Alert archive / Pennsylvania / Flash Flood Warnings in 2018

Flash Flood Warning 9, NWS Philadelphia/Mount Holly

May 27, 2018Bucks County, Chester County, Montgomery County, Pennsylvania

NWS Philadelphia/Mount Holly issued this flash flood warning at May 27, 2018, 8:01 AM EDT for Bucks County, Chester County, Montgomery County, 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: May 27, 2018, 8:01 AM EDT (12:01 UTC)
Expired: May 27, 2018, 11:40 AM EDT
In force: 4 hr
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Flood severity: None

Counties Bucks County, PA, Chester County, PA, Montgomery County, PA

The radar

The Philadelphia radar (KDIX), 94 km from the middle of the area, began a volume at 12:03 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, 0.0 hours before the alert went out and 219 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: 51 J/kg
Mixed-layer CIN: -95 J/kg
Mixed-layer LCL: 925 m above ground
0-6 km bulk shear: 26 kt
0-1 km storm-relative helicity: -25 m²/s²
0-3 km storm-relative helicity: 21 m²/s²
Significant tornado parameter: 0.0
Supercell composite: -0.4

Open this sounding in Storm Lab

The text

As transmitted.

599 
WGUS51 KPHI 271201
FFWPHI
PAC017-029-091-271600-
/O.NEW.KPHI.FF.W.0009.180527T1201Z-180527T1600Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Mount Holly NJ
801 AM EDT SUN MAY 27 2018

The National Weather Service in Mount Holly NJ has issued a

* Flash Flood Warning for...
  Central Montgomery County in southeastern Pennsylvania...
  West central Bucks County in southeastern Pennsylvania...
  Northeastern Chester County in southeastern Pennsylvania...

* Until noon EDT.

* At 800 AM EDT, Doppler radar indicated heavy rain across the 
  warned area. Up to three inches of rain has fallen in the last 2 
  hours. Flash flooding is expected to begin shortly in the areas of 
  heaviest rain.

* Some locations that could experience flooding include...
  Norristown, Pottstown, Phoenixville, Lansdale, West Norriton, East
  Norriton, Perkasie, Souderton, Ambler, Collegeville, Royersford,
  Chalfont, Trappe, Hatfield, Schwenksville, Green Lane, Fricks,
  Pughtown, Spring Mount and Lionville-Marchwood.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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

A Flash Flood Warning means that flooding is imminent or occurring.
If you are in the warned area move to higher ground immediately.
Residents living along streams and creeks should take immediate
precautions to protect life and property.

&&

LAT...LON 4039 7527 4017 7516 4008 7545 4003 7568
      4020 7575 4030 7561

$$

MPS

1 follow-up statement

487 
WGUS71 KPHI 271540
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
1140 AM EDT SUN MAY 27 2018

PAC017-029-091-271549-
/O.CAN.KPHI.FF.W.0009.000000T0000Z-180527T1600Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Montgomery PA-Bucks PA-Chester PA-
1140 AM EDT SUN MAY 27 2018

...THE FLASH FLOOD WARNING FOR CENTRAL MONTGOMERY...WEST CENTRAL
BUCKS AND NORTHEASTERN CHESTER COUNTIES IS CANCELLED...

The heavy rain has ended. Flash flooding is no longer expected. The 
Flash Flood Warning has been cancelled.

LAT...LON 4039 7527 4017 7516 4008 7545 4003 7568
      4020 7575 4030 7561

$$

Kruzdlo

The office that day

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

Issued	Product	Office	Counties	Lasted
May 26, 11:38 PM EDT	Flash Flood Watch	PHI	Berks, Bucks, Chester, Delaware, Lehigh, Montgomery and 2 more	23 hr
May 27, 6:33 AM EDT	Flash Flood Warning	PHI	Bucks	4 hr
May 27, 7:30 AM EDT	Flash Flood Warning	PHI	Bucks	4 hr
May 27, 9:17 AM EDT	Areal Flood Advisory	PHI	Bucks	3 hr
May 27, 9:21 AM EDT	River Flood Warning	PHI	Bucks	12 hr
May 27, 9:22 AM EDT	Areal Flood Advisory	PHI	Philadelphia	2 hr
May 27, 9:39 AM EDT	Areal Flood Advisory	PHI	Chester, Delaware, Montgomery	2 hr
May 27, 10:27 AM EDT	Areal Flood Warning	PHI	Bucks	8 hr
May 27, 11:18 AM EDT	Areal Flood Warning	PHI	Bucks	7 hr
May 27, 3:22 PM EDT	Coastal Flood Advisory	PHI	Bucks, Delaware, Philadelphia	12 hr
May 27, 6:07 PM EDT	Areal Flood Warning	PHI	Bucks	4 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; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.