Alert archive / Pennsylvania / Mesoscale Discussions in 2017

Mesoscale Discussion 761

May 18, 201711 counties in Pennsylvania; Brooke County, Hancock County, Ohio County, West Virginia

The Storm Prediction Center issued this mesoscale discussion at May 18, 2017, 4:35 PM EDT for 11 counties in Pennsylvania; Brooke County, Hancock County, Ohio County, West Virginia. It was in force for 85 min.

The area

The outline as issued.

The facts

Issued: May 18, 2017, 4:35 PM EDT (20:35 UTC)
Expired: May 18, 2017, 6:00 PM EDT
In force: 85 min
Issued by: the Storm Prediction Center
Chance of a watch: 5%

Counties Allegheny County, PA, Armstrong County, PA, Beaver County, PA, Butler County, PA, Clarion County, PA, Fayette County, PA, Indiana County, PA, Jefferson County, PA, Lawrence County, PA, Washington County, PA, Westmoreland County, PA, Brooke County, WV, Hancock County, WV, Ohio County, WV

The radar

The Pittsburgh radar (KPBZ), 15 km from the middle of the area, began a volume at 20:36 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

Pittsburgh, PA (KAGC), launched 12:00Z, 8.6 hours before the alert went out and 17 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: 104 J/kg
Mixed-layer CIN: -269 J/kg
Mixed-layer LCL: 1581 m above ground
0-6 km bulk shear: 36 kt
0-1 km storm-relative helicity: 91 m²/s²
0-3 km storm-relative helicity: 89 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

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SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 18, 2:04 PM EDT	Mesoscale Discussion	SPC	Crawford, Elk, Erie, Forest, McKean, Potter and 3 more	116 min
May 18, 3:36 PM EDT	Severe Thunderstorm Watch	SPC	Bradford, Cameron, Elk, McKean, Potter, Susquehanna and 2 more	6 hr
May 18, 5:36 PM EDT	Mesoscale Discussion	SPC	McKean, Potter, Tioga, Warren	84 min
May 18, 7:33 PM EDT	Mesoscale Discussion	SPC	Bradford, Susquehanna	87 min

Nearby

Mesoscale Discussions in Pennsylvania, 2017 Mesoscale Discussions in West Virginia, 2017 Every mesoscale discussion in 2017

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.