SPC AC 191245

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0745 AM CDT FRI JUL 19 2013

   VALID 191300Z - 201200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS FROM PARTS OF THE UPPER MIDWEST
   TO NRN NEW ENGLAND...

   ...SYNOPSIS...

   A LONG-WAVE TROUGH --ANCHORED BY AN UPPER-LEVEL LOW OVER NWRN
   QUEBEC-- WILL INTENSIFY ACROSS THE ERN HALF OF CANADA AND THE GREAT
   LAKES OWING TO THE SEWD PROGRESSION OF A STRONG VORTICITY MAXIMUM
   CURRENTLY OVER NERN MANITOBA.  THIS FEATURE WILL BE PRECEDED BY A
   WEAKER VORTICITY RIBBON WHICH WILL MOVE FROM NRN MN SEWD THROUGH THE
   UPPER GREAT LAKES.  ELSEWHERE...A MID TO UPPER-LEVEL LOW --COLD CORE
   IN NATURE-- WILL SLOWLY SHIFT WWD ACROSS LA INTO ERN TX.  

   IN THE LOW LEVELS...THE ERN PORTION OF A COLD FRONT FROM THE MN
   ARROWHEAD SWWD THROUGH THE MID MO VALLEY INTO CNTRL HIGH PLAINS WILL
   ADVANCE SEWD THROUGH THE UPPER GREAT LAKES.  MEANWHILE...THE WRN
   SEGMENT WILL MOVE NWD AS A WARM FRONT...EVENTUALLY LINKING WITH A
   LEE CYCLONE DEVELOPING EWD FROM ERN WY INTO WRN SD.  

   ...UPPER MIDWEST/GREAT LAKES THIS AFTERNOON AND TONIGHT...

   DESPITE ONLY MODEST MIDLEVEL LAPSE RATES PER 12Z SOUNDINGS...
   ABUNDANT SUNSHINE COUPLED WITH BOUNDARY LAYER DEWPOINTS IN THE UPPER
   60S TO LOWER 70S WILL CONTRIBUTE TO A MODERATELY UNSTABLE AIR MASS
   BY AFTERNOON WITH MLCAPE VALUES OF 1500-2500 J/KG.  FORCING FOR
   ASCENT/DCVA ASSOCIATED WITH THE ABOVE-MENTIONED LEAD VORTICITY
   RIBBON WILL AUGMENT GENERALLY WEAK LOW-LEVEL CONVERGENCE TO SUPPORT
   THE INTENSIFICATION OF THE ONGOING PRE-FRONTAL TSTM BAND CURRENTLY
   FROM THE U.P. OF MI SWWD TO ERN NEB AS OF 12Z.  ADDITIONAL STORMS
   WILL BE POSSIBLE DOWNSTREAM FROM THIS ACTIVITY ALONG DEVELOPING LAKE
   BREEZE BOUNDARIES AND/OR CONFLUENCE LINES AS WELL AS ALONG THE
   SYNOPTIC COLD FRONT.

   GIVEN A DEEP WLY WIND FIELD THAT WILL STEADILY STRENGTHEN THROUGH
   THE DAY...THE SETUP WILL BE SUPPORTIVE OF BOWING LINE SEGMENTS AND
   EMBEDDED SUPERCELL STRUCTURES CAPABLE OF DAMAGING WINDS AND SOME
   HAIL.  THIS THREAT WILL LIKELY SPREAD EWD INTO THE LOWER GREAT LAKES
   BY TONIGHT WITH A CONTINUED RISK FOR MAINLY DAMAGING WIND GUSTS.

   ...NRN NEW ENGLAND TODAY AND TONIGHT...

   MULTIPLE ROUNDS OF TSTMS WILL BE POSSIBLE DURING THE FORECAST
   PERIOD...THE FIRST OF WHICH WILL MOVE ACROSS PARTS OF NRN AND CNTRL
   MAINE THIS MORNING INTO AFTERNOON.  THE CONVECTIVE OUTFLOW BOUNDARY
   ESTABLISHED BY THESE INITIAL STORMS AND THE SYNOPTIC WARM FRONT
   LIFTING NEWD ACROSS THE REGION WILL LIKELY SERVE AS THE PRIMARY FOCI
   FOR IN-SITU STORM DEVELOPMENT LATER TODAY.  OTHERWISE...EXPECT
   STORMS TO EVOLVE ACROSS SWRN PARTS OF ONTARIO AND QUEBEC BEFORE
   MOVING INTO THE AREA.  THE COMBINATION OF MODERATE AMOUNTS OF
   INSTABILITY AND VERTICAL SHEAR WILL BE SUPPORTIVE OF ORGANIZED STORM
   MODES...INCLUDING BOWING STRUCTURES AND SUPERCELLS.  THE PRIMARY
   HAZARD WILL BE DAMAGING WINDS...THOUGH SOME HAIL AND PERHAPS A
   TORNADO ARE POSSIBLE.  
     
   ...NRN/CNTRL HIGH PLAINS THIS AFTERNOON INTO TONIGHT...

   THE ISALLOBARIC RESPONSE TO THE DEVELOPING WY LEE CYCLONE WILL
   RESULT IN STRENGTHENING SELY LOW-LEVEL WINDS BY AFTERNOON ALONG WITH
   THE NWD DEVELOPMENT OF THE SURFACE FRONT.  DEEP BOUNDARY LAYER
   MIXING WILL LIKELY OFFSET ANY MEANINGFUL MOISTURE ADVECTION WITH
   DEWPOINTS REMAINING IN THE UPPER 40S TO MID 50S.  HOWEVER...THE
   REGION WILL RESIDE ALONG THE ERN FRINGE OF INTERMOUNTAIN WEST EML
   WHICH WILL SUPPORT MLCAPE VALUES APPROACHING 1000-1500 J/KG AMIDST A
   KINEMATIC ENVIRONMENT FEATURING A VERTICALLY VEERING WIND PROFILE
   WITH AROUND 35 KT OF DEEP-LAYER SHEAR.

   OROGRAPHIC FORCING COUPLED WITH CONVERGENCE INVOF THE SURFACE LOW
   AND RETREATING FRONT ARE EXPECTED TO FOSTER ISOLATED TO WIDELY
   SCATTERED TSTM DEVELOPMENT BY MID TO LATE AFTERNOON...A FEW OF WHICH
   MAY BECOME SEVERE WITH A RISK FOR HAIL AND LOCALLY DAMAGING WIND
   GUSTS.  OTHER ELEVATED STORMS MAY DEVELOP TO THE NORTH OF THE
   SURFACE FRONT TONIGHT OVER WRN SD WHERE WAA AND ISENTROPIC ASCENT
   ARE ENHANCED AT THE TERMINUS OF A NOCTURNAL LOW-LEVEL WIND MAXIMUM. 
   SOME HAIL WILL BE POSSIBLE WITH THESE STORMS.

   ...ERN TX/LA INTO THE OZARK PLATEAU THIS AFTERNOON AND EVENING...

   SIMILAR TO PAST DAYS...THE MID TO UPPER-LEVEL LOW MENTIONED IN THE
   SYNOPSIS WILL INTERACT WITH A MOIST AND MODERATELY UNSTABLE AIR MASS
   TO PROMOTE SCATTERED TO NUMEROUS STORMS THROUGH THE PEAK OF THE
   DIURNAL HEATING CYCLE.  THE STRONGEST STORMS WILL BE CAPABLE OF
   WET-MICROBURST-RELATED WIND DAMAGE INTO THIS EVENING.

   ..MEAD/JIRAK.. 07/19/2013

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