Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 2009

Severe Thunderstorm Warning 150, NWS State College, PA

August 20, 2009Lancaster County, York County, Pennsylvania

NWS State College, PA issued this severe thunderstorm warning at Aug 20, 2009, 3:52 PM EDT for Lancaster County, York County, Pennsylvania. It was in force for 53 min. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued: Aug 20, 2009, 3:52 PM EDT (19:52 UTC)
Expired: Aug 20, 2009, 4:45 PM EDT
In force: 53 min
Issued by: NWS State College, PA
Area: Storm-based polygon

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 19:56 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, 7.9 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: 975 J/kg
Mixed-layer CIN: -94 J/kg
Mixed-layer LCL: 749 m above ground
0-6 km bulk shear: 28 kt
0-1 km storm-relative helicity: -4 m²/s²
0-3 km storm-relative helicity: 31 m²/s²
Significant tornado parameter: 0.0
Supercell composite: -0.5

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this severe thunderstorm warning 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 severe thunderstorm warning went out at Aug 20, 3:48 PM EDT, 4 minutes earlier.

Area forecast discussion, Aug 20, 3:48 PM EDT, 4 minutes before

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Hazardous weather outlook, Aug 20, 11:18 AM EDT, 4 hours 34 minutes before

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1118 AM EDT THU AUG 20 2009

PAZ004>006-010>012-017>019-024>028-033>037-041-042-045-046-049>053-
056>059-063>066-211530-
WARREN-MCKEAN-POTTER-ELK-CAMERON-NORTHERN CLINTON-CLEARFIELD-
NORTHERN CENTRE-SOUTHERN CENTRE-CAMBRIA-BLAIR-HUNTINGDON-MIFFLIN-
JUNIATA-SOMERSET-BEDFORD-FULTON-FRANKLIN-TIOGA-NORTHERN LYCOMING-
SULLIVAN-SOUTHERN CLINTON-SOUTHERN LYCOMING-UNION-SNYDER-MONTOUR-
NORTHUMBERLAND-COLUMBIA-PERRY-DAUPHIN-SCHUYLKILL-LEBANON-CUMBERLAND-
ADAMS-YORK-LANCASTER-
1118 AM EDT THU AUG 20 2009

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL PENNSYLVANIA.

.DAY ONE...THIS AFTERNOON AND TONIGHT.

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON AND
EVENING ACROSS CENTRAL PENNSYLVANIA. THE PRIMARY THREAT WILL BE
DAMAGING WIND GUSTS. LOCALLY HEAVY DOWNPOURS WILL ALSO BE
POSSIBLE.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY.

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ON FRIDAY.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

RXR

In the hours before

Special weather statement, Aug 20, 1:43 PM EDT, 2 hours 9 minutes before

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE STATE COLLEGE PA
143 PM EDT THU AUG 20 2009

PAZ057-063-065-201845-
CUMBERLAND PA-DAUPHIN PA-YORK PA-
143 PM EDT THU AUG 20 2009

...A STRONG THUNDERSTORM WILL AFFECT NORTHEASTERN
CUMBERLAND...NORTHWESTERN YORK AND SOUTH CENTRAL DAUPHIN COUNTIES
THROUGH 245 PM EDT...

AT 140 PM EDT...A STRONG THUNDERSTORM WAS LOCATED OVER LOWER ALLEN...
MOVING NORTHEAST AT 15 MPH.

WIND GUSTS TO 45 MPH AND SMALL HAIL ARE POSSIBLE WITH THIS STORM. A
15 TO 20 MINUTE PERIOD OF VERY HEAVY RAIN WILL FALL FROM THIS
STORM...AND WILL CAUSE WATER TO POND ON ROADS AND FILL POOR DRAINAGE
AREAS. THE RAIN MAY CAUSE RAPID RISES ON SOME SMALL STREAMS AND
CREEKS. ALSO EXPECT FREQUENT...DANGEROUS CLOUD TO GROUND LIGHTNING
FROM THIS STORM. DO NOT STAY IN THE OPEN NOR SEEK SHELTER UNDER
TREES WHEN LIGHTNING THREATENS...MOVE INDOORS WHEN A THUNDERSTORM
APPROACHES.

THIS STORM WILL BE NEAR LOWER ALLEN...CAMP HILL...AND ENOLA AROUND
150 PM...NEW CUMBERLAND...LEMOYNE...WORMLEYSBURG...AND WEST FAIRVIEW
AROUND 155 PM...HARRISBURG AROUND 200 PM...STEELTON AND HARRISBURG
AROUND 205 PM.

THIS WILL IMPACT THE FOLLOWING CENTRAL PENNSYLVANIA INTERSTATES...THE
PENNSYLVANIA TURNPIKE BETWEEN MILE MARKERS 232 AND 255...I-81 BETWEEN
MILE MARKERS 66 AND 76...I-83 BETWEEN MILE MARKERS 33 AND 50...I-283.

LAT...LON 4042 7676 4019 7664 4009 7699 4020 7707

EXPERIMENTAL

FORECASTER: LAMBERT

Special weather statement, Aug 20, 1:48 PM EDT, 2 hours 4 minutes before

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE STATE COLLEGE PA
148 PM EDT THU AUG 20 2009

PAZ028-050-056-057-201845-
DAUPHIN PA-JUNIATA PA-PERRY PA-SNYDER PA-
148 PM EDT THU AUG 20 2009

...STRONG THUNDERSTORMS WILL AFFECT CENTRAL JUNIATA...NORTHWESTERN
DAUPHIN...PERRY AND SOUTHEASTERN SNYDER COUNTIES THROUGH 245 PM EDT...

AT 144 PM EDT...THE LEADING EDGE OF A DEVELOPING LINE OF STRONG
THUNDERSTORMS EXTENDED FROM 16 MILES EAST OF LEWISTOWN TO 12 MILES
SOUTHEAST OF LEWISTOWN TO 12 MILES NORTHWEST OF CARLISLE...MOVING
TOWARD THE EAST NORTHEAST AT 30 MPH.

WIND GUSTS TO 45 MPH AND SMALL HAIL ARE POSSIBLE WITH THESE STORMS.
IN ADDITION A 30 MINUTE PERIOD OF VERY HEAVY RAIN WILL FALL AND COULD
CAUSE RAPID RISES ON SOME SMALL STREAMS AND CREEKS IN THE AREA.
FREQUENT...DANGEROUS CLOUD TO GROUND LIGHTNING WILL ALSO ACCOMPANY
THE THUNDERSTORMS.

THESE STORMS WILL BE NEAR LANDISBURG AROUND 200 PM...SHERMANSDALE
AROUND 210 PM...MEISERVILLE AROUND 220 PM...PORT TREVERTON AROUND 230
PM AND MILLERSBURG AROUND 240 PM.

LAT...LON 4031 7736 4029 7744 4036 7756 4042 7770
      4061 7729 4075 7686 4067 7689 4064 7694
      4062 7694 4061 7691 4037 7686 4027 7740

EXPERIMENTAL

FORECASTER: LAMBERT

Special weather statement, Aug 20, 2:06 PM EDT, 1 hour 46 minutes before

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE STATE COLLEGE PA
206 PM EDT THU AUG 20 2009

PAZ024-201915-
CAMBRIA PA-
206 PM EDT THU AUG 20 2009

...A STRONG THUNDERSTORM WILL AFFECT WESTERN CAMBRIA COUNTY...

AT 204 PM EDT...A STRONG THUNDERSTORM WAS LOCATED NEAR LIGONIER
AND MOVING TO THE NORTHEAST AT 20 MPH.

WIND GUSTS TO 40 MPH AND SMALL HAIL ARE POSSIBLE WITH THIS STORM.
EXPECT OCCASIONAL...DANGEROUS CLOUD TO GROUND LIGHTNING FROM THIS
STORM. DO NOT STAY IN THE OPEN NOR SEEK SHELTER UNDER TREES WHEN
LIGHTNING THREATENS...MOVE INDOORS WHEN A THUNDERSTORM APPROACHES.

THIS STORM WILL BE NEAR WESTMONT AROUND 250 PM...BROWNSTOWN AROUND
255 PM...EAST CONEMAUGH AROUND 300 PM...VINTONDALE AROUND 310 PM AND
NANTY-GLO AROUND 315 PM.

THIS WILL IMPACT THE FOLLOWING MAJOR ROADS...THE JOHNSTOWN
EXPRESSWAY...ROUTE 22...ROUTE 219...ROUTE 422...STATE ROAD 56.

LAT...LON 4030 7906 4037 7899 4039 7900 4059 7888
      4062 7885 4038 7872 4028 7895 4028 7906

EXPERIMENTAL

FORECASTER: LAMBERT

Special weather statement, Aug 20, 3:10 PM EDT, 42 minutes before

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE STATE COLLEGE PA
310 PM EDT THU AUG 20 2009

PAZ059-066-202000-
LANCASTER PA-LEBANON PA-
310 PM EDT THU AUG 20 2009

...A STRONG THUNDERSTORM WILL AFFECT NORTH CENTRAL LANCASTER AND
SOUTHERN LEBANON COUNTIES THROUGH 4 PM EDT...

AT 308 PM EDT...A STRONG THUNDERSTORM WAS LOCATED 4 MILES SOUTH OF
ANNVILLE...MOVING EAST AT 15 MPH.

BRIEF...WIND GUSTS TO 45 MPH AND PEA-SIZED HAIL ARE POSSIBLE WITH
THIS STORM.

THIS STORM WILL BE NEAR CORNWALL AROUND 325 PM...LEBANON AROUND 330
PM...KLEINFELTERSVILLE AROUND 355 PM AND RICHLAND AROUND 400 PM.

THIS WILL IMPACT THE PENNSYLVANIA TURNPIKE BETWEEN MILE MARKERS 261
AND 279.

THIS WILL ALSO IMPACT THE FOLLOWING MAJOR ROADS...ROUTE 322...ROUTE
422...STATE ROAD 501.

LAT...LON 4019 7654 4029 7659 4040 7628 4037 7623
      4037 7621 4027 7607

EXPERIMENTAL

FORECASTER: LAMBERT

Special weather statement, Aug 20, 3:16 PM EDT, 36 minutes before

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE STATE COLLEGE PA
316 PM EDT THU AUG 20 2009

PAZ057>059-202015-
DAUPHIN PA-LEBANON PA-SCHUYLKILL PA-
316 PM EDT THU AUG 20 2009

...STRONG THUNDERSTORMS WILL AFFECT CENTRAL DAUPHIN...NORTHWESTERN
LEBANON AND SOUTHWESTERN SCHUYLKILL COUNTIES...

AT 314 PM EDT...STRONG THUNDERSTORMS WERE ALONG A LINE FROM 4 MILES
NORTHWEST OF LINGLESTOWN TO COLONIAL PARK...MOVING NORTHEAST AT 20
MPH.

WIND GUSTS TO 45 MPH AND PEA-SIZED HAIL ARE POSSIBLE WITH THESE
STORMS.

THESE STORMS WILL BE NEAR SKYLINE VIEW AROUND 325 PM...DEHART DAM
AROUND 335 PM...PENN NATIONAL RACE AROUND 340 PM...HARPER TAVERN...
AND FORT INDIANTOWN GAP AROUND 355 PM...FORT INDIANTOWN GAP AROUND
400 PM AND JONESTOWN AROUND 405 PM.

THIS WILL IMPACT THE FOLLOWING CENTRAL PENNSYLVANIA INTERSTATES...
I-78 BETWEEN MILE MARKERS 0 AND 8...I-81 BETWEEN MILE MARKERS 71 AND
104.

THIS WILL ALSO IMPACT THE FOLLOWING MAJOR ROADS...ROUTE 22...ROUTE
209...ROUTE 322.

LAT...LON 4051 7637 4049 7642 4045 7636 4024 7677
      4038 7688 4047 7682 4046 7653 4062 7646
      4052 7630

EXPERIMENTAL

FORECASTER: DEVOIR

Special weather statement, Aug 20, 3:20 PM EDT, 32 minutes before

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE STATE COLLEGE PA
320 PM EDT THU AUG 20 2009

PAZ065-066-201945-
LANCASTER PA-YORK PA-
320 PM EDT THU AUG 20 2009

...A STRONG THUNDERSTORM WILL AFFECT CENTRAL YORK AND NORTHERN
LANCASTER COUNTIES...

AT 320 PM EDT...A STRONG THUNDERSTORM WAS LOCATED 5 MILES NORTH OF
YORK...MOVING EAST AT 25 MPH.

WIND GUSTS TO 45 MPH AND PEA-SIZED HAIL WILL BE POSSIBLE WITH THIS
STORM.

THIS STORM WILL BE NEAR YORK HAVEN AROUND 325 PM...BAINBRIDGE AROUND
330 PM...MAYTOWN AROUND 335 PM...MARIETTA AROUND 340 PM AND MOUNT JOY
AROUND 345 PM.

THIS WILL IMPACT THE FOLLOWING CENTRAL PENNSYLVANIA INTERSTATES...THE
PENNSYLVANIA TURNPIKE BETWEEN MILE MARKERS 267 AND 282...I-83 BETWEEN
MILE MARKERS 17 AND 30.

THIS WILL ALSO IMPACT THE FOLLOWING MAJOR ROADS...STATE HIGHWAY
283...ROUTE 30...ROUTE 222...ROUTE 322...STATE ROAD 501.

LAT...LON 3992 7680 4008 7690 4019 7656 4025 7641
      4025 7632 4032 7615 4009 7610

EXPERIMENTAL

FORECASTER: DEVOIR

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 19, 8:13 PM EDT	Areal Flood Advisory	CTP	Lancaster, Lebanon, York	3 hr
Aug 19, 10:12 PM EDT	Areal Flood Warning	CTP	Cumberland	108 min
Aug 20, 1:43 PM EDT	Special Weather Statement	CTP	Dauphin	62 min
Aug 20, 1:48 PM EDT	Special Weather Statement	CTP	Juniata, Perry	57 min
Aug 20, 2:06 PM EDT	Special Weather Statement	CTP	Cambria	69 min
Aug 20, 2:32 PM EDT	Areal Flood Advisory	CTP	Juniata, Perry	118 min
Aug 20, 2:40 PM EDT	Severe Thunderstorm Warning	CTP	Dauphin, Juniata, Northumberland, Perry, Snyder	50 min
Aug 20, 3:04 PM EDT	Tornado Warning	CTP	Dauphin, Northumberland, Perry	26 min
Aug 20, 3:10 PM EDT	Special Weather Statement	CTP	Lebanon	50 min
Aug 20, 3:15 PM EDT	Severe Thunderstorm Warning	CTP	Dauphin, Lebanon, Northumberland, Perry, Schuylkill	60 min
Aug 20, 3:16 PM EDT	Special Weather Statement	CTP	Dauphin	59 min
Aug 20, 3:20 PM EDT	Special Weather Statement	CTP	Lancaster	25 min
Aug 20, 4:22 PM EDT	Special Weather Statement	CTP	Lancaster	53 min
Aug 20, 4:29 PM EDT	Tornado Warning	CTP	Lancaster	31 min
Aug 20, 4:57 PM EDT	Tornado Warning	CTP	Lancaster	63 min
Aug 20, 5:15 PM EDT	Special Weather Statement	CTP	Mifflin	60 min
Aug 20, 5:17 PM EDT	Special Weather Statement	CTP	Franklin	58 min
Aug 20, 7:57 PM EDT	Special Weather Statement	CTP	McKean	33 min

Nearby

Severe Thunderstorm Warnings in Pennsylvania, 2009 Every severe thunderstorm warning 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.