Alert archive / Pennsylvania / Flash Flood Warnings in 2017

Flash Flood Warning 26, NWS Philadelphia/Mount Holly

July 23, 20174 counties in Pennsylvania

NWS Philadelphia/Mount Holly issued this flash flood warning at Jul 23, 2017, 7:41 PM EDT for 4 counties in Pennsylvania. It was in force for 6 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: Jul 23, 2017, 7:41 PM EDT (23:41 UTC)
Expired: Jul 24, 2017, 1:45 AM EDT
In force: 6 hr
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Flood severity: None

Counties Bucks County, PA, Delaware County, PA, Montgomery County, PA, Philadelphia County, PA

The radar

The Philadelphia radar (KDIX), 52 km from the middle of the area, began a volume at 23:43 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 12:00Z, 11.7 hours before the alert went out and 201 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 868 m above ground
0-6 km bulk shear: 28 kt
0-1 km storm-relative helicity: -43 m²/s²
0-3 km storm-relative helicity: -8 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

235 
WGUS51 KPHI 232341
FFWPHI
PAC017-045-091-101-240545-
/O.NEW.KPHI.FF.W.0026.170723T2341Z-170724T0545Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Mount Holly NJ
741 PM EDT SUN JUL 23 2017

The National Weather Service in Mount Holly NJ has issued a

* Flash Flood Warning for...
  Southeastern Montgomery County in southeastern Pennsylvania...
  Southeastern Bucks County in southeastern Pennsylvania...
  Philadelphia County in southeastern Pennsylvania...
  Eastern Delaware County in southeastern Pennsylvania...

* Until 145 AM EDT Monday

* At 739 PM EDT...Doppler radar indicated thunderstorms producing 
  heavy rain moving into the warned area from the west. Flash 
  flooding is expected to begin shortly in the areas of heaviest 
  rain.

* Some locations that could experience flooding include...
  Philadelphia, Bensalem, Norristown, Chester, Lansdale, West 
  Norriton, East Norriton, Yeadon, Bristol, Doylestown, 
  Conshohocken, Hatboro, Folcroft, Ambler and Swarthmore.

Rainfall amounts of 2 to 4 inches in a short amount of time are 
possible in the warned area.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Do not drive through flood waters. The water may be deeper than you 
think it is. A vehicle can easily become trapped in flood waters 
endangering its occupants and those who come to their rescue.

If you live in a flood prone location be prepared to move to higher 
ground.

&&

LAT...LON 4012 7478 4013 7482 4008 7487 4005 7497
      3998 7508 3996 7513 3988 7515 3985 7525
      3985 7533 3981 7540 4030 7533 4034 7494
      4030 7487 4024 7483 4022 7477 4015 7472

$$

Iovino

1 follow-up statement

151 
WGUS71 KPHI 240159
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
959 PM EDT SUN JUL 23 2017

PAC017-045-091-101-240208-
/O.CAN.KPHI.FF.W.0026.000000T0000Z-170724T0545Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Montgomery PA-Bucks PA-Philadelphia PA-Delaware PA-
959 PM EDT SUN JUL 23 2017

...THE FLASH FLOOD WARNING FOR SOUTHEASTERN MONTGOMERY...SOUTHEASTERN
BUCKS...PHILADELPHIA AND EASTERN DELAWARE COUNTIES IS CANCELLED...

The heavy rain remained south of the Philadelphia metropolitan area. 
Flooding is no longer expected to pose a threat this evening. 
However, additional heavy rain may move back into the area overnight 
tonight.

LAT...LON 4012 7478 4013 7482 4008 7487 4005 7497
      3998 7508 3996 7513 3988 7515 3985 7525
      3985 7533 3981 7540 4030 7533 4034 7494
      4030 7487 4024 7483 4022 7477 4015 7472

$$

JRK

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 22, 10:52 PM EDT	Areal Flood Advisory	PHI	Bucks	4 hr
Jul 23, 3:16 PM EDT	Flash Flood Watch	PHI	Berks, Bucks, Carbon, Chester, Delaware, Lehigh and 4 more	15 hr
Jul 23, 4:26 PM EDT	Areal Flood Advisory	PHI	Chester	3 hr
Jul 23, 4:48 PM EDT	Areal Flood Advisory	PHI	Chester, Delaware	4 hr
Jul 23, 5:22 PM EDT	Special Weather Statement	PHI	Delaware	23 min
Jul 23, 6:08 PM EDT	Special Weather Statement	PHI	Delaware	37 min
Jul 23, 6:53 PM EDT	Flash Flood Warning	PHI	Chester, Delaware	14 hr
Jul 23, 7:20 PM EDT	Flash Flood Warning	PHI	Berks, Chester, Montgomery	6 hr

Nearby

Flash Flood Warnings in Pennsylvania, 2017 Every flash flood warning in 2017

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.