Alert archive / Pennsylvania / Flash Flood Warnings in 2017

Flash Flood Warning 39, NWS Philadelphia/Mount Holly

August 2, 2017Montgomery County, Pennsylvania

NWS Philadelphia/Mount Holly issued this flash flood warning at Aug 2, 2017, 1:48 PM EDT for 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: Aug 2, 2017, 1:48 PM EDT (17:48 UTC)
Expired: Aug 2, 2017, 5:45 PM EDT
In force: 4 hr
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Flood severity: None

County Montgomery County, PA

The radar

The Philadelphia radar (KDIX), 85 km from the middle of the area, began a volume at 17:49 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, 5.8 hours before the alert went out and 217 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: 378 J/kg
Mixed-layer CIN: -76 J/kg
Mixed-layer LCL: 1469 m above ground
0-6 km bulk shear: 20 kt
0-1 km storm-relative helicity: 18 m²/s²
0-3 km storm-relative helicity: 37 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

743 
WGUS51 KPHI 021748
FFWPHI
PAC091-022145-
/O.NEW.KPHI.FF.W.0039.170802T1748Z-170802T2145Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Mount Holly NJ
148 PM EDT WED AUG 2 2017

The National Weather Service in Mount Holly NJ has issued a

* Flash Flood Warning for...
  Central Montgomery County in southeastern Pennsylvania...

* Until 545 PM EDT

* At 148 PM EDT...Doppler radar indicated thunderstorms producing
  heavy rain across the warned area. Up to two inches 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...
  Norristown, Lansdale, West Norriton, East Norriton, Conshohocken,
  Ambler, Collegeville, Plymouth Meeting, King Of Prussia, Bryn Mawr,
  Skippack, Bridgeport, North Wales, West Conshohocken, Evansburg,
  Audubon, Blue Bell, Maple Glen, Eagleville and Spring House.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4028 7533 4020 7516 4002 7530 4005 7535
      4007 7536 4006 7538 4009 7542 4011 7547
      4013 7547 4013 7550 4014 7551

$$

Kruzdlo

1 follow-up statement

599 
WGUS71 KPHI 021933
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
333 PM EDT WED AUG 2 2017

PAC091-021941-
/O.CAN.KPHI.FF.W.0039.000000T0000Z-170802T2145Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Montgomery PA-
333 PM EDT WED AUG 2 2017

...THE FLASH FLOOD WARNING FOR CENTRAL MONTGOMERY COUNTY IS
CANCELLED...

The heaviest rains have ended. The flash flood warning has been 
cancelled. A flood advisory still remains in effect for portions of 
the county.

LAT...LON 4028 7533 4020 7516 4002 7530 4005 7535
      4007 7536 4006 7538 4009 7542 4011 7547
      4013 7547 4013 7550 4014 7551

$$

Kruzdlo

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 2, 12:09 PM EDT	Special Weather Statement	PHI	Philadelphia	36 min
Aug 2, 12:11 PM EDT	Special Weather Statement	PHI	Monroe	34 min
Aug 2, 12:28 PM EDT	Areal Flood Advisory	PHI	Bucks, Chester, Delaware, Montgomery, Philadelphia	4 hr
Aug 2, 12:39 PM EDT	Areal Flood Advisory	PHI	Monroe	4 hr
Aug 2, 12:45 PM EDT	Areal Flood Advisory	PHI	Carbon, Monroe	4 hr
Aug 2, 12:52 PM EDT	Special Weather Statement	PHI	Monroe	23 min
Aug 2, 12:53 PM EDT	Special Weather Statement	PHI	Carbon	37 min
Aug 2, 12:55 PM EDT	Special Weather Statement	PHI	Delaware	35 min
Aug 2, 1:08 PM EDT	Special Weather Statement	PHI	Philadelphia	37 min
Aug 2, 1:26 PM EDT	Special Weather Statement	PHI	Delaware	34 min
Aug 2, 1:30 PM EDT	Severe Thunderstorm Warning	PHI	Chester, Delaware, Montgomery, Philadelphia	30 min
Aug 2, 1:36 PM EDT	Special Weather Statement	PHI	Bucks	39 min
Aug 2, 1:49 PM EDT	Special Weather Statement	PHI	Lehigh	41 min
Aug 2, 1:50 PM EDT	Special Weather Statement	PHI	Philadelphia	25 min
Aug 2, 2:01 PM EDT	Areal Flood Advisory	PHI	Bucks	4 hr
Aug 2, 2:04 PM EDT	Severe Thunderstorm Warning	PHI	Bucks	41 min
Aug 2, 2:09 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Lehigh, Montgomery	51 min
Aug 2, 2:16 PM EDT	Areal Flood Advisory	PHI	Berks	4 hr
Aug 2, 2:27 PM EDT	Areal Flood Advisory	PHI	Bucks, Chester, Montgomery	4 hr
Aug 2, 2:37 PM EDT	Special Weather Statement	PHI	Berks	38 min
Aug 2, 2:45 PM EDT	Areal Flood Advisory	PHI	Monroe, Northampton	4 hr
Aug 2, 2:48 PM EDT	Severe Thunderstorm Warning	PHI	Monroe, Northampton	27 min
Aug 2, 3:04 PM EDT	Severe Thunderstorm Warning	PHI	Lehigh, Northampton	41 min
Aug 2, 3:12 PM EDT	Special Weather Statement	PHI	Montgomery	48 min
Aug 2, 3:34 PM EDT	Special Weather Statement	PHI	Chester	26 min
Aug 2, 4:09 PM EDT	Areal Flood Advisory	PHI	Monroe	4 hr
Aug 2, 4:23 PM EDT	Special Weather Statement	PHI	Monroe	37 min
Aug 2, 4:27 PM EDT	Areal Flood Advisory	PHI	Delaware, Philadelphia	4 hr
Aug 2, 4:40 PM EDT	Special Weather Statement	PHI	Philadelphia	50 min

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.