Alert archive / Pennsylvania / Flash Flood Warnings in 2018

Flash Flood Warning 77, NWS Philadelphia/Mount Holly

August 21, 2018Berks County, Chester County, Montgomery County, Pennsylvania

NWS Philadelphia/Mount Holly issued this flash flood warning at Aug 21, 2018, 10:16 PM EDT for Berks County, Chester County, Montgomery County, Pennsylvania. It was in force for 7 hr. 25 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 21, 2018, 10:16 PM EDT (02:16 UTC)
Expired: Aug 22, 2018, 5:15 AM EDT
In force: 7 hr
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Flood severity: None

Counties Berks County, PA, Chester County, PA, Montgomery County, PA

The radar

The Philadelphia radar (KDIX), 132 km from the middle of the area, began a volume at 02:17 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 21, 10:32 PM EDT	FLOOD	Wyomissing, PA	REPORTS OF BASEMENT FLOODING IN WYOMISSING.
Aug 21, 10:59 PM EDT	FLOOD	3 Sw Douglass Twp, PA	U.S. HIGHWAY 422 EASTBOUND AT CHURCH LANE CLOSED FROM FLOODING.
Aug 21, 11:01 PM EDT	FLASH FLOOD	1 S Upper Hanover Twp, PA	THE RIVER GAUGE ON THE WEST BRANCH PERKIOMEN CREEK AT HILLEGASS REACHED FLOOD STAGE.
Aug 21, 11:14 PM EDT	FLASH FLOOD	New Hanover Twp, PA	WATER RESCUE ON HOFFMANSVILLE ROAD IN NEW HANOVER TWP.
Aug 21, 11:28 PM EDT	FLASH FLOOD	1 Wsw Pottstown, PA	WATER RESCUE IN PROGRESS AT HIGH STREET AND MANATAWNY STREET INTERSECTION.
Aug 21, 11:39 PM EDT	FLOOD	1 Wnw Spring Twp, PA	FLOODING ON WERNERSVILLE ROAD IN SOUTH HEIDELBERG TWP.
Aug 21, 11:40 PM EDT	FLOOD	2 N Douglass Twp, PA	FLOODING ON READING AVENUE.
Aug 21, 11:45 PM EDT	FLASH FLOOD	Bechtelsville, PA	WATER RESCUE AT INTERSECTION OF ROUTE 100 AND MILL STREET IN WASHINGTON TWP.
Aug 21, 11:45 PM EDT	FLASH FLOOD	Upper Hanover Twp, PA	THE RIVER GAUGE ON THE PERKIOMEN CREEK AT EAST GREENVILLE REACHED FLOOD STAGE.
Aug 21, 11:49 PM EDT	FLASH FLOOD	2 Se Spring Twp, PA	MUDSLIDE REPORTED AT THE INTERSECTION OF VERMONT RD AND HAMPSHIRE RD IN CUMRU TWP.
Aug 22, 12:00 AM EDT	HEAVY RAIN 3.63	2 Nnw Upper Frederick T, PA
Aug 22, 12:00 AM EDT	HEAVY RAIN 3.8	1 Ese Washington Twp, PA
Aug 22, 12:00 AM EDT	HEAVY RAIN 4.34	2 W Wernersville, PA
Aug 22, 12:43 AM EDT	FLOOD	1 Se South Heidelberg T, PA	FRITZTOWN ROAD CLOSED BETWEEN OLD FRITZTOWN ROAD AND CHAPEL HILL ROAD DUE TO FLOODING.
Aug 22, 12:57 AM EDT	FLOOD	Ontelaunee Twp, PA	SEVERAL ROADS CLOSED IN ONTELAUNEE TWP...INCLUDING LEESPORT AVENUE AND HULLER LANE.
Aug 22, 12:57 AM EDT	FLASH FLOOD	Upper Frederick Twp, PA	WATER RESCUE IN PROGRESS ON FAGLEYSVILLE ROAD.
Aug 22, 1:39 AM EDT	FLASH FLOOD	New Hanover Twp, PA	WATER RESCUE IN PROGRESS ON SWAMP PICNIC ROAD IN NEW HANOVER TWP.
Aug 22, 1:52 AM EDT	FLASH FLOOD	New Hanover Twp, PA	WATER RESCUE IN PROGRESS AT INTERSECTION OF MILES ROAD AND NORTH CHARLOTTE STREET.
Aug 22, 1:54 AM EDT	HEAVY RAIN 2.23	Pottstown Airport, PA	SIX-HOUR RAINFALL TOTAL.
Aug 22, 2:16 AM EDT	FLASH FLOOD	1 Sw Amity Twp, PA	FLOODING ON BASKET ROAD AND MONOCACY CREEK ROAD BETWEEN BEN FRANKLIN HIGHWAY AND GALAHAD LANE. ALL LANES CLOSED.
Aug 22, 2:38 AM EDT	FLASH FLOOD	1 N New Hanover Twp, PA	FLOODING ON STATE HIGHWAY 73 BETWEEN CHARLOTTE STREET AND LAYFIELD ROAD. ALL LANES CLOSED.
Aug 22, 3:26 AM EDT	FLASH FLOOD	Schwenksville, PA	FLOODING ON NEIFFER ROAD AND SCHWENKSVILLE ROAD BETWEEN MAIN STREET AND CEDAR ROAD. ALL LANES CLOSED.
Aug 22, 4:19 AM EDT	FLASH FLOOD	1 W East Greenville, PA	WATER RESCUE IN PROGRESS AT THE INTERSECTIO OF WATER STREET AND STATE STREET.
Aug 22, 4:45 AM EDT	HEAVY RAIN 2.73	Gilbertsville, PA
Aug 22, 5:15 AM EDT	FLOOD	Upper Hanover Twp, PA	WATER STREET IS CLOSED BETWEEN STATE STREET AND ROUTE 29 DUE TO FLOODING.

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 00:00Z, 2.3 hours before the alert went out and 184 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: 509 J/kg
Mixed-layer CIN: -28 J/kg
Mixed-layer LCL: 727 m above ground
0-6 km bulk shear: 41 kt
0-1 km storm-relative helicity: 72 m²/s²
0-3 km storm-relative helicity: 91 m²/s²
Significant tornado parameter: 0.2
Supercell composite: 3.5

Open this sounding in Storm Lab

The text

As transmitted.

797 
WGUS51 KPHI 220216
FFWPHI
PAC011-029-091-220615-
/O.NEW.KPHI.FF.W.0077.180822T0216Z-180822T0615Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Mount Holly NJ
1016 PM EDT TUE AUG 21 2018

The National Weather Service in Mount Holly NJ has issued a

* Flash Flood Warning for...
  Berks County in eastern Pennsylvania...
  Northwestern Montgomery County in southeastern Pennsylvania...
  Central Chester County in southeastern Pennsylvania...

* Until 215 AM EDT.

* At 1014 PM EDT, Doppler radar and automated rain gauges indicated 
  heavy rain falling across the warned area. Up to 1.5 inch of rain 
  have already fallen. Flash flooding is expected to begin shortly 
  in the areas of heaviest rain.

* Some locations that could experience flooding include...
  Reading, West Chester, Pottstown, Phoenixville, Coatesville,
  Wyomissing, Downingtown, Souderton, Birdsboro, Collegeville,
  Royersford, Fleetwood, Sinking Spring, Laureldale, Parkesburg,
  Trappe, East Greenville, Womelsdorf, Wernersville and Newmanstown.

Additional rainfall amounts of 1 to 2 inches are possible in
the warned area. Much of the area is still vulnerable to flooding 
following the recent rounds of excessive rainfall over the past 
several weeks. Therefore, it will not take much additional rainfall 
to produce flash flooding.

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.

Stay away or be swept away. River banks and culverts can become
unstable and unsafe.

&&

LAT...LON 4039 7620 4053 7597 4049 7560 4031 7531
      3999 7552 3984 7602 3987 7599 3993 7600
      3994 7598 3995 7600 4004 7593 4011 7594
      4014 7588 4033 7617 4036 7621

$$

JRK

5 follow-up statements

592 
WGUS71 KPHI 220351
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
1151 PM EDT TUE AUG 21 2018

PAC011-029-091-220615-
/O.CON.KPHI.FF.W.0077.000000T0000Z-180822T0615Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Berks PA-Montgomery PA-Chester PA-
1151 PM EDT TUE AUG 21 2018

...THE FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 215 AM EDT FOR
BERKS...NORTHWESTERN MONTGOMERY AND CENTRAL CHESTER COUNTIES...

At 1147 PM EDT, local law enforcement reported flash flooding in 
Amity Township, Wyomissing, and Washington Twp in Berks County and 
in the Pottstown area in Montgomery County. Several water rescues 
are in progress. Several streams are rising rapidly in the warning 
area with flooding imminent, especially on French Creek in Chester 
County and the West Branch Perkiomen Creek in Montgomery County. Up 
to two and a half inches of rain has fallen in these areas with 
another inch of rain possible. Flash flooding is expected to 
continue for the next few hours.

Some locations that could experience flooding include...
Reading, West Chester, Pottstown, Phoenixville, Coatesville,
Wyomissing, Downingtown, Souderton, Birdsboro, Collegeville,
Royersford, Fleetwood, Sinking Spring, Laureldale, Parkesburg,
Trappe, East Greenville, Womelsdorf, Wernersville and Newmanstown.

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 4039 7620 4053 7597 4049 7560 4031 7531
      3999 7552 3984 7602 3987 7599 3993 7600
      3994 7598 3995 7600 4004 7593 4011 7594
      4014 7588 4033 7617 4036 7621

$$

CMS

596 
WGUS71 KPHI 220521
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
121 AM EDT WED AUG 22 2018

PAC011-029-091-220615-
/O.CON.KPHI.FF.W.0077.000000T0000Z-180822T0615Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Berks PA-Montgomery PA-Chester PA-
121 AM EDT WED AUG 22 2018

...THE FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 215 AM EDT FOR
BERKS...NORTHWESTERN MONTGOMERY AND CENTRAL CHESTER COUNTIES...

At 118 AM EDT, local law enforcement reported flash flooding in 
portions of Berks and Montgomery Counties. A mudslide was reported 
at the intersection of Vermont Road and Hamshire Road in Cumru 
Township, and a water rescue was reported in Upper Frederick 
Township in Montgomery County. The Phoenixville gauge on French 
Creek rose above flood stage in Chester County. Flash flooding will 
continue in the warned area for the next hour.

Some locations that could experience flooding include...
Reading, West Chester, Pottstown, Phoenixville, Coatesville,
Wyomissing, Downingtown, Souderton, Birdsboro, Collegeville,
Royersford, Fleetwood, Sinking Spring, Laureldale, Parkesburg,
Trappe, East Greenville, Womelsdorf, Wernersville and Newmanstown.

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 4039 7620 4053 7597 4049 7560 4031 7531
      3999 7552 3984 7602 3987 7599 3993 7600
      3994 7598 3995 7600 4004 7593 4011 7594
      4014 7588 4033 7617 4036 7621

$$

CMS

561 
WGUS51 KPHI 220601
FFWPHI
PAC011-029-091-220915-
/O.EXT.KPHI.FF.W.0077.000000T0000Z-180822T0915Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Mount Holly NJ
201 AM EDT WED AUG 22 2018

The National Weather Service in Mount Holly NJ has extended the

* Flash Flood Warning for...
  Berks County in eastern Pennsylvania...
  Northwestern Montgomery County in southeastern Pennsylvania...
  Central Chester County in southeastern Pennsylvania...

* Until 515 AM EDT.

* At 159 AM EDT, emergency management reported flash flooding 
  continuing across the warning area. Several water rescues are 
  ongoing in Montgomery County, several small creeks and streams are 
  above flood stage in Montgomery and Chester Counties, and a 
  mudslide has occurred in Cumru Township in Berks County. Though 
  the heavy rainfall has ended, runoff from the rainfall earlier 
  tonight will continue to result in flash flooding for the next 
  several hours.

* Some locations that could experience flooding include...
  Reading, West Chester, Pottstown, Phoenixville, Coatesville,
  Wyomissing, Downingtown, Souderton, Birdsboro, Collegeville,
  Royersford, Fleetwood, Sinking Spring, Laureldale, Parkesburg,
  Trappe, East Greenville, Womelsdorf, Wernersville and Newmanstown.

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 4039 7620 4053 7597 4049 7560 4031 7531
      3999 7552 3984 7602 3987 7599 3993 7600
      3994 7598 3995 7600 4004 7593 4011 7594
      4014 7588 4033 7617 4036 7621

$$

CMS

764 
WGUS71 KPHI 220758
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
358 AM EDT WED AUG 22 2018

PAC011-029-091-220915-
/O.CON.KPHI.FF.W.0077.000000T0000Z-180822T0915Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Berks PA-Montgomery PA-Chester PA-
358 AM EDT WED AUG 22 2018

...THE FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 515 AM EDT FOR
BERKS...NORTHWESTERN MONTGOMERY AND CENTRAL CHESTER COUNTIES...

At 356 AM EDT, local law enforcement reported flash flooding 
continuing in the warned area. Several road closures have been 
reported in Amity Township in Berks County and in Upper Hanover 
Township and Schwenksville in Montgomery County. Additionally, the 
East Branch Brandywine Creek at Downingtown in Chester County is 
rapidly rising at this time. Flash flooding will continue for the 
next couple of hours.

Some locations that could experience flooding include...
Reading, West Chester, Pottstown, Phoenixville, Coatesville,
Wyomissing, Downingtown, Souderton, Birdsboro, Collegeville,
Royersford, Fleetwood, Sinking Spring, Laureldale, Parkesburg,
Trappe, East Greenville, Womelsdorf, Wernersville and Newmanstown.

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 4039 7620 4053 7597 4049 7560 4031 7531
      3999 7552 3984 7602 3987 7599 3993 7600
      3994 7598 3995 7600 4004 7593 4011 7594
      4014 7588 4033 7617 4036 7621

$$

CMS

921 
WGUS71 KPHI 220915
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
515 AM EDT WED AUG 22 2018

PAC011-029-091-220924-
/O.EXP.KPHI.FF.W.0077.000000T0000Z-180822T0915Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Berks PA-Montgomery PA-Chester PA-
515 AM EDT WED AUG 22 2018

...THE FLASH FLOOD WARNING FOR BERKS...NORTHWESTERN MONTGOMERY AND
CENTRAL CHESTER COUNTIES WILL EXPIRE AT 515 AM EDT...

A flood warning has been issued until 915 am. Flooding is expected 
to continue for the next several hours. Please continue to heed all 
road closures this morning.

LAT...LON 4039 7620 4053 7597 4049 7560 4031 7531
      3999 7552 3984 7602 3987 7599 3993 7600
      3994 7598 3995 7600 4004 7593 4011 7594
      4014 7588 4033 7617 4036 7621

$$

CMS

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 21, 8:53 PM EDT	Areal Flood Advisory	PHI	Berks, Chester, Montgomery	5 hr
Aug 21, 10:46 PM EDT	Areal Flood Advisory	PHI	Bucks, Lehigh, Northampton	4 hr
Aug 21, 11:08 PM EDT	Flash Flood Warning	PHI	Bucks, Lehigh, Northampton	4 hr
Aug 21, 11:18 PM EDT	Areal Flood Advisory	PHI	Bucks, Chester, Delaware, Montgomery, Philadelphia	3 hr
Aug 21, 11:47 PM EDT	Areal Flood Advisory	PHI	Northampton	4 hr
Aug 22, 1:14 AM EDT	Areal Flood Advisory	PHI	Monroe	4 hr
Aug 22, 2:54 AM EDT	Areal Flood Warning	PHI	Bucks, Lehigh, Northampton	8 hr
Aug 22, 4:36 AM EDT	River Flood Warning	PHI	Montgomery	6 hr
Aug 22, 5:14 AM EDT	Areal Flood Warning	PHI	Berks, Chester, Montgomery	4 hr
Aug 22, 10:04 AM EDT	River Flood Warning	PHI	Chester, Montgomery, Philadelphia	5 hr

Nearby

Flash Flood Warnings in Pennsylvania, 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.