Alert archive / Pennsylvania / Mesoscale Discussions in 2012

Mesoscale Discussion 1733

August 10, 20124 states

The Storm Prediction Center issued this mesoscale discussion at Aug 10, 2012, 12:49 PM EDT for 4 states. It was in force for 86 min.

The area

The outline as issued.

The facts

Issued: Aug 10, 2012, 12:49 PM EDT (16:49 UTC)
Expired: Aug 10, 2012, 2:15 PM EDT
In force: 86 min
Issued by: the Storm Prediction Center
Chance of a watch: 40%

All 47 counties

Allegany County, NY, Cattaraugus County, NY, Chautauqua County, NY, Erie County, NY, Genesee County, NY, Niagara County, NY, Orleans County, NY, Wyoming County, NY, Ashtabula County, OH, Belmont County, OH, Carroll County, OH, Columbiana County, OH, Harrison County, OH, Jefferson County, OH, Mahoning County, OH, Monroe County, OH, Portage County, OH, Trumbull County, OH, Allegheny County, PA, Armstrong County, PA, Beaver County, PA, Butler 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, Hancock County, WV, Marion County, WV, Marshall County, WV, Monongalia County, WV, Ohio County, WV, Wetzel County, WV

The radar

The Pittsburgh radar (KPBZ), 117 km from the middle of the area, began a volume at 16:49 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

Pittsburgh, PA (KAGC), launched 12:00Z, 4.8 hours before the alert went out and 129 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: 129 J/kg
Mixed-layer CIN: -29 J/kg
Mixed-layer LCL: 706 m above ground
0-6 km bulk shear: 41 kt
0-1 km storm-relative helicity: 102 m²/s²
0-3 km storm-relative helicity: 133 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.3

Open this sounding in Storm Lab

The text

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

611 
ACUS11 KWNS 101650
SWOMCD
SPC MCD 101649
NYZ000-PAZ000-MDZ000-WVZ000-OHZ000-101815-

MESOSCALE DISCUSSION 1733
NWS STORM PREDICTION CENTER NORMAN OK
1149 AM CDT FRI AUG 10 2012

AREAS AFFECTED...PARTS OF WRN NEW YORK...WRN PA

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 101649Z - 101815Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...TRENDS ARE BEING MONITORED FOR THE POSSIBILITY OF AN
INCREASING SEVERE THUNDERSTORM THREAT THAT COULD REQUIRE A WATCH
DURING THE NEXT 1-2 HOURS.

DISCUSSION...MID-LEVEL COOLING AND LIFT...GENERALLY IN THE EXIT
REGION OF THE 40-50 KT CYCLONIC 500 MB JET STREAK MIGRATING THROUGH
THE OHIO VALLEY...ARE CONTRIBUTING TO SUFFICIENT DESTABILIZATION FOR
INCREASING THUNDERSTORM ACTIVITY AHEAD OF THE SURFACE COLD FRONT
ADVANCING INTO THE UPPER OHIO VALLEY/LOWER GREAT LAKES REGION.
CONSIDERABLE CLOUD COVER IN THE WARM SECTOR OF THE LOW...NOW
CENTERED OVER SOUTHEAST LOWER MICHIGAN...HAS SLOWED BOUNDARY LAYER
HEATING...AND THIS MAY CONTINUE TO LIMIT THE SEVERE WEATHER
POTENTIAL INTO THE AFTERNOON HOURS.  HOWEVER...GIVEN THE MOISTURE
PRESENT...THERMODYNAMIC PROFILES PROBABLY WILL STILL BECOME
SUPPORTIVE OF THE RISK FOR AT LEAST MARGINALLY SEVERE
HAIL...PARTICULARLY GIVEN FAVORABLE DEEP LAYER SHEAR FOR UPDRAFT
ROTATION AND ORGANIZED CONVECTIVE DEVELOPMENT.  SEVERE WIND
GUST/TORNADO POTENTIAL REMAINS A BIT MORE UNCERTAIN...AS SOUTHERLY
LOW-LEVEL WIND FIELDS ARE EXPECTED TO REMAIN WEAK TO MODEST IN
STRENGTH AHEAD OF ACTIVITY AS IT SPREADS NORTHEASTWARD ACROSS PARTS
OF WESTERN NEW YORK/PENNSYLVANIA THROUGH 18-21Z.

..KERR/HART.. 08/10/2012

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

ATTN...WFO...BUF...CTP...PBZ...RLX...CLE...

LAT...LON   41568115 42688056 43627938 43437786 42047780 39787920
            39408063 39958147 41568115

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 10, 8:21 AM EDT	Mesoscale Discussion	SPC	Bronx, Columbia, Dutchess, Kings, Nassau, New York and 9 more	2 hr
Aug 10, 2:03 PM EDT	Mesoscale Discussion	SPC	Suffolk	87 min
Aug 9, 11:02 PM EDT	Severe Thunderstorm Watch	SPC	Auglaize, Butler, Clermont, Darke, Hamilton, Mercer and 5 more	76 min
Aug 10, 3:31 PM EDT	Mesoscale Discussion	SPC	Adams, Cumberland, Franklin, Fulton, Huntingdon, Juniata and 2 more	89 min
Aug 10, 7:31 PM EDT	Mesoscale Discussion	SPC	Adams, Berks, Chester, Cumberland, Delaware, Lancaster and 2 more	119 min
Aug 10, 12:20 PM EDT	Mesoscale Discussion	SPC	Logan, McDowell, Mercer, Mingo, Raleigh, Summers and 1 more	85 min

Nearby

Mesoscale Discussions in Pennsylvania, 2012 Mesoscale Discussions in Ohio, 2012 Mesoscale Discussions in New York, 2012 Every mesoscale discussion in 2012

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.