Alert archive / Pennsylvania / Mesoscale Discussions in 2013

Mesoscale Discussion 1313

June 30, 20137 states

The Storm Prediction Center issued this mesoscale discussion at Jun 30, 2013, 2:33 PM EDT for 7 states. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Jun 30, 2013, 2:33 PM EDT (18:33 UTC)
Expired: Jun 30, 2013, 5:00 PM EDT
In force: 2 hr
Issued by: the Storm Prediction Center
Chance of a watch: 20%

All 74 counties

Berkshire County, MA, Franklin County, MA, Hampden County, MA, Hampshire County, MA, Middlesex County, MA, Worcester County, MA, Androscoggin County, ME, Cumberland County, ME, York County, ME, Belknap County, NH, Carroll County, NH, Cheshire County, NH, Hillsborough County, NH, Merrimack County, NH, Rockingham County, NH, Strafford County, NH, Sullivan County, NH, Bergen County, NJ, Morris County, NJ, Passaic County, NJ, Sussex County, NJ, Warren County, NJ, Chemung County, NY, Columbia County, NY, Dutchess County, NY, Orange County, NY, Putnam County, NY, Rockland County, NY, Sullivan County, NY, Ulster County, NY, Westchester County, NY, Allegheny County, PA, Armstrong County, PA, Berks County, PA, Blair County, PA, Bradford County, PA, Cambria County, PA, Cameron County, PA, Carbon County, PA, Centre County, PA, Clearfield County, PA, Clinton County, PA, Columbia County, PA, Dauphin County, PA, Elk County, PA, Fayette County, PA, Huntingdon County, PA, Indiana County, PA, Jefferson County, PA, Juniata County, PA, Lackawanna County, PA, Lebanon County, PA, Lehigh County, PA, Luzerne County, PA, Lycoming County, PA, Mifflin County, PA, Monroe County, PA, Montour County, PA, Northampton County, PA, Northumberland County, PA, Perry County, PA, Pike County, PA, Potter County, PA, Schuylkill County, PA, Snyder County, PA, Somerset County, PA, Sullivan County, PA, Susquehanna County, PA, Tioga County, PA, Union County, PA, Wayne County, PA, Westmoreland County, PA, Wyoming County, PA, Windham County, VT

The radar

The Binghamton radar (KBGM), 70 km from the middle of the area, began a volume at 18:34 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

Albany, NY (KALY), launched 12:00Z, 6.6 hours before the alert went out and 138 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: 23 J/kg
Mixed-layer CIN: -107 J/kg
Mixed-layer LCL: 860 m above ground
0-6 km bulk shear: 47 kt
0-1 km storm-relative helicity: 89 m²/s²
0-3 km storm-relative helicity: 166 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.

290 
ACUS11 KWNS 301833
SWOMCD
SPC MCD 301833 
MEZ000-MAZ000-NHZ000-CTZ000-VTZ000-NYZ000-NJZ000-PAZ000-302100-

MESOSCALE DISCUSSION 1313
NWS STORM PREDICTION CENTER NORMAN OK
0133 PM CDT SUN JUN 30 2013

AREAS AFFECTED...PORTIONS PA...SRN NY...NRN NJ...CT...MA..SRN
VT...NH...SWRN MAINE.

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

VALID 301833Z - 302100Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...LATER-DEVELOPING...NWD EXTENSION OF REGIME DISCUSSED IN
EARLIER SPC MESOSCALE DISCUSSION 1311 WILL RESULT IN FAVORABLE
CONDITIONS FOR ISOLATED SVR EXPANDING NEWD FROM MID-ATLC INTO
PORTIONS SRN/WRN NEW ENGLAND.  THIS REGIME MAY BECOME CONTIGUOUS
ACROSS CENTRAL PA WITH INITIALLY SEPARATE AREA OF ISOLATED TO WIDELY
SCATTERED STG-SVR CONVECTION FROM WRN PA TO SRN PORTIONS OF WRN NY. 
MAIN CONCERNS ARE WIND GUSTS APCHG SVR LIMITS...CAPABLE OF TREE
DAMAGE AND MINOR DAMAGE TO STRUCTURAL EXTERIORS...AS WELL AS
ISOLATED LARGE HAIL.  THREAT APPEARS TOO MRGL/ISOLATED FOR WW.

DISCUSSION...SFC MESOANALYSIS SHOWS ELONGATED AREA OF LOW
PRESSURE...CONTAINING BROAD/QUASISTATIONARY BAROCLINIC ZONE...FROM
NRN NH SWWD ACROSS CENTRAL PA.  E OF ASSOCIATED WAVY/ILL-DEFINED
FRONT...AND AWAY FROM PRE-EXISTING OUTFLOWS...SFC INSOLATION AND DEW
POINTS MID-60S TO LOW 70S ARE OFFSETTING WEAK MID-UPPER LEVEL LAPSE
RATES ENOUGH TO YIELD FAVORABLE BUOYANCY.  MODIFIED RAOBS AND FCST
SOUNDINGS SUGGEST MLCAPE WILL PEAK BETWEEN 1500-2000 J/KG DURING
NEXT 2-3 HOURS...INVOF THETAE AXIS LOCATED NEAR LNS-POU-CON-LEW
LINE...BEFORE INSTABILITY FIELD BECOMES RATHER FRAGMENTED BY
OUTFLOWS.  WRN BRANCH OF THETAE AXIS EXTENDS ACROSS PORTIONS
CENTRAL/WRN PA...IN SUPPORT OF POST-FRONTAL CONVECTION ONGOING IN
THAT AREA...ALSO CAPABLE OF SPORADIC HAIL AND MINOR WIND DAMAGE. 
OVER ENTIRE CORRIDOR...LOW-LEVEL FLOW IS WEAK...SUBSTANTIALLY
LIMITING HODOGRAPH SIZE.  HOWEVER...35-45 KT EFFECTIVE SHEAR
MAGNITUDES ARE PRESENT AND SHOULD CONTINUE THROUGH AFTN...AIDING AT
LEAST TRANSIENTLY IN TSTM ORGANIZATION.

..EDWARDS/MEAD.. 06/30/2013

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

ATTN...WFO...GYX...BOX...BTV...OKX...ALY...PHI...BGM...CTP...
PBZ...

LAT...LON   40618027 41397909 41907782 42187685 42077536 42197427
            43207265 44567046 44116977 43137070 42237147 41077359
            40457541 39827992 40618027

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jun 30, 11:48 AM EDT	Mesoscale Discussion	SPC	Burlington, Camden, Cumberland, Gloucester, Hunterdon, Mercer and 4 more	2 hr

Nearby

Mesoscale Discussions in Pennsylvania, 2013 Mesoscale Discussions in New York, 2013 Mesoscale Discussions in New Hampshire, 2013 Every mesoscale discussion in 2013

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.