Alert archive / Pennsylvania / Flash Flood Warnings in 2021

Flash Flood Warning 39, NWS Philadelphia/Mount Holly

August 18, 2021Berks County, Pennsylvania

NWS Philadelphia/Mount Holly issued this flash flood warning at Aug 18, 2021, 9:30 PM EDT for Berks County, Pennsylvania. It was in force for 2 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 18, 2021, 9:30 PM EDT (01:30 UTC)
Expired: Aug 18, 2021, 11:56 PM EDT
In force: 2 hr
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Flood severity: None

County Berks County, PA

The radar

The Philadelphia radar (KDIX), 143 km from the middle of the area, began a volume at 01:29 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 00:00Z, 1.5 hours before the alert went out and 189 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: 1288 J/kg
Mixed-layer CIN: -8 J/kg
Mixed-layer LCL: 1100 m above ground
0-6 km bulk shear: 30 kt
0-1 km storm-relative helicity: 126 m²/s²
0-3 km storm-relative helicity: 171 m²/s²
Significant tornado parameter: 0.6
Supercell composite: 5.9

Open this sounding in Storm Lab

The text

As transmitted.

998 
WGUS51 KPHI 190130
FFWPHI
PAC011-190530-
/O.NEW.KPHI.FF.W.0039.210819T0130Z-210819T0530Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Mount Holly NJ
930 PM EDT Wed Aug 18 2021

The National Weather Service in Mount Holly has issued a

* Flash Flood Warning for...
  South Central Berks County in eastern Pennsylvania...

* Until 130 AM EDT.

* At 930 PM EDT, Doppler radar and automated rain gauges indicated 
  thunderstorms producing heavy rain across the warned area. Between 
  1 and 2 inches of rain have fallen. Additional rainfall amounts of 
  1 to 1.5 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 will experience flash flooding include...
  Reading, Wyomissing, Sinking Spring, Laureldale, Wernersville, 
  Spring Ridge, Shillington, West Reading, Mount Penn, Mohnton, 
  Kenhorst, and St. Lawrence.

This includes the following highways...
	Interstate 176 in Pennsylvania between mile markers 8 and 11.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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

&&

LAT...LON 4031 7614 4040 7592 4034 7580 4021 7599
      4022 7599 4025 7604 4027 7608 4028 7609
      4029 7611 4029 7612

FLASH FLOOD...RADAR AND GAUGE INDICATED

$$

JEO

2 follow-up statements

538 
WGUS71 KPHI 190219
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
1019 PM EDT Wed Aug 18 2021

PAC011-190530-
/O.CON.KPHI.FF.W.0039.000000T0000Z-210819T0530Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Berks PA-
1019 PM EDT Wed Aug 18 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 130 AM EDT THURSDAY 
FOR SOUTH CENTRAL BERKS COUNTY...

At 1019 PM EDT, Doppler radar and automated rain gauges indicated 
thunderstorms producing heavy rain across the warned area. Between 2 
and 3 inches of rain have fallen. Additional rainfall amounts up to 
0.5 inches are possible in the warned area. The heaviest rain has 
ended, but runoff will continue and lead to a continued threat of 
flash flooding. 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 will experience flash flooding include...
  Reading, Wyomissing, Sinking Spring, Laureldale, Wernersville, 
  Spring Ridge, Shillington, West Reading, Mount Penn, Mohnton, 
  Kenhorst, and St. Lawrence.

This includes the following highways...
	Interstate 176 in Pennsylvania between mile markers 9 and 11.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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

&&

LAT...LON 4031 7614 4040 7592 4034 7580 4021 7599
      4022 7599 4025 7604 4027 7608 4028 7609
      4029 7611 4029 7612

FLASH FLOOD...RADAR AND GAUGE INDICATED

$$

JEO

683 
WGUS71 KPHI 190356
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
1156 PM EDT Wed Aug 18 2021

PAC011-190406-
/O.CAN.KPHI.FF.W.0039.000000T0000Z-210819T0530Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Berks PA-
1156 PM EDT Wed Aug 18 2021

...FLASH FLOOD WARNING IS CANCELLED FOR SOUTH CENTRAL BERKS COUNTY...

Flood waters have receded. The heavy rain has ended. Flooding is no 
longer expected to pose a threat. Please continue to heed remaining 
road closures.

A Flash Flood Watch remains in effect until 800 AM EDT Thursday for 
portions of east central Pennsylvania...and northeast Pennsylvania.

LAT...LON 4031 7614 4040 7592 4034 7580 4021 7599
      4022 7599 4025 7604 4027 7608 4028 7609
      4029 7611 4029 7612

$$

JEO

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 18, 8:53 PM EDT	Areal Flood Advisory	PHI	Berks	3 hr
Aug 18, 9:10 PM EDT	Areal Flood Advisory	PHI	Lehigh, Monroe, Northampton	3 hr
Aug 18, 9:35 PM EDT	Areal Flood Advisory	PHI	Berks, Lehigh	3 hr
Aug 18, 9:45 PM EDT	Areal Flood Advisory	PHI	Berks	3 hr
Aug 18, 9:47 PM EDT	Special Weather Statement	PHI	Berks	58 min
Aug 18, 10:16 PM EDT	Flash Flood Warning	PHI	Berks, Lehigh	3 hr
Aug 18, 10:44 PM EDT	Flash Flood Warning	PHI	Lehigh, Monroe, Northampton	4 hr
Aug 18, 10:50 PM EDT	Flash Flood Warning	PHI	Bucks, Chester, Montgomery	4 hr
Aug 18, 11:19 PM EDT	Areal Flood Advisory	PHI	Bucks, Lehigh, Northampton	3 hr
Aug 18, 11:19 PM EDT	Special Weather Statement	PHI	Bucks, Chester, Montgomery	41 min
Aug 18, 11:47 PM EDT	Flash Flood Warning	PHI	Chester	2 hr
Aug 19, 12:04 AM EDT	Special Weather Statement	PHI	Bucks, Delaware, Montgomery	71 min
Aug 19, 12:26 AM EDT	Tornado Warning	PHI	Bucks, Montgomery	34 min
Aug 19, 12:31 AM EDT	Flash Flood Warning	PHI	Bucks, Chester, Delaware, Montgomery	4 hr
Aug 19, 12:44 AM EDT	River Flood Warning	PHI	Chester	5 hr
Aug 19, 12:47 AM EDT	Tornado Warning	PHI	Chester, Delaware, Montgomery, Philadelphia	28 min
Aug 19, 12:48 AM EDT	Tornado Warning	PHI	Bucks	27 min
Aug 19, 1:14 AM EDT	Special Weather Statement	PHI	Bucks, Delaware, Philadelphia	91 min
Aug 19, 1:30 AM EDT	Flash Flood Warning	PHI	Bucks, Delaware, Montgomery, Philadelphia	4 hr
Aug 19, 2:05 AM EDT	Areal Flood Advisory	PHI	Bucks	3 hr
Aug 19, 2:13 AM EDT	Flash Flood Warning	PHI	Bucks, Philadelphia	4 hr
Aug 19, 4:33 AM EDT	Areal Flood Warning	PHI	Chester, Delaware	4 hr
Aug 19, 6:09 AM EDT	Areal Flood Warning	PHI	Bucks, Philadelphia	3 hr
Aug 19, 8:50 AM EDT	Areal Flood Warning	PHI	Montgomery, Philadelphia	3 hr
Aug 19, 10:40 AM EDT	Areal Flood Warning	PHI	Delaware	3 hr

Nearby

Flash Flood Warnings in Pennsylvania, 2021 Every flash flood warning in 2021

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.