Alert archive / Pennsylvania / Flash Flood Warnings in 2021

Flash Flood Warning 19, NWS State College, PA

August 18, 2021Lancaster County, Pennsylvania

NWS State College, PA issued this flash flood warning at Aug 18, 2021, 9:11 PM EDT for Lancaster County, Pennsylvania. It was in force for 108 min. 2 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: Aug 18, 2021, 9:11 PM EDT (01:11 UTC)
Expired: Aug 18, 2021, 10:59 PM EDT
In force: 108 min
Issued by: NWS State College, PA
Area: Storm-based polygon
Damage threat: Considerable
Flood severity: None

County Lancaster County, PA

The radar

The Philadelphia radar (KDIX), 150 km from the middle of the area, began a volume at 01:14 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
Aug 18, 9:25 PM EDT	FLASH FLOOD	1 Sw Lancaster, PA	WATER RESCUE IN LANCASTER CITY.
Aug 18, 9:43 PM EDT	FLASH FLOOD	1 W Lancaster, PA	NUMEROUS ROADWAYS FLOODED IN LANCASTER CITY.

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, 1.2 hours before the alert went out and 168 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.

591 
WGUS51 KCTP 190111
FFWCTP
PAC071-190415-
/O.NEW.KCTP.FF.W.0019.210819T0111Z-210819T0415Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service State College PA
911 PM EDT Wed Aug 18 2021

The National Weather Service in State College has issued a

* Flash Flood Warning for...
  Northeastern Lancaster County in south central Pennsylvania...

* Until 1215 AM EDT.

* At 911 PM EDT, Doppler radar indicated heavy rain across the 
  warned area. Up to 2 inches of rain have fallen. Additional 
  rainfall amounts up to 2 inches are possible in the warned area. 
  Flash flooding is ongoing or expected to begin shortly.

  HAZARD...Life threatening flash flooding. Heavy rain producing
           flash flooding.

  SOURCE...Radar.

  IMPACT...Life threatening flash flooding of creeks and streams,
           urban areas, highways, streets and underpasses.

* Some locations that will experience flash flooding include...
  Lancaster, Ephrata, Lititz, Millersville, Willow Street, New 
  Holland, East Petersburg, Akron, Leola, Paradise, Denver, 
  Reamstown, Rothsville, Strasburg, Gap, Adamstown, Brickerville, 
  Terre Hill, Churchtown and Bareville.

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 4019 7637 4021 7628 4030 7613 4014 7587
      4011 7594 4004 7593 3999 7597 3987 7636
      4018 7633

FLASH FLOOD...RADAR INDICATED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE

$$

CR

1 follow-up statement

529 
WGUS71 KCTP 190259
FFSCTP

Flash Flood Statement
National Weather Service State College PA
1059 PM EDT Wed Aug 18 2021

PAC071-190309-
/O.CAN.KCTP.FF.W.0019.000000T0000Z-210819T0415Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Lancaster PA-
1059 PM EDT Wed Aug 18 2021

...FLASH FLOOD WARNING FOR NORTHEASTERN LANCASTER COUNTY HAS BEEN 
REPLACED WITH A FLOOD WARNING...

LAT...LON 4019 7622 4020 7606 4014 7588 4011 7594
      4008 7594 4006 7594 4005 7594 4004 7593
      4004 7594 4001 7596 4000 7596 3999 7597
      3987 7636 4018 7633

$$

CR

The office that day

Everything else NWS State College, PA issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 18, 8:08 PM EDT	Severe Thunderstorm Warning	CTP	Lancaster, Lebanon	37 min
Aug 18, 8:27 PM EDT	Areal Flood Advisory	CTP	Lancaster, Lebanon	3 hr
Aug 18, 8:45 PM EDT	Special Weather Statement	CTP	Lancaster	45 min
Aug 18, 8:48 PM EDT	Areal Flood Advisory	CTP	Tioga	76 min
Aug 18, 9:12 PM EDT	Severe Thunderstorm Warning	CTP	York	33 min
Aug 18, 9:21 PM EDT	Severe Thunderstorm Warning	CTP	Lancaster	39 min
Aug 18, 10:28 PM EDT	Severe Thunderstorm Warning	CTP	Lancaster	47 min
Aug 18, 10:34 PM EDT	Areal Flood Warning	CTP	Lancaster, York	11 min
Aug 18, 10:48 PM EDT	Areal Flood Warning	CTP	Lancaster, York	2 hr
Aug 18, 10:53 PM EDT	Areal Flood Advisory	CTP	Lancaster, York	3 hr
Aug 18, 10:59 PM EDT	Areal Flood Warning	CTP	Lancaster	2 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.