Alert archive / Pennsylvania / Flash Flood Warnings in 2026
Flash Flood Warning 138, NWS Philadelphia/Mount Holly
NWS Philadelphia/Mount Holly issued this flash flood warning at Aug 27, 2026, 5:08 PM EDT for Chester County, Montgomery County, Pennsylvania. It was in force for 4 hr. 4 reports came from inside the area while it was in force.
The area
The outline as issued, with what was reported inside it.
The facts
- Issued
- Aug 27, 2026, 5:08 PM EDT (21:08 UTC)
- Expired
- Aug 27, 2026, 9:09 PM EDT
- In force
- 4 hr
- Issued by
- NWS Philadelphia/Mount Holly
- Area
- Storm-based polygon
- Flood severity
- None
Counties Chester County, PA, Montgomery County, PA
The radar
The Philadelphia radar (KDIX), 114 km from the middle of the area, began a volume at 21:08 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.
What was reported inside it
| Time | Report | Where | Remark |
|---|---|---|---|
| Aug 27, 5:32 PM EDT | FLASH FLOOD | Parkesburg, PA | Multiple water rescues in Parkesburg with water up to vehicle windows. Time given in report. |
| Aug 27, 5:45 PM EDT | FLASH FLOOD | 1 E Atglen, PA | Flooding of Valley Creek at Old Limestone. Creek is overflowing, resulting in road closures nearby. Time estimated. |
| Aug 27, 6:19 PM EDT | RAIN 1.9 | Worcester Twp, PA | Mesonet station CW1648 Worcester. |
| Aug 27, 6:20 PM EDT | FLASH FLOOD | 1 Sse Hatboro, PA | Water rescue reported in Upper Moreland Township. Time estimated. |
Local storm reports filed while the alert was in force, from inside its polygon or its counties.
The nearest sounding before it
Washington/Dulle, VA (KIAD), launched 12:00Z, 9.1 hours before the alert went out and 192 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
- 728 J/kg
- Mixed-layer CIN
- -107 J/kg
- Mixed-layer LCL
- 980 m above ground
- 0-6 km bulk shear
- 33 kt
- 0-1 km storm-relative helicity
- 145 m²/s²
- 0-3 km storm-relative helicity
- 120 m²/s²
- Significant tornado parameter
- 0.2
- Supercell composite
- 2.7
The text
As transmitted.
759
WGUS51 KPHI 272108
FFWPHI
PAC029-091-280115-
/O.NEW.KPHI.FF.W.0138.260827T2108Z-260828T0115Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Mount Holly NJ
Issued by National Weather Service New York NY
508 PM EDT Thu Aug 27 2026
The National Weather Service in Mount Holly has issued a
* Flash Flood Warning for...
Northern Chester County in southeastern Pennsylvania...
Central Montgomery County in southeastern Pennsylvania...
* Until 915 PM EDT.
* At 508 PM EDT, Doppler radar indicated thunderstorms producing
heavy rain across the warned area. Between 1 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 indicated.
IMPACT...Flash flooding of small creeks and streams, urban areas,
highways, streets and underpasses as well as other poor
drainage and low-lying areas.
* Some locations that will experience flash flooding include...
Norristown, Phoenixville, Lansdale, West Norriton, East Norriton,
Coatesville, Downingtown, Hatboro, Ambler, Collegeville, Royersford
and Parkesburg.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Turn around, don't drown when encountering flooded roads. Most flood
deaths occur in vehicles.
&&
LAT...LON 3998 7598 4004 7593 4011 7594 4015 7584
4023 7560 4030 7528 4016 7505 3993 7599
FLASH FLOOD...RADAR INDICATED
EXPECTED RAINFALL RATE...1-2 INCHES IN 1 HOUR
$$
PHI2 follow-up statements
924
WGUS71 KPHI 272332
FFSPHI
Flash Flood Statement
National Weather Service Mount Holly NJ
Issued by National Weather Service New York NY
732 PM EDT Thu Aug 27 2026
PAC029-091-280115-
/O.CON.KPHI.FF.W.0138.000000T0000Z-260828T0115Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Chester PA-Montgomery PA-
732 PM EDT Thu Aug 27 2026
...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 915 PM EDT THIS
EVENING FOR NORTHERN CHESTER AND CENTRAL MONTGOMERY COUNTIES...
At 732 PM EDT, Doppler radar indicated thunderstorms producing heavy
rain across the warned area. Between 3 and 4 inches of rain have
fallen. Additional rainfall amounts up to 0.5 inches are possible in
the warned area. Flash flooding is ongoing or expected to begin
shortly.
HAZARD...Flash flooding caused by thunderstorms.
SOURCE...Radar indicated.
IMPACT...Flash flooding of small creeks and streams, urban areas,
highways, streets and underpasses as well as other poor
drainage and low-lying areas.
Some locations that will experience flash flooding include...
Norristown, Phoenixville, Lansdale, West Norriton, East Norriton,
Coatesville, Downingtown, Hatboro, Ambler, Collegeville, Royersford
and Parkesburg.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Turn around, don't drown when encountering flooded roads. Most flood
deaths occur in vehicles.
&&
LAT...LON 3998 7598 4004 7593 4011 7594 4015 7584
4023 7560 4030 7528 4016 7505 3993 7599
FLASH FLOOD...RADAR INDICATED
$$
PHI788
WGUS71 KPHI 280109
FFSPHI
Flash Flood Statement
National Weather Service Mount Holly NJ
Issued by National Weather Service New York NY
909 PM EDT Thu Aug 27 2026
PAC029-091-280119-
/O.CAN.KPHI.FF.W.0138.000000T0000Z-260828T0115Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Chester PA-Montgomery PA-
909 PM EDT Thu Aug 27 2026
...FLASH FLOOD WARNING FOR NORTHERN CHESTER AND CENTRAL MONTGOMERY
COUNTIES HAS BEEN REPLACED WITH A FLOOD WARNING...
The heavy rain has ended. Flooding is no longer expected to pose a
threat. Please continue to heed remaining road closures. The Flash
Flood Warning has been replaced by an Areal Flood Warning.
A Flood Watch remains in effect until 400 AM EDT Friday for portions
of northern Delaware, New Jersey, and Pennsylvania.
&&
LAT...LON 3998 7598 4004 7593 4011 7594 4015 7584
4023 7560 4030 7528 4016 7505 3993 7599
$$
PHIThe office that day
Everything else NWS Philadelphia/Mount Holly issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 27, 11:38 AM EDT | Flash Flood Warning | PHI | Delaware | 4 hr |
| Aug 27, 1:17 PM EDT | Flash Flood Warning | PHI | Bucks | 7 hr |
| Aug 27, 2:38 PM EDT | Flash Flood Warning | PHI | Delaware, Philadelphia | 4 hr |
| Aug 27, 3:26 PM EDT | Areal Flood Warning | PHI | Delaware | 5 hr |
| Aug 27, 4:06 PM EDT | Severe Thunderstorm Warning | PHI | Chester | 39 min |
| Aug 27, 4:52 PM EDT | Flash Flood Warning | PHI | Northampton | 3 hr |
| Aug 27, 7:00 PM EDT | Flash Flood Warning | PHI | Bucks, Delaware, Montgomery, Philadelphia | 3 hr |
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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.