Alert archive / Pennsylvania / Flash Flood Warnings in 2022

Flash Flood Warning 17, NWS Philadelphia/Mount Holly

September 6, 2022Chester County, Montgomery County, Pennsylvania

NWS Philadelphia/Mount Holly issued this flash flood warning at Sep 6, 2022, 6:32 AM EDT for Chester County, Montgomery County, Pennsylvania. It was in force for 4 hr. 3 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: Sep 6, 2022, 6:32 AM EDT (10:32 UTC)
Expired: Sep 6, 2022, 10:45 AM EDT
In force: 4 hr
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Flood severity: None

Counties Chester County, PA, Montgomery County, PA

The radar

The Philadelphia radar (KDIX), 96 km from the middle of the area, began a volume at 10:36 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
Sep 6, 7:00 AM EDT	FLASH FLOOD	West Chester, PA	EAST BARNARD STREET WAS CLOSED BETWEEN SOUTH MATLACK STREET AND SOUTH FRANKLIN STREET DUE TO FLOODING.
Sep 6, 7:00 AM EDT	FLASH FLOOD	West Chester, PA	SOUTH ADAMS STREET WAS CLOSED BETWEEN EAST MARKET STREET AND EAST MINER STREET DUE TO FLOODING.
Sep 6, 8:00 AM EDT	HEAVY RAIN 4.8	Skippack Twp, PA

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, 10.5 hours before the alert went out and 207 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: 282 J/kg
Mixed-layer CIN: -8 J/kg
Mixed-layer LCL: 828 m above ground
0-6 km bulk shear: 26 kt
0-1 km storm-relative helicity: 41 m²/s²
0-3 km storm-relative helicity: 69 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.2

Open this sounding in Storm Lab

The text

As transmitted.

960 
WGUS51 KPHI 061032
FFWPHI
PAC029-091-061445-
/O.NEW.KPHI.FF.W.0017.220906T1032Z-220906T1445Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Mount Holly NJ
632 AM EDT Tue Sep 6 2022

The National Weather Service in Mount Holly has issued a

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

* Until 1045 AM EDT.

* At 632 AM EDT, Doppler radar and automated rain gauges indicated 
  thunderstorms producing heavy rain across the warned area. Between 
  2.5 and 3.5 inches of rain have fallen. The expected rainfall rate 
  is 1 to 2 inches in 1 hour. Additional rainfall amounts of 1 to 2 
  inches are possible in the warned area. Flash flooding is ongoing 
  or expected to begin shortly.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Radar and automated gauges.

  IMPACT...Flooding of small creeks and streams, urban areas,
           highways, streets, and underpasses as well as other
           drainage and low lying areas.

* Some locations that may experience flash flooding include...
  West Chester, Norristown, Phoenixville, Lansdale, West Norriton, 
  East Norriton, Coatesville, Westtown, Downingtown, Souderton, 
  Collegeville, and Royersford.

This includes the following highways...
	Pennsylvania Turnpike between mile markers 308 and 330.
	Interstate 76 in Pennsylvania between mile markers 327 and 329.
	Northeast Extension between mile markers 23 and 38.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4034 7550 4039 7543 4026 7521 4007 7536
      4004 7541 4003 7541 3990 7557 3987 7576
      3991 7586 4014 7571

FLASH FLOOD...RADAR AND GAUGE INDICATED
EXPECTED RAINFALL RATE...1-2 INCHES IN 1 HOUR

$$

Staarmann

1 follow-up statement

560 
WGUS71 KPHI 061437
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
1037 AM EDT Tue Sep 6 2022

PAC029-091-061447-
/O.EXP.KPHI.FF.W.0017.000000T0000Z-220906T1445Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Chester PA-Montgomery PA-
1037 AM EDT Tue Sep 6 2022

...FLASH FLOOD WARNING WILL EXPIRE AT 1045 AM EDT THIS MORNING FOR 
NORTHEASTERN CHESTER AND CENTRAL MONTGOMERY COUNTIES...

The heavy rain has ended. Flooding is no longer expected to pose a 
threat.

A Flood Watch remains in effect until 800 PM EDT.


LAT...LON 4034 7550 4039 7543 4026 7521 4007 7536
      4004 7541 4003 7541 3990 7557 3987 7576
      3991 7586 4014 7571

$$

Iovino

The office that day

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

Issued	Product	Office	Counties	Lasted
Sep 6, 5:11 AM EDT	Areal Flood Advisory	PHI	Berks, Chester, Delaware, Montgomery	4 hr
Sep 6, 6:55 AM EDT	Flash Flood Warning	PHI	Chester, Delaware, Montgomery, Philadelphia	4 hr
Sep 6, 6:58 AM EDT	Areal Flood Advisory	PHI	Berks	116 min
Sep 6, 7:00 AM EDT	Areal Flood Advisory	PHI	Lehigh, Northampton	114 min
Sep 6, 7:15 AM EDT	Areal Flood Advisory	PHI	Bucks	3 hr
Sep 6, 7:50 AM EDT	Areal Flood Advisory	PHI	Delaware, Philadelphia	4 hr
Sep 6, 8:07 AM EDT	River Flood Warning	PHI	Chester	4 hr

Nearby

Flash Flood Warnings in Pennsylvania, 2022 Every flash flood warning in 2022

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.