphia/Mount Holly

August 13, 2025New Castle County, Delaware; Chester County, Pennsylvania

NWS Philadelphia/Mount Holly issued this flash flood warning at Aug 13, 2025, 6:59 PM EDT for New Castle County, Delaware; Chester County, Pennsylvania. It was in force for 2 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: Aug 13, 2025, 6:59 PM EDT (22:59 UTC)
Expired: Aug 13, 2025, 9:25 PM EDT
In force: 2 hr
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Flood severity: None

Counties New Castle County, DE, Chester County, PA

The radar

The Dover AFB radar (KDOX), 115 km from the middle of the area, began a volume at 22:58 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, 11.0 hours before the alert went out and 159 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: 1496 J/kg
Mixed-layer CIN: -47 J/kg
Mixed-layer LCL: 719 m above ground
0-6 km bulk shear: 27 kt
0-1 km storm-relative helicity: 19 m²/s²
0-3 km storm-relative helicity: 47 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.2

Open this sounding in Storm Lab

The text

As transmitted.

869 
WGUS51 KPHI 132259
FFWPHI
DEC003-PAC029-140300-
/O.NEW.KPHI.FF.W.0092.250813T2259Z-250814T0300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Mount Holly NJ
659 PM EDT Wed Aug 13 2025

The National Weather Service in Mount Holly has issued a

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

* Until 1100 PM EDT.

* At 659 PM EDT, Doppler radar and automated rain gauges indicated 
  thunderstorms producing heavy rain across the warned area. Between 
  0.5 and 2 inches of rain have fallen. The expected rainfall rate 
  is 1 to 2 inches in 1 hour. Additional rainfall amounts of 1 to 2 
  inches are possible in the warned area. Flash flooding is ongoing 
  or expected to begin shortly.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Radar and automated gauges.

  IMPACT...Flooding of small creeks and streams, urban areas,
           highways, streets, and underpasses as well as other
           drainage and low lying areas.

* Some locations that may experience flash flooding include...
  Wilmington, Newark, Elsmere, Kennett Square, Oxford, West Grove, 
  Newport, Landenberg, Kemblesville, North Star, Pike Creek and 
  Hockessin.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

In hilly terrain there are hundreds of low water crossings which are 
potentially dangerous in heavy rain. Do not attempt to cross flooded 
roads. Find an alternate route.

&&

LAT...LON 3972 7579 3972 7614 3974 7611 3973 7610
      3975 7610 3976 7606 3983 7604 3983 7602
      3985 7602 3985 7601 3987 7600 3987 7599
      3989 7599 3990 7599 3990 7585 3985 7559
      3984 7560 3983 7549 3961 7570 3962 7579

FLASH FLOOD...RADAR AND GAUGE INDICATED
EXPECTED RAINFALL RATE...1-2 INCHES IN 1 HOUR

$$

Staarmann

2 follow-up statements

084 
WGUS71 KPHI 132347
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
747 PM EDT Wed Aug 13 2025

DEC003-PAC029-140300-
/O.CON.KPHI.FF.W.0092.000000T0000Z-250814T0300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
New Castle DE-Chester PA-
747 PM EDT Wed Aug 13 2025

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 11 PM EDT THIS 
EVENING FOR NORTHWESTERN NEW CASTLE AND SOUTHWESTERN CHESTER 
COUNTIES...

At 747 PM EDT, Doppler radar and automated rain gauges indicated 
thunderstorms producing heavy rain across the warned area. Between 
0.5 and 3 inches of rain have fallen. The expected rainfall rate is 
0.5 to 1.5 inches in 1 hour. Additional rainfall amounts of 0.5 to 1 
inch are possible in the warned area. Flash flooding is ongoing or 
expected to begin shortly.

HAZARD...Flash flooding caused by thunderstorms.

SOURCE...Radar and automated gauges.

IMPACT...Flooding of small creeks and streams, urban areas,
         highways, streets, and underpasses as well as other
         drainage and low lying areas.

Some locations that may experience flash flooding include...
  Wilmington, Newark, Elsmere, Kennett Square, Oxford, West Grove, 
  Newport, Landenberg, Kemblesville, North Star, Pike Creek and 
  Hockessin.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

In hilly terrain there are hundreds of low water crossings which are 
potentially dangerous in heavy rain. Do not attempt to cross flooded 
roads. Find an alternate route.

Please report observed flooding to local emergency services or law 
enforcement and request they pass this information to the National 
Weather Service when you can do so safely.

&&

LAT...LON 3972 7579 3972 7614 3974 7611 3973 7610
      3975 7610 3976 7606 3983 7604 3983 7602
      3985 7602 3985 7601 3987 7600 3987 7599
      3989 7599 3990 7599 3990 7585 3985 7559
      3984 7560 3983 7549 3961 7570 3962 7579

FLASH FLOOD...RADAR AND GAUGE INDICATED
EXPECTED RAINFALL RATE...0.5-1.5 INCHES IN 1 HOUR

$$

Staarmann

133 
WGUS71 KPHI 140125
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
925 PM EDT Wed Aug 13 2025

DEC003-PAC029-140135-
/O.CAN.KPHI.FF.W.0092.000000T0000Z-250814T0300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
New Castle DE-Chester PA-
925 PM EDT Wed Aug 13 2025

...FLASH FLOOD WARNING IS CANCELLED FOR NORTHWESTERN NEW CASTLE AND 
SOUTHWESTERN CHESTER COUNTIES...

The heavy rain has ended. Flooding is no longer expected to pose a 
threat. Please continue to heed remaining road closures.

&&

LAT...LON 3972 7579 3972 7614 3974 7611 3973 7610
      3975 7610 3976 7606 3983 7604 3983 7602
      3985 7602 3985 7601 3987 7600 3987 7599
      3989 7599 3990 7599 3990 7585 3985 7559
      3984 7560 3983 7549 3961 7570 3962 7579

$$

Staarmann

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 13, 12:07 PM EDT	Flood Watch	PHI	New Castle	9 hr
Aug 13, 6:26 PM EDT	Severe Thunderstorm Warning	PHI	New Castle	49 min
Aug 13, 4:49 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Lehigh, Northampton	41 min
Aug 13, 6:54 PM EDT	Flash Flood Warning	PHI	Bucks, Montgomery, Philadelphia	2 hr

Nearby

Flash Flood Warnings in Delaware, 2025 Flash Flood Warnings in Pennsylvania, 2025 Every flash flood warning in 2025

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.