SPC AC 100523

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1223 AM CDT Sat Oct 10 2020

   Valid 101200Z - 111200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE GULF
   STATES AND FROM NEW YORK TO NEW ENGLAND...

   ...SUMMARY...
   A few tornadoes are possible on Saturday across parts of the Gulf
   States.  Severe gusts are also expected across parts of northern New
   York into western Maine.

   ...Tropical Cyclone Delta...

   Tropical Cyclone Delta continues its northeast movement across LA
   early this morning. As TC Delta lifts into northwest MS later by
   18z, significant mid-level drying will surge east and the primary
   corridor of deepest convection should become focused from
   south-central AL into west-central GA.

   Latest model guidance does not allow appreciable buoyancy to develop
   immediately ahead of Beta over northern MS, and forecast soundings
   strongly suggest updrafts will struggle to attain heights necessary
   for lightning. Even so, strong low-level shear warrants at least low
   probabilities for locally strong winds or perhaps a brief tornado.
   Otherwise, the primary focus for more robust convection should focus
   downstream where partial breaks in cloud cover should allow for some
   boundary-layer heating and appreciably more instability, especially
   from southern AL into west-central GA. While this region will be
   along the eastern fringe of stronger low-level shear, forecast
   soundings exhibit adequate shear for supercells. Have extended
   wind/tornado probabilities downstream into the stronger region of
   instability where adequate shear will exist for sustained, robust
   updrafts. A few tornadoes and gusty winds are possible with this
   activity.

   ...NY to ME...

   Early-morning water-vapor imagery depicts at least two distinct
   short-wave troughs over ON. The lead feature will quickly shift into
   QC as the upstream short wave digs southeast toward the
   international border region later this afternoon. Focused mid-level
   height falls will spread across QC/northern New England with more
   appreciable falls expected after 11/00z over ME. A plume of
   higher-PW air will be drawn ahead of the front prior to this wind
   shift advancing south of the Canadian border. It appears warm-sector
   temperatures will warm quickly ahead of the front which will lead to
   convective development as minimal surface convergence will be needed
   for parcels to reach their LFC. Latest HREF supports this and
   scattered thunderstorms should evolve along the boundary across
   southeast ON/northern NY by 18z then spread southeast as the front
   surges toward New England. Increasingly westerly flow will favor the
   potential for gusty winds with this convection. With the mean flow
   expected to be parallel with this frontal convection, this could
   lessen more intense bow-type structures. For this reason, will
   maintain 15 percent severe wind probabilities.

   ..Darrow/Moore.. 10/10/2020

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