THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE LOWER GREAT

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Categorical Graphic
Probabilistic Tornado Graphic
Probability of a tornado within 25 miles of a point. Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point.
Probabilistic Damaging Wind Graphic
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point. Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Probabilistic Large Hail Graphic
Probability of hail 1" or larger within 25 miles of a point. Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point.

   SPC AC 171608      DAY 1 CONVECTIVE OUTLOOK     NWS STORM PREDICTION CENTER NORMAN OK   1108 AM CDT TUE JUL 17 2012      VALID 171630Z - 181200Z      ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE LOWER GREAT   LAKES AND NEW ENGLAND...      ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NRN HIGH   PLAINS...      ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF WI...      ...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE SOUTHEASTERN   STATES...      ...SYNOPSIS...      SHORTWAVE TROUGH AND ASSOCIATED 50-60 KT MIDLEVEL JET STREAK OVER   ONTARIO WILL PROGRESS ESEWD ACROSS SRN QUEBEC AND NRN NEW   ENGLAND...CONTRIBUTING TO INCREASING VERTICAL SHEAR AND LARGE-SCALE   FORCING FOR ASCENT OVER THESE REGIONS THIS AFTERNOON INTO TONIGHT.    ELSEWHERE...A SHORTWAVE TROUGH OVER WRN WY WILL CONTINUE NEWD INTO   THE WRN DAKOTAS BY TONIGHT...WHILE FARTHER W AN UPPER LOW WILL   REMAIN QUASI-STATIONARY ALONG THE SWRN ORE/NWRN CA COASTS.    FINALLY...AN UPPER LOW OVER NERN FL WILL DRIFT NNWWD TOWARD THE   SAVANNAH RIVER VALLEY.      AT THE SURFACE...LOW PRESSURE OVER SWRN ONTARIO WILL DEVELOP ENEWD   INTO NRN ME BY 18/00Z WHILE TRAILING COLD FRONT SETTLES SWD THROUGH   THE ST. LAWRENCE VALLEY...NRN NEW ENGLAND AND THE GREAT LAKES.  THE   WRN EXTENSION OF THIS BOUNDARY WILL LINK WITH A SECONDARY SURFACE   LOW WHICH IS FORECAST TO REMAIN QUASI-STATIONARY ALONG THE SD-NEB   BORDER.        ...LOWER GREAT LAKES INTO NEW ENGLAND THIS AFTERNOON AND EVENING...      AS MENTIONED ABOVE...DEEP-LAYER WLY WIND FIELD /AND RESULTANT   VERTICAL SHEAR/ WILL STRENGTHEN ACROSS THE AREA TODAY IN CONCERT   WITH PROGRESSIVE SHORTWAVE TROUGH.  THIS AIRFLOW REGIME WILL ALSO   PROMOTE THE EWD ADVECTION OF STEEP MIDLEVEL LAPSE RATES OBSERVED BY   THE 12Z APX AND DTX SOUNDINGS INTO THE LOWER GREAT LAKES.  WHEN   COUPLED WITH DECREASING CLOUDS AND BOUNDARY LAYER DEWPOINTS IN THE   60S...ENVIRONMENT IS EXPECTED TO BECOME MODERATELY UNSTABLE BY   AFTERNOON WITH MLCAPE VALUES INCREASING TO 1000-2000 J/KG.      LATEST CONVECTION-ALLOWING AND MESOSCALE MODEL GUIDANCE SUGGESTS   THAT TSTMS WILL INITIATE THIS AFTERNOON ALONG COLD FRONT OVER THE   ST. LAWRENCE VALLEY WITH ACTIVITY GROWING UPSCALE INTO A BROKEN   CONVECTIVE BAND AS IT PROGRESSES SEWD INTO NRN NEW ENGLAND AND   UPSTATE NY.  MORE ISOLATED STORM DEVELOPMENT WILL ALSO BE POSSIBLE   THIS AFTERNOON ALONG DEVELOPING LAKE BREEZE FRONT IN THE LEE OF   LAKES ERIE AND ONTARIO...AS WELL AS WRN EXTENSION OF COLD FRONT IN   LOWER MI.      THE STRONGEST LOW AND DEEP-LAYER SHEAR WILL RESIDE FROM THE   ADIRONDACKS EWD ACROSS NRN PARTS OF VT/NH INTO ME WHERE THE   POTENTIAL WILL EXIST FOR SUPERCELLS AND BOWING STRUCTURES CAPABLE OF   A COUPLE TORNADOES...DAMAGING WINDS AND LARGE HAIL.  VERTICAL SHEAR   WILL DECREASE SWD ACROSS THE SLIGHT RISK AREA...THOUGH THE MODERATE   INSTABILITY WILL STILL PROMOTE VIGOROUS UP/DOWNDRAFTS CAPABLE OF   DAMAGING WINDS AND HAIL.      FOR ADDITIONAL NEAR-TERM GUIDANCE...SEE MCD 1480.      ...SERN STATES THIS AFTERNOON AND EVENING...      12Z 500-MB ANALYSIS AND REGIONAL SOUNDING DATA INDICATED A POCKET OF   COLDER AIR IN THE MIDLEVELS /I.E. -8 TO -9 C/ WHICH WILL COMBINE   WITH PW VALUES OF 1.75-2.00 INCHES AND DAYTIME HEATING TO YIELD   AFTERNOON MLCAPE OF 2000-3000+ J/KG.  CONVERGENCE INVOF OF LOW-LEVEL   CIRCULATION EVIDENT IN VISIBLE SATELLITE OVER CNTRL GA AS OF 15Z AND   ASSOCIATED SURFACE TROUGH WILL LIKELY SERVE AS THE FOCI FOR   SCATTERED-NUMEROUS TSTMS THIS AFTERNOON.  WHILE VERTICAL SHEAR WILL   REMAIN WEAK...THE DEGREE OF INSTABILITY WILL PROMOTE PULSE AND   MULTICELL STORM CLUSTERS CAPABLE OF LOCALLY DAMAGING WINDS AND SOME   HAIL.      ...NRN HIGH PLAINS THIS AFTERNOON INTO TONIGHT...      SHORTWAVE TROUGH MENTIONED IN SYNOPSIS WILL AUGMENT LOW-LEVEL   CONVERGENCE ALONG INVERTED SURFACE TROUGH TO GIVE RISE TO WIDELY   SCATTERED TSTMS THIS AFTERNOON OVER ERN MT/NERN WY INTO THE WRN   DAKOTAS.  WHILE VERTICAL SHEAR WILL NOT BE PARTICULARLY   STRONG...VERTICALLY VEERING WIND PROFILES WILL COINCIDE WITH STEEP   MIDLEVEL LAPSE RATES AND A MOIST BOUNDARY LAYER TO PROMOTE LOOSELY   ORGANIZED STORM CLUSTERS WITH A RISK FOR LOCALLY DAMAGING WINDS AND   HAIL.      ...WI THIS AFTERNOON AND EVENING...      MULTI-MODEL CONSENSUS SUGGESTS AN INCREASING RISK FOR SURFACE-BASED   TSTMS BY MID-LATE AFTERNOON ALONG THE SWD-MOVING COLD FRONT WITH   ACTIVITY PERHAPS BEING AIDED BY A WEAK MIDLEVEL IMPULSE CURRENTLY   OVER NRN MN.  MODIFICATION OF 12Z GRB SOUNDING FOR ANTICIPATED   AFTERNOON CONDITIONS SUGGESTS THAT CAP WOULD BE ELIMINATED FOR   SURFACE TEMPERATURES IN THE MID 90S.  GIVEN THE MOIST BOUNDARY LAYER   AND RESULTANT MLCAPE OF 2000-3000 J/KG...AS WELL AS MODEST WLY   MIDLEVEL FLOW...SETUP MAY YIELD A FORWARD-PROPAGATING CLUSTER OF   TSTMS/MCS WITH AN ASSOCIATED RISK FOR DAMAGING WINDS AND HAIL.      ...INTERIOR PACIFIC NW AND NRN INTERMOUNTAIN REGION THIS AFTERNOON   AND EVENING...      MORNING WATER VAPOR IMAGERY SHOWS A SERIES OF VORTICITY MAXIMA   PIVOTING AROUND PARENT UPPER LOW.  FORCING ASSOCIATED WITH THESE   FEATURES WILL COMBINE WITH MODEST LAPSE RATES AND PW VALUES OF   1.00-1.40 INCHES TO FOSTER WIDELY SCATTERED STORMS CAPABLE OF GUSTY   WINDS AND PERHAPS SOME HAIL.      ..MEAD/HURLBUT.. 07/17/2012      NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z   CURRENT UTC TIME: 1617Z (11:17AM), RELOAD THIS PAGE TO UPDATE THE TIME