Alert archive / Pennsylvania / Mesoscale Discussions in 2011

Mesoscale Discussion 694

May 3, 20114 states

The Storm Prediction Center issued this mesoscale discussion at May 3, 2011, 6:51 PM EDT for 4 states. It was in force for 84 min.

The area

The outline as issued.

The facts

Issued: May 3, 2011, 6:51 PM EDT (22:51 UTC)
Expired: May 3, 2011, 8:15 PM EDT
In force: 84 min
Issued by: the Storm Prediction Center

All 46 counties

Allegany County, MD, Washington County, MD, Adams County, PA, Bedford County, PA, Berks County, PA, Bradford County, PA, Carbon County, PA, Centre County, PA, Clinton County, PA, Columbia County, PA, Cumberland County, PA, Dauphin County, PA, Franklin County, PA, Fulton County, PA, Huntingdon County, PA, Juniata County, PA, Lackawanna County, PA, Lancaster County, PA, Lebanon County, PA, Lehigh County, PA, Luzerne County, PA, Lycoming County, PA, Mifflin County, PA, Monroe County, PA, Montour County, PA, Northampton County, PA, Northumberland County, PA, Perry County, PA, Pike County, PA, Schuylkill County, PA, Snyder County, PA, Sullivan County, PA, Susquehanna County, PA, Tioga County, PA, Union County, PA, Wayne County, PA, Wyoming County, PA, York County, PA, City of Winchester, VA, Clarke County, VA, Frederick County, VA, Berkeley County, WV, Hampshire County, WV, Jefferson County, WV, Mineral County, WV, Morgan County, WV

The radar

The State College radar (KCCX), 102 km from the middle of the area, began a volume at 22:52 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

Phillips Aaf/Abe, MD (KAPG), launched 12:00Z, 10.9 hours before the alert went out and 136 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 1037 m above ground
0-6 km bulk shear: 43 kt
0-1 km storm-relative helicity: 137 m²/s²
0-3 km storm-relative helicity: 192 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.

541 
ACUS11 KWNS 032251
SWOMCD
SPC MCD 032251 
NYZ000-NJZ000-PAZ000-MDZ000-VAZ000-WVZ000-040015-

MESOSCALE DISCUSSION 0694
NWS STORM PREDICTION CENTER NORMAN OK
0551 PM CDT TUE MAY 03 2011

AREAS AFFECTED...CNTRL AND ERN PA...ERN WV...NRN VA...WRN MD

CONCERNING...SEVERE THUNDERSTORM WATCH 263...

VALID 032251Z - 040015Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 263
CONTINUES.

A WIND DAMAGE THREAT WILL EXIST WITH A LINE OF THUNDERSTORMS MOVING
THROUGH ERN PA FOR SEVERE MORE HOURS. THE SEVERE THREAT SHOULD BE
CONTAINED BY WW 263 AND WW ISSUANCE BEYOND THE 02Z EXPIRATION IS NOT
ANTICIPATED.

A LINE OF STRONG TO SEVERE THUNDERSTORMS IS ONGOING ACROSS ECNTRL PA
ALONG THE WRN EDGE OF AN AXIS OF INSTABILITY. MESOANALYSIS CURRENTLY
SHOWS SBCAPE VALUES RANGING FROM 500 TO 1000 J/KG EXTENDING NNEWD
ACROSS MD AND MOST OF ERN PA. THE LINE IS ALSO LOCATED ON THE SERN
EDGE OF STRONGER MID-LEVEL FLOW WHERE 0-6 KM SHEAR VALUES ARE
ESTIMATED IN THE 45 TO 55 KT RANGE. THIS ENVIRONMENT ALONG WITH
STEEP LOW-LEVEL LAPSE RATES SHOULD BE ENOUGH FOR A WIND DAMAGE
THREAT FOR THE NEXT FEW HOURS AS THE LINE MOVES INTO FAR ERN PA.
INSTABILITY IS EXPECTED TO GRADUALLY WEAKEN THIS EVENING ACROSS ERN
PA WHICH SHOULD RESULT IN A GRADUAL DECREASE IN THE SEVERE WEATHER
THREAT ESPECIALLY AS THE 02Z WATCH EXPIRATION APPROACHES.

..BROYLES.. 05/03/2011

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

ATTN...WFO...OKX...PHI...BGM...CTP...LWX...PBZ...

LAT...LON   39087828 39357915 39717893 39707880 40037877 40297864
            40237824 40477819 40687814 40737835 40997807 41227806
            41477793 41467762 41967758 41987530 41797509 41537498
            41417474 41337471 41167492 40967510 40857504 40737520
            40627521 40427546 40437551 40187572 40107590 39767606
            39757739 39367769 39057790 39087828

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 3, 2:27 PM EDT	Mesoscale Discussion	SPC	Baltimore, Carroll, Frederick, Washington	2 hr
May 3, 3:47 PM EDT	Severe Thunderstorm Watch	SPC	Allegany, Washington	6 hr
May 3, 7:22 PM EDT	Mesoscale Discussion	SPC	Carroll, Floyd, Franklin, Henry, Patrick, Pittsylvania and 3 more	83 min

Nearby

Mesoscale Discussions in Pennsylvania, 2011 Mesoscale Discussions in West Virginia, 2011 Mesoscale Discussions in 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.