SPC AC 170510

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1210 AM CDT Thu Aug 17 2017

   Valid 181200Z - 191200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE MIDDLE
   ATLANTIC INTO UPSTATE NY...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE MID
   MO VALLEY REGION...

   ...SUMMARY...
   Scattered thunderstorms, a few possibly severe, are expected from
   the Middle Atlantic into Upstate New York. Isolated severe
   thunderstorms are also expected across the mid Missouri Valley
   region.

   ...Middle Atlantic/Upstate NY...

   Central Plains short-wave trough will translate into the OH Valley
   by the beginning of the day2 period. Associated surface front is
   expected to migrate to a position from southern ON, south across
   western PA into WV by 18z. High PW air mass will extend across the
   warm sector ahead of the wind shift and large-scale forcing for
   ascent will encourage considerable amount of frontal convection that
   should be ongoing at the start of the period. Latest short-range
   guidance suggests modest boundary-layer heating should occur from
   western VA, north into Upstate NY where surface-3km lapse rates
   could exceed 7 C/km. As a result, adequate buoyancy is expected
   along this corridor for robust thunderstorm development by early
   afternoon. With deep-layer shear expected to increase ahead of the
   front it appears organized convection is possible and damaging winds
   could be noted with the strongest convection. Have expanded 5%
   severe probs south into the Delmarva where modest instability will
   exist along southern periphery of stronger forcing. SLGT risk may
   need to be added to this region if later guidance continues to
   suggest thermodynamic profiles will support strong updrafts.

   ...Mid MO Valley Region...

   Strong short-wave trough is expected to dig southeast across the
   northern Plains into the mid MO Valley by late afternoon. 500mb flow
   in excess of 40kt should extend across eastern NE into IA coincident
   with isolated convection that should evolve ahead of a weak surface
   front that will extend from the SD/MN border, south into
   north-central KS. Strong boundary-layer heating will be noted across
   the plains and cooling temperatures aloft will enhance lapse rates
   within strongly sheared environment. While low-level convergence
   will not be particularly strong, isolated thunderstorms should
   evolve ahead of the short wave then track southeast toward northwest
   MO. Hail/wind are the primary threats with this activity.

   ..Darrow.. 08/17/2017

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   NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z