Alert archive / Pennsylvania / Areal Flood Advisories in 2018

Areal Flood Advisory 310, NWS Philadelphia/Mount Holly

September 26, 2018Berks County, Chester County, Montgomery County, Pennsylvania; Cecil County, Maryland

NWS Philadelphia/Mount Holly issued this areal flood advisory at Sep 26, 2018, 7:31 PM EDT for Berks County, Chester County, Montgomery County, Pennsylvania; Cecil County, Maryland. It was in force for 106 min.

The area

The outline as issued.

The facts

Issued: Sep 26, 2018, 7:31 PM EDT (23:31 UTC)
Expired: Sep 26, 2018, 9:17 PM EDT
In force: 106 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon

Counties Cecil County, MD, Berks County, PA, Chester County, PA, Montgomery County, PA

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 11.5 hours before the alert went out and 164 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: 6 J/kg
Mixed-layer CIN: -201 J/kg
Mixed-layer LCL: 948 m above ground
0-6 km bulk shear: 20 kt
0-1 km storm-relative helicity: 99 m²/s²
0-3 km storm-relative helicity: 111 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.1

Open this sounding in Storm Lab

The text

As transmitted.

380 
WGUS81 KPHI 262331
FLSPHI

Flood Advisory
National Weather Service Mount Holly NJ
731 PM EDT WED SEP 26 2018

MDC015-PAC011-029-091-270330-
/O.NEW.KPHI.FA.Y.0310.180926T2331Z-180927T0330Z/
/00000.N.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Cecil MD-Berks PA-Montgomery PA-Chester PA-
731 PM EDT WED SEP 26 2018

The National Weather Service in Mount Holly NJ has issued a

* Flood Advisory for...
  Northern Cecil County in northeastern Maryland...
  Southeastern Berks County in eastern Pennsylvania...
  Northwestern Montgomery County in southeastern Pennsylvania...
  Chester County in southeastern Pennsylvania...

* Until 1130 PM EDT.

* At 730 PM EDT, Doppler radar indicated heavy rain due to 
  thunderstorms will move into the advisory area. This will cause 
  minor flooding in the advisory area. Up to one inch of rain should 
  fall in the next hour or so.

* Some locations that could experience flooding include...
  Calvert, Pottstown, Phoenixville, Coatesville, Downingtown, Kennett
  Square, Birdsboro, Collegeville, Oxford, Royersford, Parkesburg,
  North East, Trappe, West Grove, Rising Sun, Honey Brook,
  Schwenksville, Elverson, Charlestown and Bechtelsville.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Be especially cautious at night when it is harder to recognize the
dangers of flooding.

Excessive runoff from heavy rainfall will cause flooding of small
creeks and streams, urban areas, highways, streets and underpasses as
well as other drainage areas and low lying spots.

Excessive runoff from heavy rainfall will cause flooding of small
creeks and streams, country roads, farmland, and other low lying
spots.

Please report flooding to your local law enforcement agency when you
can do so safely.

A Flood Advisory means river or stream flows are elevated, or ponding
of water in urban or other areas is occurring or is imminent.

&&

LAT...LON 3972 7623 3973 7610 3987 7599 3993 7600
      3994 7598 3995 7600 4004 7593 4011 7594
      4014 7588 4022 7599 4044 7580 4029 7538
      3951 7598 3953 7598 3955 7605

$$

MPS

2 follow-up statements

841 
WGUS81 KPHI 270012
FLSPHI

Flood Advisory
National Weather Service Mount Holly NJ
812 PM EDT WED SEP 26 2018

PAC011-091-270021-
/O.CAN.KPHI.FA.Y.0310.000000T0000Z-180927T0330Z/
/00000.N.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Berks PA-Montgomery PA-
812 PM EDT WED SEP 26 2018

...THE FLOOD ADVISORY HAS BEEN CANCELLED FOR SOUTHEASTERN BERKS AND
NORTHWESTERN MONTGOMERY COUNTIES...

The heavy rain has ended. Therefore, the flooding threat has ended.

LAT...LON 3972 7623 3973 7610 3976 7606 3987 7599
      3992 7600 3994 7598 3995 7600 4004 7593
      4011 7594 4014 7587 4009 7554 3951 7598
      3953 7598 3955 7605

$$

MDC015-PAC029-270330-
/O.CON.KPHI.FA.Y.0310.000000T0000Z-180927T0330Z/
/00000.N.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Cecil MD-Chester PA-
812 PM EDT WED SEP 26 2018

...THE FLOOD ADVISORY REMAINS IN EFFECT UNTIL 1130 PM EDT FOR
NORTHERN CECIL AND CHESTER COUNTIES...

At 811 PM EDT, Doppler radar indicated heavy rain due to
thunderstorms. This will cause minor flooding in the advisory area.
Up to one inch of rain has already fallen. Up to one inch of rain 
has fallen, and heavy rain continues in the advisory area.

Some locations that could experience flooding include...
Calvert, Coatesville, Downingtown, Oxford, Parkesburg, North East,
West Grove, Rising Sun, Honey Brook, Charlestown, Homeville, Glen
Roy, Zion, Blake, Cochranville, West Nottingham, Octoraro, Mount
Vernon, Marshallton and Fair Hill.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Be especially cautious at night when it is harder to recognize the
dangers of flooding.

Excessive runoff from heavy rainfall will cause flooding of small
creeks and streams, urban areas, highways, streets and underpasses as
well as other drainage areas and low lying spots.

Excessive runoff from heavy rainfall will cause flooding of small
creeks and streams, country roads, farmland, and other low lying
spots.

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 flooding to your local law enforcement agency when you
can do so safely.

A Flood Advisory means river or stream flows are elevated, or ponding
of water in urban or other areas is occurring or is imminent.

&&

LAT...LON 3972 7623 3973 7610 3976 7606 3987 7599
      3992 7600 3994 7598 3995 7600 4004 7593
      4011 7594 4014 7587 4009 7554 3951 7598
      3953 7598 3955 7605

$$

MPS

464 
WGUS81 KPHI 270117 RRA
FLSPHI

Flood Advisory
National Weather Service Mount Holly NJ
917 PM EDT WED SEP 26 2018

MDC015-PAC029-270127-
/O.CAN.KPHI.FA.Y.0310.000000T0000Z-180927T0330Z/
/00000.N.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Cecil MD-Chester PA-
917 PM EDT WED SEP 26 2018

...THE FLOOD ADVISORY HAS BEEN CANCELLED FOR NORTHERN CECIL AND
CHESTER COUNTIES...

The heavy rain has ended, and flooding is no longer expected to pose
a threat.

LAT...LON 3972 7623 3973 7610 3976 7606 3987 7599
      3992 7600 3994 7598 3995 7600 4004 7593
      4011 7594 4014 7587 4009 7554 3951 7598
      3953 7598 3955 7605

$$

MPS

The office that day

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

Issued	Product	Office	Counties	Lasted
Sep 25, 9:11 PM EDT	Areal Flood Warning	PHI	Philadelphia	3 hr
Sep 26, 6:15 PM EDT	Special Weather Statement	PHI	Northampton	30 min
Sep 26, 6:37 PM EDT	Special Weather Statement	PHI	Chester	53 min
Sep 26, 6:41 PM EDT	Areal Flood Advisory	PHI	Carbon, Lehigh, Monroe, Northampton	3 hr
Sep 26, 7:06 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Chester, Delaware, Montgomery	54 min
Sep 26, 7:53 PM EDT	Severe Thunderstorm Warning	PHI	Chester	52 min
Sep 26, 7:16 PM EDT	Severe Thunderstorm Warning	PHI	Caroline, Cecil, Kent, Queen Anne's, Talbot	43 min

Nearby

Areal Flood Advisories in Pennsylvania, 2018 Areal Flood Advisories in Maryland, 2018 Every areal flood advisory 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.