Alert archive / Pennsylvania / Mesoscale Discussions in 2004

Mesoscale Discussion 1495

July 4, 20044 states

The Storm Prediction Center issued this mesoscale discussion at Jul 4, 2004, 11:08 AM EDT for 4 states. It was in force for 3 hr.

The area

The outline as issued.

The facts

Issued: Jul 4, 2004, 11:08 AM EDT (15:08 UTC)
Expired: Jul 4, 2004, 1:45 PM EDT
In force: 3 hr
Issued by: the Storm Prediction Center

All 57 counties

Allegany County, NY, Cattaraugus County, NY, Chautauqua County, NY, Erie County, NY, Genesee County, NY, Wyoming County, NY, Ashtabula County, OH, Belmont County, OH, Carroll County, OH, Columbiana County, OH, Guernsey County, OH, Harrison County, OH, Jefferson County, OH, Mahoning County, OH, Meigs County, OH, Monroe County, OH, Noble County, OH, Trumbull County, OH, Washington County, OH, Allegheny County, PA, Armstrong County, PA, Beaver County, PA, Butler County, PA, Cambria County, PA, Cameron County, PA, Clarion County, PA, Clearfield 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, Venango County, PA, Warren County, PA, Washington County, PA, Westmoreland County, PA, Brooke County, WV, Doddridge County, WV, Hancock County, WV, Jackson County, WV, Marion County, WV, Marshall County, WV, Mason County, WV, Monongalia County, WV, Ohio County, WV, Pleasants County, WV, Ritchie County, WV, Tyler County, WV, Wetzel County, WV, Wirt County, WV, Wood County, WV

The radar

The Pittsburgh radar (KPBZ), 74 km from the middle of the area, began a volume at 15:07 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.

Severe Thunderstorm Watch 549Jul 4, 12:50 PM EDT

The nearest sounding before it

Buffalo Intl Airport, NY (KBUF), launched 12:00Z, 3.1 hours before the alert went out and 221 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: 509 J/kg
Mixed-layer CIN: -73 J/kg
Mixed-layer LCL: 1039 m above ground
0-6 km bulk shear: 30 kt
0-1 km storm-relative helicity: 102 m²/s²
0-3 km storm-relative helicity: 104 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.7

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
Jul 4, 3:00 PM EDT	Mesoscale Discussion	SPC	Allegany, Cattaraugus, Chautauqua, Erie, Genesee, Wyoming	2 hr
Jul 4, 3:55 PM EDT	Severe Thunderstorm Watch	SPC	Allegany, Cattaraugus, Cayuga, Chautauqua, Chemung, Erie and 12 more	6 hr
Jul 4, 7:29 PM EDT	Mesoscale Discussion	SPC	Allegany, Genesee, Livingston, Monroe, Ontario, Orleans and 3 more	61 min
Jul 4, 12:50 PM EDT	Severe Thunderstorm Watch	SPC	Ashtabula, Athens, Belmont, Carroll, Columbiana, Coshocton and 23 more	5 hr
Jul 4, 4:55 PM EDT	Mesoscale Discussion	SPC	Bedford, Blair, Cambria, Cameron, Clearfield, Elk and 9 more	65 min

Nearby

Mesoscale Discussions in Pennsylvania, 2004 Mesoscale Discussions in West Virginia, 2004 Mesoscale Discussions in Ohio, 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.