ZCZC SPCSWOMCD ALL ACUS11 KWNS 091909 SPC MCD 091909 NJZ000-PAZ000-DEZ000-MDZ000-DCZ000-VAZ000-WVZ000-092045- MESOSCALE DISCUSSION 1341 NWS STORM PREDICTION CENTER NORMAN OK 0209 PM CDT THU JUL 09 2015 AREAS AFFECTED...PA/MD/NORTHERN WV TO NORTHERN VA AND DE/NJ CONCERNING...TORNADO WATCH 397... VALID 091909Z - 092045Z THE SEVERE WEATHER THREAT FOR TORNADO WATCH 397 CONTINUES. SUMMARY...DAMAGING WIND/ISOLATED TORNADO POTENTIAL IS EXPECTED TO INCREASE/SPREAD EASTWARD THROUGH LATE AFTERNOON ACROSS PARTS OF PA AND NEARBY NORTHERN WV/MD. TORNADO WATCH 397 CONTINUES UNTIL 01Z. AN ADDITIONAL WATCH IS LIKELY BY LATE AFTERNOON /APPROX 20-21Z/ ESPECIALLY FOR PORTIONS OF EASTERN PA AND NJ/DE/NORTHEAST MD. DISCUSSION...18Z SUBJECTIVE SURFACE ANALYSIS FEATURES AN EASTWARD-MOVING SURFACE LOW ACROSS FAR WESTERN NY/NORTHWEST PA...WITH PRECEDING 2-3 MB TWO-HOURLY PRESSURE FALLS ACROSS SOUTH-CENTRAL NY/NORTH-CENTRAL PA. A WAVY/NORTHWARD-SHIFTING WARM FRONT EXTENDS EAST-SOUTHWARD FROM THE SURFACE LOW ACROSS ACROSS NORTH-CENTRAL/EASTERN PA INTO NJ. AS OF 19Z/3PM EDT...A NARROW/BOWING CONVECTIVE LINE CONTINUES TO GRADUALLY GROW UPSCALE AND MOVE EASTWARD ACROSS SOUTHWEST PA/FAR WESTERN MD...WHILE FARTHER NORTH...WITH OTHER LOWER-TOPPED SEMI-DISCRETE STORMS INCLUDING A COUPLE OF SUPERCELLS CONTINUE TO FLUCTUATE INTENSITY-WISE ACROSS WEST-CENTRAL PA. AHEAD OF THIS ACTIVITY...VISIBLE SATELLITE IMAGERY SUGGESTS THAT THE CUMULUS FIELD CONTINUES TO BECOME INCREASING AGITATED/DEEPEN WITHIN THE WARM SECTOR PARTICULARLY ACROSS PA/NJ WHERE MLCAPE IS ESTIMATED TO BE AT LEAST 500-1000 J/KG COINCIDENT WITH UPPER 60S/LOWER 70S F SURFACE DEWPOINTS. SIMILAR TO PREVIOUSLY DESCRIBED CONVECTIVE TRENDS...LATEST THINKING IS THAT THE EASTWARD-MOVING BAND OF STORMS WILL CONTINUE TO GROW UPSCALE/ACCELERATE EASTWARD ACROSS EASTERN/NORTHERN WV AND MD/SOUTHERN PA...WITH OTHER SEMI-DISCRETE STORMS/SUPERCELLS REMAINING A DISTINCT POSSIBILITY FARTHER NORTH /AND POSSIBLY EAST AHEAD OF THE LINE/ ACROSS ADDITIONAL PORTIONS OF PA/NJ AND DELMARVA VICINITY. WHILE DAMAGING WINDS ARE LIKELY TO BE THE MOST PREVALENT RISK...TORNADO POTENTIAL WILL EXIST...PARTICULARLY WITH ANY SUPERCELLS INTERACTING WITH THE WARM FRONT ACROSS PA/NJ. LATEST WSR-88D VWP DATA FROM STATE COLLEGE IS SAMPLING 0-1 KM SRH OF APPROXIMATELY 200 M2/S2...WITH LOCALLY HIGHER VALUES WHERE LOW-LEVEL WINDS ARE BACKED TO MORE SOUTHEASTERLY /SUCH AS THE THE WILLIAMSPORT VICINITY AS OF 18Z-19Z/. ..GUYER.. 07/09/2015 ...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT... ATTN...WFO...OKX...PHI...BGM...CTP...LWX...PBZ...RLX... LAT...LON 40977926 41477889 41857748 41747597 41247498 40597431 39337483 38847584 38797686 39147828 39137948 39308016 40977926 NNNN