Alert archive / Pennsylvania / Mesoscale Discussions in 2011

Mesoscale Discussion 638

April 27, 2011Carroll County, Harford County, Washington County, Maryland; 22 counties in New York; 39 counties in Pennsylvania

The Storm Prediction Center issued this mesoscale discussion at Apr 27, 2011, 6:50 PM EDT for Carroll County, Harford County, Washington County, Maryland; 22 counties in New York; 39 counties in Pennsylvania. It was in force for 55 min.

The area

The outline as issued.

The facts

Issued: Apr 27, 2011, 6:50 PM EDT (22:50 UTC)
Expired: Apr 27, 2011, 7:45 PM EDT
In force: 55 min
Issued by: the Storm Prediction Center

All 64 counties

Carroll County, MD, Harford County, MD, Washington County, MD, Allegany County, NY, Broome County, NY, Cayuga County, NY, Chemung County, NY, Chenango County, NY, Cortland County, NY, Jefferson County, NY, Lewis County, NY, Livingston County, NY, Madison County, NY, Monroe County, NY, Oneida County, NY, Onondaga County, NY, Ontario County, NY, Oswego County, NY, Schuyler County, NY, Seneca County, NY, Steuben County, NY, Tioga County, NY, Tompkins County, NY, Wayne County, NY, Yates County, NY, Adams County, PA, Berks County, PA, Blair County, PA, Bradford County, PA, Cameron County, PA, Carbon County, PA, Centre County, PA, Chester County, PA, Clinton County, PA, Columbia County, PA, Cumberland County, PA, Dauphin 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, Potter County, PA, Schuylkill County, PA, Snyder County, PA, Sullivan County, PA, Susquehanna County, PA, Tioga County, PA, Union County, PA, Wayne County, PA, Wyoming County, PA, York County, PA

The radar

The Binghamton radar (KBGM), 34 km from the middle of the area, began a volume at 22:53 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 244Apr 27, 8:15 PM EDT

The nearest sounding before it

Buffalo Intl Airport, NY (KBUF), launched 12:00Z, 10.8 hours before the alert went out and 216 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: 27 J/kg
Mixed-layer CIN: -127 J/kg
Mixed-layer LCL: 987 m above ground
0-6 km bulk shear: 56 kt
0-1 km storm-relative helicity: 118 m²/s²
0-3 km storm-relative helicity: 139 m²/s²
Significant tornado parameter: 0.0
Supercell composite: -0.0

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
Apr 27, 1:23 PM EDT	Tornado Watch	SPC	Allegany, Anne Arundel, Baltimore, Calvert, Carroll, Charles and 8 more	5 hr
Apr 27, 1:24 PM EDT	Mesoscale Discussion	SPC	Allegany, Garrett	96 min
Apr 27, 3:10 PM EDT	Tornado Watch	SPC	Garrett	7 hr
Apr 27, 3:55 PM EDT	Mesoscale Discussion	SPC	Caroline, Cecil, Dorchester, Harford, Kent, Queen Anne's and 3 more	65 min
Apr 27, 4:39 PM EDT	Mesoscale Discussion	SPC	Allegany, Anne Arundel, Baltimore, Calvert, Carroll, Charles and 10 more	66 min
Apr 27, 6:00 PM EDT	Mesoscale Discussion	SPC	Anne Arundel, Baltimore, Calvert, Carroll, Charles, Frederick and 9 more	60 min
Apr 27, 6:15 PM EDT	Tornado Watch	SPC	Allegany, Anne Arundel, Baltimore, Calvert, Carroll, Charles and 8 more	6 hr
Apr 27, 7:55 PM EDT	Mesoscale Discussion	SPC	Anne Arundel, Baltimore, Calvert, Carroll, Charles, Harford and 8 more	65 min

Nearby

Mesoscale Discussions in Pennsylvania, 2011 Mesoscale Discussions in New York, 2011 Mesoscale Discussions in Maryland, 2011 Every mesoscale discussion in 2011

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.