Alert archive / Pennsylvania / Mesoscale Discussions in 2004

Mesoscale Discussion 742

May 18, 20046 states

The Storm Prediction Center issued this mesoscale discussion at May 18, 2004, 2:54 PM EDT for 6 states. It was in force for 96 min.

The area

The outline as issued.

The facts

Issued
May 18, 2004, 2:54 PM EDT (18:54 UTC)
Expired
May 18, 2004, 4:30 PM EDT
In force
96 min
Issued by
the Storm Prediction Center
All 74 counties

New Castle County, DE, Allegany County, MD, Carroll County, MD, Cecil County, MD, Harford County, MD, Washington County, MD, Bergen County, NJ, Burlington County, NJ, Camden County, NJ, Essex County, NJ, Gloucester County, NJ, Hudson County, NJ, Hunterdon County, NJ, Mercer County, NJ, Middlesex County, NJ, Monmouth County, NJ, Morris County, NJ, Ocean County, NJ, Passaic County, NJ, Somerset County, NJ, Sussex County, NJ, Union County, NJ, Warren County, NJ, Bronx County, NY, Dutchess County, NY, Kings County, NY, New York County, NY, Orange County, NY, Putnam County, NY, Richmond County, NY, Rockland County, NY, Westchester County, NY, Adams County, PA, Bedford County, PA, Berks County, PA, Blair County, PA, Bucks County, PA, Cambria County, PA, Carbon County, PA, Centre County, PA, Chester County, PA, Clearfield County, PA, Clinton County, PA, Columbia County, PA, Cumberland County, PA, Dauphin County, PA, Delaware County, PA, Franklin County, PA, Fulton County, PA, Huntingdon County, PA, Juniata County, PA, Lackawanna County, PA, Lancaster County, PA, Lebanon County, PA, Lehigh County, PA, Luzerne County, PA, Lycoming County, PA, Mifflin County, PA, Monroe County, PA, Montgomery County, PA, Montour County, PA, Northampton County, PA, Northumberland County, PA, Perry County, PA, Philadelphia County, PA, Pike County, PA, Schuylkill County, PA, Snyder County, PA, Somerset County, PA, Union County, PA, York County, PA, Berkeley County, WV, Mineral County, WV, Morgan County, WV

The radar

The State College radar (KCCX), 112 km from the middle of the area, began a volume at 18:56 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

Phillips Aaf/Abe, MD (KAPG), launched 12:00Z, 6.9 hours before the alert went out and 117 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, Phillips Aaf/Abe, MD at 12:00Z on 2004-05-18Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 303 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, Phillips Aaf/Abe, MD at 12:00Z on 2004-05-18The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 103 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
303 J/kg
Mixed-layer CIN
-86 J/kg
Mixed-layer LCL
937 m above ground
0-6 km bulk shear
23 kt
0-1 km storm-relative helicity
103 m²/s²
0-3 km storm-relative helicity
108 m²/s²
Significant tornado parameter
0.0
Supercell composite
1.7

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.

IssuedProductOfficeCountiesLasted
May 18, 7:49 PM EDTMesoscale DiscussionSPCKent, New Castle2 hr
May 18, 1:14 PM EDTMesoscale DiscussionSPCCalvert, Charles, Howard, Montgomery, Prince George's, Saint Mary's2 hr
May 18, 12:54 PM EDTMesoscale DiscussionSPCCattaraugus66 min
May 18, 1:04 PM EDTMesoscale DiscussionSPCAlbany, Broome, Cayuga, Chemung, Chenango, Clinton and 28 more56 min
May 18, 1:50 PM EDTSevere Thunderstorm WatchSPCAlbany, Allegany, Broome, Cattaraugus, Cayuga, Chemung and 39 more8 hr
May 18, 4:38 PM EDTMesoscale DiscussionSPCAlbany, Chenango, Cortland, Fulton, Greene, Madison and 7 more2 hr
May 18, 6:24 PM EDTMesoscale DiscussionSPCAlbany, Broome, Cayuga, Chemung, Chenango, Columbia and 22 more2 hr
May 18, 1:45 PM EDTSevere Thunderstorm WatchSPCAllegheny, Armstrong, Beaver, Butler, Clarion, Fayette and 6 more6 hr
May 18, 7:09 PM EDTMesoscale DiscussionSPCAllegheny, Armstrong, Beaver, Butler, Fayette, Greene and 3 more96 min
May 18, 4:02 PM EDTMesoscale DiscussionSPCBrooke, Ohio118 min

Nearby

Mesoscale Discussions in Pennsylvania, 2004Mesoscale Discussions in New Jersey, 2004Mesoscale Discussions in New York, 2004Every 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.