Severe tstorm / heavy rain threat

Strong cold front will approach the region tomorrow with associated showers and thunderstorms. Strong unidirection flow will promote some bows with damaging winds through tomorrow night. Total totals, CAPE, and lifted indices are low for a severe threat, however significant speed shear is expected and latest model projected SWEAT index is high. Using latest GFS and NAM runs, KeeneWeather Severe Index (KWSI) is returning a 35 to 40% chance for thunderstorms, a 20 to 25% chance for severe thunderstorms in the form of multicell lines and perhaps a few super cells. Main threat is damaging wind, with flash flooding a potential issue due to expected PWATs around 1.5".

NWS:

MODELS CONTINUE TO ADVERTISE THE APPROACH OF A VIGOROUS COLD FRONTFOR THURSDAY. BELIEVE WE HAVE A VERY GOOD CHANCE FOR MANY GUSTS 50 KNOTS WITH THE NARROW LINE OF SCT TO BKN CONVECTION ATTENDING THE FRONT BARRELING INTO A HOT AIRMASS THAT HAS ITS OWN PRE CONVECTION GUSTY SOUTHWEST WINDS TO 30-35KTS.

THURSDAY APPEARS TO BE A HOT DAY THAT WILL FEATURE WIND.

CONTINUITY WITH PREV 4PM TUE FCST EXCEPTING RAISED POPS SLIGHTLY IN NW MASS FOR THE LATE DAY LINE...THIS IN LINE WITH 21Z SREF POPS.

PLS SEE SPC DAY 2 DISCUSSIONS ON THE SUBJECT OF SVR. SOUNDINGS HAVE 40+ KNOTS 10000 FT.

OVERALL...LOOKING AT A GOOD CHANCE OF SHOWERS AND TSTMS DURING THE AFTERNOON ON THURS...MAINLY ACROSS THE NORTHWESTERN HALF OF THE CWA. HAVE HIGH CHANCE/LOW LIKELY POPS LATE THURS AFTN INTO THURS NITE FOR THIS AREA. GIVEN THE KINEMATIC AND THERMODYNAMIC PROFILES THAT ARE PRESENTLY MODELED...SEVERE THUNDERSTORMS WILL BE POSSIBLE LATER THURS AFTN AND EVENING...WITH THE BEST CHANCES TO THE WEST OF I-495 AND NORTH OF I-84. CONTINUED HIGH CHANCES FOR SHOWERS AND TSTMS FOR MUCH OF THE AREA FOR THURS NIGHT. WIND FIELDS VERY STRONG AND AM IMPRESSED ABOUT THE POTENTIAL FOR BOWS IN UNIDIRECTIONAL FLOW. THIS LOOKS LIKE A BIG WIND DAMAGE DAY FOR A PTN OF SNE "IF" CONVECTION FIRES AS ANTICIPATED. MORE LATER.

HPC:

DAYS 2/3...

...CENTRAL PLAINS TO THE NORTHEAST/MID ATLANTIC STATES...

A SLOW MOVING COLD FRONT ASSOCIATED WITH THE MID/UPR TROF CENTERED ACROSS THE GREAT LAKES IS FORECAST TO DROP SWD THRU THE REGION WHILE REMAINING A FOCUS FOR WIDESPREAD LGT/MDT WITH POCKETS OF HVY PCPN THRU THE PERIOD. HEAVIEST AMTS ARE FORECAST TO OCCUR FROM THE MID MS VLY THRU THE OH VLY INTO THE CTRL APPALACHIANS WHERE THE MODELS SHOW THE DEEPEST MOISTURE POOL AS WELL AS SEVERAL WEAK IMPULSES MOVING ALONG THE BASE OF THE TROF. AS NOTED IN THE PMDHMD...THE GFS IS EXHIBITING FEEDBACK PROBLEMS HERE AND IS LIKELY OVER-AMPLIFYING THE IMPULSE IT DEPICTS MOVING THRU THE MID MS VLY LATE THU...IN TURN OVERDEEPENING THE SFC WAVE AND CARRYING THE SFC BNDRY TOO FAR TO THE N ACROSS THE OH VLY ON FRI. OPTED AWAY FROM THIS SOLUTION...INSTEAD CHOOSING A BLEND OF THE NAM/21Z SREF MEAN/12Z ECMWF...WHICH WERE FAIRLY SIMILAR AND MORE REASONABLE IN THEIR DEPICTION OF THE SFC PATTERN HERE.

SPC:

...NEW ENGLAND/CNTRL APPALACHIANS/NY/PA/NJ...
AN UPPER-LEVEL TROUGH OVER THE GREAT LAKES REGION TONIGHT IS FORECAST TO MOVE EWD INTO THE NERN STATES THURSDAY. AT THE SFC...A COLD FRONT WILL ADVANCE SEWD INTO NEW ENGLAND AND THE CNTRL APPALACHIAN MTNS. SFC HEATING...LOW-LEVEL CONVERGENCE ALONG THE BOUNDARY AND LARGE-SCALE ASCENT ASSOCIATED WITH THE UPPER-LEVEL TROUGH WILL SUPPORT SCATTERED TO NUMEROUS THUNDERSTORM DEVELOPMENT THURSDAY AFTERNOON.

AT MID-LEVELS...A 55 TO 70 KT JET MAX IS FORECAST TO OVERSPREAD THE SLIGHT RISK AREA THURSDAY RESULTING IN FAVORABLE SHEAR ENVIRONMENT FOR SEVERE STORMS. FORECAST SOUNDINGS ACROSS THE REGION THURSDAY AFTERNOON SHOW 0-6 KM SHEAR VALUES IN THE 40 TO 50 KT RANGE WHICH SHOULD BE SUFFICIENT FOR AN ISOLATED SUPERCELL AND HAIL THREAT ESPECIALLY IN AREAS WITH MAXIMIZED INSTABILITY. HOWEVER...UNIDIRECTIONAL LOW TO MID-LEVEL WINDS SHOULD ALSO BE SUPPORTIVE OF LINE SEGMENTS WITH WIND DAMAGE POTENTIAL IN THE LATE AFTERNOON WHEN LOW-LEVEL LAPSE RATES ARE FORECAST TO BE STEEPEST.