Alert archive / Pennsylvania / Mesoscale Discussions in 2015

Mesoscale Discussion 620

May 11, 20155 states

The Storm Prediction Center issued this mesoscale discussion at May 11, 2015, 7:26 PM EDT for 5 states. It was in force for 64 min.

The area

The outline as issued.

The facts

Issued
May 11, 2015, 7:26 PM EDT (23:26 UTC)
Expired
May 11, 2015, 8:30 PM EDT
In force
64 min
Issued by
the Storm Prediction Center
All 51 counties

Garrett County, MD, Cattaraugus County, NY, Chautauqua County, NY, Belmont County, OH, Columbiana County, OH, Harrison County, OH, Jefferson County, OH, Mahoning County, OH, Monroe County, OH, Trumbull County, OH, Allegheny County, PA, Armstrong County, PA, Beaver County, PA, Butler County, PA, Cambria County, PA, Clarion County, PA, Crawford County, PA, Elk County, PA, Erie County, PA, Fayette County, PA, Forest County, PA, Greene County, PA, Indiana County, PA, Jefferson County, PA, Lawrence County, PA, McKean County, PA, Mercer County, PA, Somerset County, PA, Venango County, PA, Warren County, PA, Washington County, PA, Westmoreland County, PA, Barbour County, WV, Braxton County, WV, Brooke County, WV, Doddridge County, WV, Gilmer County, WV, Hancock County, WV, Harrison County, WV, Lewis County, WV, Marion County, WV, Marshall County, WV, Monongalia County, WV, Ohio County, WV, Pleasants County, WV, Preston County, WV, Ritchie County, WV, Taylor County, WV, Tyler County, WV, Upshur County, WV, Wetzel County, WV

The radar

The Pittsburgh radar (KPBZ), 38 km from the middle of the area, began a volume at 23:26 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.

The nearest sounding before it

Pittsburgh, PA (KAGC), launched 12:00Z, 11.4 hours before the alert went out and 50 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-pSkew-T log-p diagram, Pittsburgh, PA at 12:00Z on 2015-05-11Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 30 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Pittsburgh, PA at 12:00Z on 2015-05-11The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 56 square meters per square second.1939Sfc1 km3 km6 km9 kmRMLM
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
30 J/kg
Mixed-layer CIN
-78 J/kg
Mixed-layer LCL
1342 m above ground
0-6 km bulk shear
23 kt
0-1 km storm-relative helicity
56 m²/s²
0-3 km storm-relative helicity
73 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.

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SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
May 11, 1:32 PM EDTMesoscale DiscussionSPCAlbany, Allegany, Broome, Cayuga, Chemung, Chenango and 29 more2 hr
May 11, 12:48 PM EDTMesoscale DiscussionSPCAllen, Auglaize, Butler, Champaign, Clark, Clermont and 36 more2 hr
May 11, 1:14 PM EDTTornado WatchSPCAllen, Ashland, Auglaize, Butler, Champaign, Clark and 43 more7 hr
May 11, 1:53 PM EDTMesoscale DiscussionSPCAdams, Athens, Brown, Gallia, Guernsey, Hocking and 12 more3 hr
May 11, 2:19 PM EDTSevere Thunderstorm WatchSPCAdams, Athens, Brown, Clermont, Clinton, Coshocton and 22 more8 hr
May 11, 2:58 PM EDTMesoscale DiscussionSPCAllen, Auglaize, Butler, Champaign, Clark, Crawford and 24 more62 min
May 11, 4:13 PM EDTMesoscale DiscussionSPCAdams, Athens, Gallia, Guernsey, Hocking, Jackson and 10 more92 min
May 11, 4:24 PM EDTMesoscale DiscussionSPCColumbiana, Geauga, Mahoning, Portage, Stark, Summit and 1 more2 hr
May 11, 4:39 PM EDTMesoscale DiscussionSPCAllen, Auglaize, Butler, Champaign, Clark, Crawford and 35 more66 min
May 11, 5:47 PM EDTSevere Thunderstorm WatchSPCAshtabula, Belmont, Carroll, Columbiana, Cuyahoga, Geauga and 12 more4 hr
May 11, 6:23 PM EDTMesoscale DiscussionSPCAdams, Brown, Clermont, Clinton, Fayette, Greene and 5 more97 min

Nearby

Mesoscale Discussions in Pennsylvania, 2015Mesoscale Discussions in West Virginia, 2015Mesoscale Discussions in Ohio, 2015Every mesoscale discussion in 2015

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.