Alert archive / Pennsylvania / Mesoscale Discussions in 2015

Mesoscale Discussion 987

June 12, 20154 states

The Storm Prediction Center issued this mesoscale discussion at Jun 12, 2015, 2:03 PM EDT for 4 states. It was in force for 87 min.

The area

The outline as issued.

The facts

Issued: Jun 12, 2015, 2:03 PM EDT (18:03 UTC)
Expired: Jun 12, 2015, 3:30 PM EDT
In force: 87 min
Issued by: the Storm Prediction Center
Chance of a watch: 20%

All 43 counties

Baltimore County, MD, Carroll County, MD, Frederick County, MD, Howard County, MD, Montgomery County, MD, Washington County, MD, Adams County, PA, Carbon County, PA, Columbia County, PA, Cumberland County, PA, Dauphin County, PA, Franklin County, PA, Juniata County, PA, Lancaster County, PA, Lebanon County, PA, Luzerne County, PA, Lycoming County, PA, Mifflin County, PA, Montour County, PA, Northumberland County, PA, Perry County, PA, Schuylkill County, PA, Snyder County, PA, Sullivan County, PA, Union County, PA, York County, PA, Arlington County, VA, City of Fairfax, VA, City of Falls Church, VA, City of Manassas, VA, City of Manassas Park, VA, City of Winchester, VA, Clarke County, VA, Fairfax County, VA, Fauquier County, VA, Frederick County, VA, Loudoun County, VA, Prince William County, VA, Rappahannock County, VA, Warren County, VA, Berkeley County, WV, Jefferson County, WV, Morgan County, WV

The radar

The State College radar (KCCX), 111 km from the middle of the area, began a volume at 18:06 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, 6.1 hours before the alert went out and 138 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: 325 J/kg
Mixed-layer CIN: -121 J/kg
Mixed-layer LCL: 1369 m above ground
0-6 km bulk shear: 22 kt
0-1 km storm-relative helicity: 38 m²/s²
0-3 km storm-relative helicity: 67 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.1

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.

Issued	Product	Office	Counties	Lasted
Jun 12, 1:14 PM EDT	Severe Thunderstorm Watch	SPC	Garrett	8 hr
Jun 12, 6:53 PM EDT	Mesoscale Discussion	SPC	Garrett	97 min
Jun 12, 12:52 PM EDT	Mesoscale Discussion	SPC	Beaver, Crawford, Lawrence, Mercer	113 min
Jun 12, 2:54 PM EDT	Severe Thunderstorm Watch	SPC	McKean, Potter, Tioga, Warren	6 hr
Jun 12, 4:21 PM EDT	Mesoscale Discussion	SPC	Allegheny, Armstrong, Beaver, Butler, Clarion, Clearfield and 7 more	84 min
Jun 12, 7:25 PM EDT	Severe Thunderstorm Watch	SPC	Bedford, Blair, Bradford, Cambria, Centre, Columbia and 17 more	4 hr

Nearby

Mesoscale Discussions in Pennsylvania, 2015 Mesoscale Discussions in Virginia, 2015 Mesoscale Discussions in Maryland, 2015 Every 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.