Alert archive / Pennsylvania / Flash Flood Watches in 2009

Flash Flood Watch 8, NWS State College, PA

August 28, 2009Lancaster County, York County, Pennsylvania

NWS State College, PA issued this flash flood watch at Aug 28, 2009, 8:17 PM EDT for Lancaster County, York County, Pennsylvania. It was in force for 7 hr.

The area

The counties it named.

The facts

Issued: Aug 28, 2009, 8:17 PM EDT (00:17 UTC)
Expired: Aug 29, 2009, 3:05 AM EDT
In force: 7 hr
Issued by: NWS State College, PA
Flood severity: None

Counties Lancaster County, PA, York County, PA

The radar

The Sterling radar (KLWX), 141 km from the middle of the area, began a volume at 00:20 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, 0.3 hours before the alert went out and 139 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: 1961 J/kg
Mixed-layer CIN: 0 J/kg
Mixed-layer LCL: 532 m above ground
0-6 km bulk shear: 24 kt
0-1 km storm-relative helicity: 47 m²/s²
0-3 km storm-relative helicity: 82 m²/s²
Significant tornado parameter: 0.5
Supercell composite: 2.4

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this flash flood watch went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS State College, PA wrote its last area forecast discussion before this flash flood watch went out at Aug 28, 8:11 PM EDT, 6 minutes earlier.

Area forecast discussion, Aug 28, 8:11 PM EDT, 6 minutes before

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Hazardous weather outlook, Aug 28, 5:28 AM EDT, 14 hours 49 minutes before

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In the hours before

Special weather statement, Aug 28, 4:52 PM EDT, 3 hours 25 minutes before

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Special weather statement, Aug 28, 5:14 PM EDT, 3 hours 3 minutes before

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Special weather statement, Aug 28, 6:33 PM EDT, 1 hour 44 minutes before

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE STATE COLLEGE PA
633 PM EDT FRI AUG 28 2009

PAZ057-059-064>066-282330-
ADAMS PA-DAUPHIN PA-LANCASTER PA-LEBANON PA-YORK PA-
633 PM EDT FRI AUG 28 2009

...A STRONG THUNDERSTORM WILL AFFECT EASTERN ADAMS...SOUTHEASTERN
DAUPHIN...SOUTHWESTERN LEBANON...WEST CENTRAL LANCASTER AND YORK
COUNTIES...

AT 627 PM EDT...A BAND OF STRONG THUNDERSTORMS WAS LOCATED FROM
8 MILES NORTH OF HANOVER...SOUTHWARD TO THE MARYLAND BORDER. THE
STORMS ARE MOVING NORTHEAST AT 25 MPH.

WIND GUSTS TO 30 MPH ARE POSSIBLE WITH THESE STORMS.

IN ADDITION...TORRENTIAL RAIN ARE LIKELY FROM THESE STORMS.
PONDING OF WATER IS LIKELY ON ROADS...AND IN AREAS OF POOR DRAINAGE.
THE RAIN WILL CAUSE RAPID RISES ON SMALL STREAMS AND CREEKS.

THE STRONGEST STORM WILL BE NEAR NEW FREEDOM AROUND 635 PM...
SHREWSBURY AROUND 640 PM...AND STEWARTSTOWN AROUND 645 PM.

THE STRONGEST STORM WILL IMPACT THE FOLLOWING CENTRAL PENNSYLVANIA
INTERSTATES...THE PENNSYLVANIA TURNPIKE BETWEEN MILE MARKERS 244 AND
266...I-83 BETWEEN MILE MARKERS 1 AND 37...I-283.

THIS WILL ALSO IMPACT THE FOLLOWING MAJOR ROADS...THE HARRISBURG
AIRPORT CONNECTOR...STATE HIGHWAY 283...ROUTE 15...ROUTE 30...AND
ROUTE 322.

LAT...LON 3994 7717 4038 7661 4018 7638 3972 7653
      3972 7720

EXPERIMENTAL

FORECASTER: MARTIN

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 28, 10:13 PM EDT	Areal Flood Advisory	CTP	Adams, York	3 hr
Aug 28, 11:23 PM EDT	Flash Flood Warning	CTP	York	3 hr
Aug 29, 4:42 PM EDT	Special Weather Statement	CTP	Montour	33 min
Aug 29, 5:03 PM EDT	Special Weather Statement	CTP	Cumberland, Dauphin, Lebanon	57 min
Aug 29, 5:13 PM EDT	Special Weather Statement	CTP	Columbia, Montour	32 min
Aug 29, 5:50 PM EDT	Special Weather Statement	CTP	Lebanon, Schuylkill	55 min

Nearby

Flash Flood Watches in Pennsylvania, 2009 Every flash flood watch in 2009

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.