Alert archive / Pennsylvania / Mesoscale Discussions in 2011

Mesoscale Discussion 643

April 27, 20114 counties in New York; 15 counties in Pennsylvania

The Storm Prediction Center issued this mesoscale discussion at Apr 27, 2011, 9:03 PM EDT for 4 counties in New York; 15 counties in Pennsylvania. It was in force for 57 min.

The area

The outline as issued.

The facts

Issued: Apr 27, 2011, 9:03 PM EDT (01:03 UTC)
Expired: Apr 27, 2011, 10:00 PM EDT
In force: 57 min
Issued by: the Storm Prediction Center

Counties Cayuga County, NY, Chemung County, NY, Tioga County, NY, Tompkins County, NY, Adams County, PA, Bradford County, PA, Columbia County, PA, Cumberland County, PA, Dauphin County, PA, Juniata County, PA, Lebanon County, PA, Lycoming County, PA, Montour County, PA, Northumberland County, PA, Perry County, PA, Snyder County, PA, Sullivan County, PA, Union County, PA, York County, PA

The radar

The State College radar (KCCX), 108 km from the middle of the area, began a volume at 01:06 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 246Apr 27, 11:45 PM EDT

The nearest sounding before it

Buffalo Intl Airport, NY (KBUF), launched 00:00Z, 1.1 hours before the alert went out and 245 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: 999 m above ground
0-6 km bulk shear: 40 kt
0-1 km storm-relative helicity: 107 m²/s²
0-3 km storm-relative helicity: 80 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.1

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

232 
ACUS11 KWNS 280103
SWOMCD
SPC MCD 280103 
NYZ000-PAZ000-MDZ000-280200-

MESOSCALE DISCUSSION 0643
NWS STORM PREDICTION CENTER NORMAN OK
0803 PM CDT WED APR 27 2011

AREAS AFFECTED...WRN NY...CNTRL PA

CONCERNING...TORNADO WATCH 236...

VALID 280103Z - 280200Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 236 CONTINUES.

TORNADO WATCH 236 IS SCHEDULED TO EXPIRE AT 02Z. HOWEVER...ONGOING
TSTM ACTIVITY ALONG THE ERN PERIPHERY OF THE WW AND LEFT-SPLITS
MOVING N/NEWD FROM CNTRL MD MAY NECESSITATE A WFO TEMPORAL EXTENSION
OF THE WW BEYOND 02Z. ALTHOUGH OVERALL RADAR TRENDS SUGGEST ACTIVITY
HAS RECENTLY PEAKED AND RECENT HRRR RUNS SUGGEST THIS TREND WILL
CONTINUE...THE 00Z IAD RAOB SAMPLED A ROBUST SUPERCELL WIND PROFILE
WHICH WILL SUPPORT AT LEAST A MARGINAL SEVERE THREAT THROUGH ABOUT
03Z.

..GRAMS.. 04/28/2011

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...PHI...BGM...BUF...CTP...LWX...

LAT...LON   39677759 40327751 42747683 43077673 43277639 42457606
            41327626 40267636 39697651 39677759

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 27, 8:15 PM EDT	Severe Thunderstorm Watch	SPC	Albany, Broome, Chenango, Clinton, Cortland, Delaware and 19 more	8 hr
Apr 27, 10:45 PM EDT	Mesoscale Discussion	SPC	Albany, Broome, Chenango, Delaware, Essex, Franklin and 15 more	60 min
Apr 28, 2:20 AM EDT	Mesoscale Discussion	SPC	Broome, Chemung, Chenango, Cortland, Delaware, Fulton and 13 more	55 min
Apr 28, 3:32 AM EDT	Mesoscale Discussion	SPC	Albany, Broome, Chenango, Delaware, Fulton, Greene and 15 more	28 min
Apr 28, 4:05 AM EDT	Severe Thunderstorm Watch	SPC	Albany, Broome, Chenango, Cortland, Delaware, Fulton and 13 more	6 hr
Apr 28, 6:21 AM EDT	Mesoscale Discussion	SPC	Albany, Chenango, Columbia, Delaware, Dutchess, Fulton and 15 more	54 min
Apr 28, 9:45 AM EDT	Severe Thunderstorm Watch	SPC	Albany, Bronx, Columbia, Dutchess, Fulton, Greene and 19 more	6 hr
Apr 28, 11:49 AM EDT	Mesoscale Discussion	SPC	Albany, Bronx, Columbia, Delaware, Dutchess, Fulton and 22 more	56 min
Apr 27, 11:50 PM EDT	Severe Thunderstorm Watch	SPC	Adams, Bedford, Blair, Cambria, Cameron, Centre and 26 more	7 hr

Nearby

Mesoscale Discussions in Pennsylvania, 2011 Mesoscale Discussions in New York, 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.