Alert archive / Pennsylvania / Mesoscale Discussions in 2004

Mesoscale Discussion 737

May 18, 20044 states

The Storm Prediction Center issued this mesoscale discussion at May 18, 2004, 12:54 PM EDT for 4 states. It was in force for 66 min.

The area

The outline as issued.

The facts

Issued: May 18, 2004, 12:54 PM EDT (16:54 UTC)
Expired: May 18, 2004, 2:00 PM EDT
In force: 66 min
Issued by: the Storm Prediction Center

All 52 counties

Cattaraugus County, NY, Belmont County, OH, Carroll County, OH, Columbiana County, OH, Coshocton County, OH, Guernsey County, OH, Harrison County, OH, Holmes County, OH, Jefferson County, OH, Knox County, OH, Mahoning County, OH, Monroe County, OH, Morgan County, OH, Muskingum County, OH, Noble County, OH, Portage County, OH, Stark County, OH, Trumbull County, OH, Tuscarawas County, OH, Wayne County, OH, Allegheny County, PA, Armstrong County, PA, Beaver County, PA, Blair County, PA, Butler County, PA, Cambria County, PA, Cameron County, PA, Centre County, PA, Clarion County, PA, Clearfield County, PA, Crawford County, PA, Elk County, PA, Fayette County, PA, Forest County, PA, Greene County, PA, Huntingdon County, PA, Indiana County, PA, Jefferson County, PA, Juniata County, PA, Lawrence County, PA, McKean County, PA, Mercer County, PA, Mifflin County, PA, Potter County, PA, Venango County, PA, Warren County, PA, Washington County, PA, Westmoreland County, PA, Brooke County, WV, Hancock County, WV, Marshall County, WV, Ohio County, WV

The radar

The Pittsburgh radar (KPBZ), 15 km from the middle of the area, began a volume at 16:54 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 (KPIT), launched 12:00Z, 4.9 hours before the alert went out and 26 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: 312 J/kg
Mixed-layer CIN: -25 J/kg
Mixed-layer LCL: 635 m above ground
0-6 km bulk shear: 36 kt
0-1 km storm-relative helicity: 254 m²/s²
0-3 km storm-relative helicity: 254 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 1.8

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
May 18, 1:04 PM EDT	Mesoscale Discussion	SPC	Albany, Broome, Cayuga, Chemung, Chenango, Clinton and 28 more	56 min
May 18, 1:50 PM EDT	Severe Thunderstorm Watch	SPC	Albany, Allegany, Broome, Cattaraugus, Cayuga, Chemung and 39 more	8 hr
May 18, 2:54 PM EDT	Mesoscale Discussion	SPC	Bronx, Dutchess, Kings, New York, Orange, Putnam and 3 more	96 min
May 18, 4:38 PM EDT	Mesoscale Discussion	SPC	Albany, Chenango, Cortland, Fulton, Greene, Madison and 7 more	2 hr
May 18, 6:24 PM EDT	Mesoscale Discussion	SPC	Albany, Broome, Cayuga, Chemung, Chenango, Columbia and 22 more	2 hr
May 18, 12:55 PM EDT	Mesoscale Discussion	SPC	Allen, Auglaize, Darke, Logan, Mercer, Miami and 5 more	2 hr
May 18, 1:45 PM EDT	Severe Thunderstorm Watch	SPC	Allen, Ashland, Athens, Auglaize, Belmont, Butler and 66 more	6 hr
May 18, 4:02 PM EDT	Mesoscale Discussion	SPC	Allen, Auglaize, Belmont, Champaign, Clark, Coshocton and 31 more	118 min
May 18, 7:09 PM EDT	Mesoscale Discussion	SPC	Athens, Auglaize, Belmont, Brown, Butler, Carroll and 43 more	96 min
May 18, 7:49 PM EDT	Mesoscale Discussion	SPC	Chester, Delaware, Lancaster, Montgomery, Philadelphia, York	2 hr
May 18, 1:14 PM EDT	Mesoscale Discussion	SPC	Berkeley, Hampshire, Hardy, Jefferson, Pendleton	2 hr

Nearby

Mesoscale Discussions in Pennsylvania, 2004 Mesoscale Discussions in Ohio, 2004 Mesoscale Discussions in West Virginia, 2004 Every mesoscale discussion in 2004

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.