Alert archive / Pennsylvania / Flash Flood Warnings in 2026
Flash Flood Warning 117, NWS Philadelphia/Mount Holly
NWS Philadelphia/Mount Holly issued this flash flood warning at Aug 16, 2026, 11:21 PM EDT for 4 counties in Pennsylvania. 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
- Aug 16, 2026, 11:21 PM EDT (03:21 UTC)
- Expired
- Aug 17, 2026, 3:30 AM EDT
- In force
- 4 hr
- Issued by
- NWS Philadelphia/Mount Holly
- Area
- Storm-based polygon
- Flood severity
- None
Counties Chester County, PA, Delaware County, PA, Montgomery County, PA, Philadelphia County, PA
The radar
The Philadelphia radar (KDIX), 91 km from the middle of the area, began a volume at 03:21 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
Brookhaven, NY (KOKX), launched 00:00Z, 3.4 hours before the alert went out and 238 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.
- Mixed-layer CAPE
- 28 J/kg
- Mixed-layer CIN
- -2 J/kg
- Mixed-layer LCL
- 851 m above ground
- 0-6 km bulk shear
- 24 kt
- 0-1 km storm-relative helicity
- 38 m²/s²
- 0-3 km storm-relative helicity
- 63 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
924
WGUS51 KPHI 170321
FFWPHI
PAC029-045-091-101-170730-
/O.NEW.KPHI.FF.W.0117.260817T0321Z-260817T0730Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Mount Holly NJ
1121 PM EDT Sun Aug 16 2026
The National Weather Service in Mount Holly has issued a
* Flash Flood Warning for...
Central Chester County in southeastern Pennsylvania...
Northern Delaware County in southeastern Pennsylvania...
Southern Montgomery County in southeastern Pennsylvania...
Northwestern Philadelphia County in southeastern Pennsylvania...
* Until 330 AM EDT.
* At 1121 PM EDT, Doppler radar indicated heavy rain across the
warned area. Between 1 and 2 inches of rain have fallen. The
expected rainfall rate is 2 to 3 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 heavy rain.
SOURCE...Radar.
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...
Philadelphia, West Chester, Norristown, Phoenixville, West
Norriton, East Norriton, Coatesville, Westtown, Downingtown,
Conshohocken, Royersford and Narberth.
This includes the following highways...
Interstate 476 in Pennsylvania between mile markers 8 and 19.
Interstate 76 in Pennsylvania between mile markers 327 and 338.
Pennsylvania Turnpike between mile markers 305 and 334.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Turn around...don't drown when encountering flooded roads. Most
flood deaths occur in vehicles.
Be especially cautious at night when it is harder to recognize the
dangers of flooding.
&&
LAT...LON 4008 7518 4007 7513 3994 7536 3989 7559
3996 7595 4016 7575 4022 7559
FLASH FLOOD...RADAR INDICATED
EXPECTED RAINFALL RATE...2-3 INCHES IN 1 HOUR
$$
Guzzo2 follow-up statements
824
WGUS71 KPHI 170446
FFSPHI
Flash Flood Statement
National Weather Service Mount Holly NJ
1246 AM EDT Mon Aug 17 2026
PAC029-045-091-101-170730-
/O.CON.KPHI.FF.W.0117.000000T0000Z-260817T0730Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Chester PA-Delaware PA-Montgomery PA-Philadelphia PA-
1246 AM EDT Mon Aug 17 2026
...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 330 AM EDT EARLY THIS
MORNING FOR CENTRAL CHESTER, NORTHERN DELAWARE, SOUTHERN MONTGOMERY
AND NORTHWESTERN PHILADELPHIA COUNTIES...
At 1246 AM EDT, Doppler radar indicated heavy rain across the warned
area. Between 1.5 and 2.5 inches of rain have fallen. Additional
rainfall amounts up to 0.5 inches are possible in the warned area.
Flash flooding is ongoing or expected to begin shortly.
HAZARD...Flash flooding caused by heavy rain.
SOURCE...Radar.
IMPACT...Flooding of small creeks and streams, urban areas,
highways, streets, and underpasses as well as other
drainage and low lying areas.
Some locations that may experience flash flooding include...
Philadelphia, West Chester, Norristown, Phoenixville, West
Norriton, East Norriton, Coatesville, Westtown, Downingtown,
Conshohocken, Royersford and Narberth.
This includes the following highways...
Interstate 476 in Pennsylvania between mile markers 7 and 19.
Interstate 76 in Pennsylvania between mile markers 327 and 338.
Pennsylvania Turnpike between mile markers 305 and 333.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Turn around...don't drown when encountering flooded roads. Most
flood deaths occur in vehicles.
Be especially cautious at night when it is harder to recognize the
dangers of flooding.
&&
LAT...LON 4008 7518 4007 7513 3994 7536 3989 7559
3996 7595 4016 7575 4022 7559
FLASH FLOOD...RADAR INDICATED
$$
Guzzo257
WGUS71 KPHI 170721
FFSPHI
Flash Flood Statement
National Weather Service Mount Holly NJ
321 AM EDT Mon Aug 17 2026
PAC029-045-091-101-170731-
/O.EXP.KPHI.FF.W.0117.000000T0000Z-260817T0730Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Chester PA-Delaware PA-Montgomery PA-Philadelphia PA-
321 AM EDT Mon Aug 17 2026
...FLASH FLOOD WARNING WILL EXPIRE AT 330 AM EDT EARLY THIS MORNING
FOR CENTRAL CHESTER, NORTHERN DELAWARE, SOUTHERN MONTGOMERY AND
NORTHWESTERN PHILADELPHIA COUNTIES...
The heavy rain has ended. Flooding is no longer expected to pose a
threat. Please continue to heed remaining road closures.
&&
LAT...LON 4008 7518 4007 7513 3994 7536 3989 7559
3996 7595 4016 7575 4022 7559
$$
GuzzoThe office that day
Everything else NWS Philadelphia/Mount Holly issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 16, 11:38 PM EDT | Flash Flood Warning | PHI | Bucks, Delaware, Montgomery, Philadelphia | 4 hr |
| Aug 17, 1:57 AM EDT | Flash Flood Warning | PHI | Bucks, Montgomery, Philadelphia | 4 hr |
| Aug 17, 4:43 PM EDT | Special Weather Statement | PHI | Berks | 47 min |
| Aug 17, 5:09 PM EDT | Severe Thunderstorm Warning | PHI | Berks | 36 min |
| Aug 17, 5:30 PM EDT | Special Weather Statement | PHI | Berks | 30 min |
| Aug 17, 6:03 PM EDT | Severe Thunderstorm Warning | PHI | Berks, Chester, Montgomery | 42 min |
| Aug 17, 6:45 PM EDT | Severe Thunderstorm Warning | PHI | Chester, Delaware | 32 min |
Nearby
Flash Flood Warnings in Pennsylvania, 2026Every flash flood warning in 2026
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.