Alert archive / Pennsylvania / Mesoscale Discussions in 2011

Mesoscale Discussion 569

April 25, 201127 counties in Ohio; 40 counties in Pennsylvania; Brooke County, Hancock County, Ohio County, West Virginia

The Storm Prediction Center issued this mesoscale discussion at Apr 25, 2011, 1:52 PM EDT for 27 counties in Ohio; 40 counties in Pennsylvania; Brooke County, Hancock County, Ohio County, West Virginia. It was in force for 83 min.

The area

The outline as issued.

The facts

Issued: Apr 25, 2011, 1:52 PM EDT (17:52 UTC)
Expired: Apr 25, 2011, 3:15 PM EDT
In force: 83 min
Issued by: the Storm Prediction Center

All 70 counties

Ashland County, OH, Belmont County, OH, Carroll County, OH, Columbiana County, OH, Coshocton County, OH, Cuyahoga County, OH, Fairfield County, OH, Geauga County, OH, Guernsey County, OH, Harrison County, OH, Hocking County, OH, Holmes County, OH, Jefferson County, OH, Knox County, OH, Licking County, OH, Mahoning County, OH, Medina County, OH, Muskingum County, OH, Perry County, OH, Portage County, OH, Richland County, OH, Ross County, OH, Stark County, OH, Summit County, OH, Trumbull County, OH, Tuscarawas County, OH, Wayne County, OH, Allegheny County, PA, Armstrong County, PA, Beaver County, PA, Blair County, PA, Bradford County, PA, Butler County, PA, Cambria County, PA, Cameron County, PA, Centre County, PA, Clarion County, PA, Clearfield County, PA, Clinton County, PA, Columbia County, PA, Crawford County, PA, Dauphin County, PA, Elk County, PA, Forest County, PA, Huntingdon County, PA, Indiana County, PA, Jefferson County, PA, Juniata County, PA, Lawrence County, PA, Luzerne County, PA, Lycoming County, PA, McKean County, PA, Mercer County, PA, Mifflin County, PA, Montour County, PA, Northumberland County, PA, Perry County, PA, Potter County, PA, Schuylkill County, PA, Snyder County, PA, Sullivan County, PA, Tioga County, PA, Union County, PA, Venango County, PA, Warren County, PA, Washington County, PA, Westmoreland County, PA, Brooke County, WV, Hancock County, WV, Ohio County, WV

The radar

The Pittsburgh radar (KPBZ), 83 km from the middle of the area, began a volume at 17:53 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 watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

Severe Thunderstorm Watch 202Apr 25, 2:45 PM EDT

The nearest sounding before it

Pittsburgh, PA (KPIT), launched 12:00Z, 5.9 hours before the alert went out and 80 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: 4 J/kg
Mixed-layer CIN: -53 J/kg
Mixed-layer LCL: 698 m above ground
0-6 km bulk shear: 42 kt
0-1 km storm-relative helicity: 66 m²/s²
0-3 km storm-relative helicity: 87 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

245 
ACUS11 KWNS 251752
SWOMCD
SPC MCD 251752 
PAZ000-NYZ000-WVZ000-OHZ000-251915-

MESOSCALE DISCUSSION 0569
NWS STORM PREDICTION CENTER NORMAN OK
1252 PM CDT MON APR 25 2011

AREAS AFFECTED...ERN OH...MUCH OF PA

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY 

VALID 251752Z - 251915Z

SVR WEATHER THREAT IS EXPECTED TO INCREASE ACROSS ERN OH AND MUCH OF
PA DURING THE NEXT FEW HOURS. A WW APPEARS LIKELY.

MESOANALYSIS AT 17Z INDICATES A STATIONARY FRONT MAY BE RETREATING
SLIGHTLY NWD ACROSS ERN OH/CNTRL PA AS WEAK SURFACE LOW PRESSURE
OVER FAR ERN IND APPROACHES THE REGION. COOL/CLOUDY CONDITIONS EXIST
N OF THE FRONT...WHILE CLEAR SKIES AND STRONG SURFACE HEATING /WITH
TEMPERATURES CLIMBING THROUGH THE 70S/ IS OCCURRING S OF THE FRONT.
IN ADDITION...DEWPOINTS IN THE IMMEDIATE VICINITY OF THE BOUNDARY
RESIDE IN THE 50S TO LOW 60S. THOUGH MIDLEVEL LAPSE RATES ARE NOT
PARTICULARLY STEEP...THE STRONG BOUNDARY LAYER DESTABILIZATION WILL
AID IN BOOSTING MLCAPE VALUES TO 500-1500 J/KG BY PEAK HEATING. 

VISIBLE SATELLITE IMAGERY SHOWS CUMULUS DEEPENING AND EXPANDING
ALONG AND S OF THE FRONT DURING THE LAST HR OR SO...AND RADAR
IMAGERY AND LIGHTNING DATA SHOW ISOLATED THUNDERSTORM INITIATION HAS
TAKEN PLACE NE OF PIT. AS ADDITIONAL THUNDERSTORM DEVELOPMENT OCCURS
DURING THE REMAINDER OF THE AFTERNOON...SVR WEATHER THREAT MAY
BECOME SUFFICIENT FOR WW. VWP DATA INDICATES VERTICAL SHEAR PROFILES
ARE SUFFICIENT FOR SUPERCELL DEVELOPMENT...WHICH WILL ENHANCE THE
POTENTIAL FOR LARGE HAIL AND DAMAGING WINDS. IN ADDITION...LOW-LEVEL
SHEAR WITH 0-1 KM SRH IN EXCESS OF 100 M2 S-2 MAY FAVOR A TORNADO OR
TWO.

..GARNER.. 04/25/2011

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...PHI...BGM...BUF...CTP...PBZ...RLX...CLE...ILN...

LAT...LON   41258247 41968046 42017683 41297565 40647605 40217678
            40337865 40028067 39298316 41258247

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 25, 2:47 PM EDT	Severe Thunderstorm Watch	SPC	Belmont, Carroll, Columbiana, Coshocton, Guernsey, Harrison and 12 more	7 hr
Apr 25, 6:00 PM EDT	Mesoscale Discussion	SPC	Belmont, Carroll, Columbiana, Coshocton, Guernsey, Harrison and 13 more	60 min
Apr 24, 9:02 PM EDT	Mesoscale Discussion	SPC	Barbour, Braxton, Grant, Hampshire, Hardy, Jefferson and 7 more	58 min

Nearby

Mesoscale Discussions in Pennsylvania, 2011 Mesoscale Discussions in Ohio, 2011 Mesoscale Discussions in West Virginia, 2011 Every mesoscale discussion in 2011

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.