Alert archive / New York / Mesoscale Discussions in 2015

Mesoscale Discussion 399

April 20, 201522 counties in New York; 14 counties in Pennsylvania

The Storm Prediction Center issued this mesoscale discussion at Apr 20, 2015, 3:23 PM EDT for 22 counties in New York; 14 counties in Pennsylvania. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Apr 20, 2015, 3:23 PM EDT (19:23 UTC)
Expired: Apr 20, 2015, 5:30 PM EDT
In force: 2 hr
Issued by: the Storm Prediction Center
Chance of a watch: 60%

All 36 counties

Allegany County, NY, Broome County, NY, Cattaraugus County, NY, Cayuga County, NY, Chemung County, NY, Cortland County, NY, Erie County, NY, Genesee County, NY, Livingston County, NY, Monroe County, NY, Niagara County, NY, Onondaga County, NY, Ontario County, NY, Orleans County, NY, Schuyler County, NY, Seneca County, NY, Steuben County, NY, Tioga County, NY, Tompkins County, NY, Wayne County, NY, Wyoming County, NY, Yates County, NY, Bradford County, PA, Cameron County, PA, Centre County, PA, Clearfield County, PA, Clinton County, PA, Elk County, PA, Jefferson County, PA, Lycoming County, PA, McKean County, PA, Potter County, PA, Sullivan County, PA, Susquehanna County, PA, Tioga County, PA, Wyoming County, PA

The radar

The State College radar (KCCX), 124 km from the middle of the area, began a volume at 19:23 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

Buffalo Intl Airport, NY (KBUF), launched 12:00Z, 7.4 hours before the alert went out and 136 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 982 m above ground
0-6 km bulk shear: 28 kt
0-1 km storm-relative helicity: 429 m²/s²
0-3 km storm-relative helicity: 437 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 20, 7:31 PM EDT	Mesoscale Discussion	SPC	Broome, Cayuga, Chemung, Chenango, Cortland, Delaware and 5 more	2 hr
Apr 20, 7:56 PM EDT	Severe Thunderstorm Watch	SPC	Broome, Cayuga, Chemung, Cortland, Schuyler, Seneca and 4 more	4 hr
Apr 20, 1:54 PM EDT	Mesoscale Discussion	SPC	Adams, Bedford, Cumberland, Franklin, Fulton, Lancaster and 1 more	3 hr
Apr 20, 3:08 PM EDT	Tornado Watch	SPC	Adams, Bedford, Berks, Blair, Bucks, Cambria and 32 more	9 hr
Apr 20, 5:01 PM EDT	Mesoscale Discussion	SPC	Adams, Bedford, Berks, Blair, Chester, Cumberland and 10 more	119 min
Apr 20, 5:57 PM EDT	Mesoscale Discussion	SPC	Bradford, Cameron, Centre, Clinton, Columbia, Luzerne and 9 more	2 hr

Nearby

Mesoscale Discussions in New York, 2015 Mesoscale Discussions in Pennsylvania, 2015 Every mesoscale discussion in 2015

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.