MESO: Mesoscale Discussion 1270

ACUS11 KWNS 271957
SWOMCD
SPC MCD 271957
CTZ000-NYZ000-NJZ000-PAZ000-DEZ000-MDZ000-272130-

MESOSCALE DISCUSSION 1270
NWS STORM PREDICTION CENTER NORMAN OK
0257 PM CDT THU JUN 27 2013

AREAS AFFECTED...PARTS OF THE NORTHEAST

CONCERNING...TORNADO WATCH 377...

VALID 271957Z - 272130Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 377 CONTINUES.

SUMMARY...RISK FOR ISOLATED DAMAGING WINDS AND A TORNADO OR TWO
SHOULD GRADUALLY DEVELOP E/NEWD ACROSS PRIMARILY ERN PA/MD...DE AND
NJ. A DOWNSTREAM WW ISSUANCE IS PROBABLE BY EARLY EVENING IN
PORTIONS OF NERN PA TO SRN NY.

DISCUSSION...STRONGEST/LONGEST-LIVED HIGH REFLECTIVITY CORES HAVE
PERSISTED IMMEDIATELY AHEAD OF AN MCV CENTERED JUST S OF UNV AS OF
1945Z. CO-LOCATED WITH THE PRIMARY SURFACE CYCLONE AND WITH MODEST
SURFACE PRESSURE FALLS DOWNSTREAM...A SUPERCELL WAS NOTED EARLIER IN
JUNIATA/PERRY COUNTY PA BUT HAS SINCE DISSIPATED. SUFFICIENT
LOW/MID-LEVEL SHEAR HAS BEEN SAMPLED BY CCX VWP DATA TO SUPPORT
TRANSIENT SUPERCELL STRUCTURES AMIDST A RELATIVELY CHAOTIC
CONVECTIVE MODE. WITH ADDITIONAL TSTMS DEVELOPING IN ASSOCIATION
WITH A SECOND MCV SHIFTING NEWD ACROSS CNTRL MD AND RELATIVELY
PROMINENT CU FIELD DOWNSTREAM IN THE NORTHEAST...STRONG TO SEVERE
CONVECTION WILL LIKELY BE SUSTAINED FOR THE NEXT SEVERAL HOURS. A
CONSOLIDATED CLUSTER MAY ULTIMATELY EVOLVE NEWD WITH A RISK FOR
MAINLY DAMAGING WINDS AND PERHAPS A TORNADO.

TO THE SW OF THE MCV/S...SEVERE THREAT IS NIL AND PORTIONS OF WW IN
VA/DC COULD BE SAFELY CLEARED.

..GRAMS.. 06/27/2013

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

ATTN...WFO...OKX...ALY...PHI...BGM...CTP...LWX...

LAT...LON 39207663 39727715 40127749 40887726 41577626 42307452
42237378 41827342 40877355 39237448 38537541 38877620
39207663

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