Sep 10, 2013 0600 UTC Day 1 Convective Outlook

DAY 1 CONVECTIVE OUTLOOK  

   NWS STORM PREDICTION CENTER NORMAN OK
   1145 PM CDT MON SEP 09 2013

   VALID 101200Z - 111200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF THE
   NORTHEAST STATES...

   ...SYNOPSIS...
   A MID-LEVEL SHORTWAVE IMPULSE WILL MINOR OUT WITHIN CONFLUENT FLOW
   WHILE TRACKING FROM LAKE SUPERIOR AND ADJACENT ONTARIO INTO
   CNTRL/SRN QUEBEC. STRONG MID-LEVEL WSWLY FLOW ACCOMPANYING THIS
   DISTURBANCE WILL GLANCE THE UPPER GREAT LAKES REGION AND NEW
   ENGLAND...WHILE A WSWLY LOW-LEVEL JET SPREADS EWD FROM THE GREAT
   LAKES. AS THIS OCCURS...SFC LOW PRESSURE WILL DEVELOP EWD FROM SRN
   ONTARIO AND SRN QUEBEC INTO NEW ENGLAND...WITH A FRONT TRAILING SW
   OF THE LOW INTO THE CNTRL HIGH PLAINS. MEANWHILE...AN UPSTREAM
   TROUGH IN THE MID LEVELS WILL AMPLIFY INTO THE SRN CANADIAN PRAIRIE
   PROVINCES...MAINTAINING MEAN CYCLONIC FLOW OVER THE NRN PLAINS AND
   UPPER MIDWEST. A BROAD ANTICYCLONE WILL REMAIN PROMINENT OVER THE
   SERN/S-CNTRL CONUS...WITH FLANKING WEAK CYCLONES OVER THE LOWER CO
   RIVER VALLEY AND OFF THE ERN COAST OF THE FL PENINSULA.

   ...PORTIONS OF THE NORTHEAST STATES TODAY INTO THIS EVENING...
   ONE OR MORE CLUSTERS OF STRONG TO PERHAPS LOCALLY SVR THUNDERSTORMS
   MAY BE ONGOING AT THE BEGINNING OF THE PERIOD OVER WRN/NRN NEW YORK.
   THIS WOULD BE IN RESPONSE TO PRECEDING UPSCALE CONVECTIVE GROWTH
   WITHIN THE TERMINUS OF A 35-40-KT LOW-LEVEL JET CROSSING THE ERN
   GREAT LAKES. RESIDUAL NOCTURNAL INHIBITION MAY SERVE TO LIMIT THE
   SVR POTENTIAL THIS MORNING. HOWEVER...ISOLATED SVR WIND CANNOT BE
   RULED OUT DOWNWIND OF LAKES ERIE AND ONTARIO THIS MORNING AS
   ISALLOBARIC FORCING DRIVES RICHER LOW-LEVEL MOISTURE NEWD ACROSS THE
   NERN STATES...AND 30-40 KT OF UNIDIRECTIONAL CLOUD-LAYER FLOW
   POTENTIALLY SUPPORTS THE CONTINUATION OF ORGANIZED CONVECTION.

   THROUGH THE DAY...STRONGER LOW-LEVEL ASCENT ACCOMPANYING THE LLJ MAY
   HAVE A TENDENCY TO OUTPACE THE NEWD-EXPANDING REGION OF HIGHER
   THETA-E AIR SE OF THE AFOREMENTIONED SFC LOW. AT THE SAME
   TIME...MID-LEVEL HEIGHTS ARE FORECAST TO GRADUALLY RISE IN THE WAKE
   OF EARLIER CONVECTION WHOSE REMNANT DEBRIS COULD STUNT APPRECIABLE
   BOUNDARY-LAYER DESTABILIZATION. HOWEVER...STEEP MID-LEVEL LAPSE
   RATES ACCOMPANYING THE INFLUX OF AN EML PLUME WILL OVERLIE
   INCREASINGLY RICH BOUNDARY-LAYER MOISTURE -- E.G. SFC DEWPOINTS INTO
   THE 60S TO PERHAPS AROUND 70F -- TO POTENTIALLY GENERATE LARGE
   CONVECTIVE INSTABILITY ACROSS THE SLIGHT-RISK AREA.

   LATER-DAY CONVECTIVE REDEVELOPMENT CANNOT BE RULED OUT INVOF
   RESIDUAL OUTFLOW BOUNDARIES/DIFFERENTIAL HEATING ZONES...AND STRONG
   VERTICAL SHEAR WILL AID IN A CONDITIONAL POTENTIAL FOR PRIMARILY SVR
   WIND/HAIL. ANY SUCH ACTIVITY WOULD HAVE A TENDENCY OF SPREADING
   EWD/ESEWD ACROSS PORTIONS OF NEW YORK AND NEW ENGLAND BEFORE
   BECOMING INTERRUPTED BY THE INFLUX OF A STABLE MARINE LAYER CLOSER
   TO THE COAST. HOWEVER...RELATIVELY WEAK ASCENT THROUGH A DEEP LAYER
   AND LARGE UNCERTAINTY IN THE EVOLUTION OF NOCTURNAL CONVECTION AND
   ITS ENSUING IMPACT ON BOUNDARY-LAYER STATIC STABILITY BREED LOW
   CONFIDENCE IN THE EVOLUTION OF LATER GENERATIONS OF CONVECTION...IF
   ANY. IN FACT...IT IS POSSIBLE THAT MUCH...IF NOT ALL...OF THE REGION
   WOULD BE VOID OF DIURNAL CONVECTIVE REDEVELOPMENT.

   ...SERN NEB AND ADJACENT FAR NRN KS NEWD INTO WI THIS AFTERNOON AND
   EVENING...
   LIFT EMANATING FROM VERTICAL CIRCULATIONS ALONG THE SWWD-EXTENDING
   FRONT WILL AUGMENT ASCENDING BRANCHES OF PBL CIRCULATIONS ON THE
   WARMER SIDE OF THE BOUNDARY TO PROMOTE ISOLATED TO WIDELY SCATTERED
   THUNDERSTORMS. INSTABILITY WILL BE RATHER MARGINAL...THOUGH THE
   PRESENCE OF 20-45 KT OF 500-MB FLOW -- HIGHEST NORTH -- SHOULD OFFER
   SUFFICIENT DEEP SHEAR FOR A FEW SUSTAINED CELLS WITH THE POTENTIAL
   FOR ISOLATED SVR WIND. DEEP FORCING FOR ASCENT AND LIMITED BUOYANCY
   WILL BE THE PRIMARY FACTORS TO INHIBIT THE OVERALL SVR POTENTIAL.

   ...PORTIONS OF THE SOUTHWEST STATES THIS AFTERNOON AND EVENING...
   SCATTERED CONVECTION WILL ONCE AGAIN FORM AROUND THE WEAK MID-LEVEL
   CYCLONE AMIDST RESIDUAL MONSOONAL MOISTURE. STRONG WIND GUSTS WILL
   BE POSSIBLE IN AREAS THAT EXPERIENCE STRONGER SFC HEATING/STEEPER
   LOW-LEVEL LAPSE RATES. AN ISOLATED MARGINALLY SVR WIND GUST CANNOT
   BE RULED OUT. HOWEVER...THE PRESENCE OF ONLY MODEST MID-LEVEL
   FLOW/DEEP SHEAR AND ONLY MODESTLY STEEP MID-LEVEL LAPSE RATES
   PRECLUDE THE DELINEATION OF SVR WIND PROBABILITIES AT THIS TIME.

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