SPC AC 110558

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1158 PM CST Tue Dec 10 2024

   Valid 111200Z - 121200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PARTS OF
   SOUTHERN NEW ENGLAND ALONG THE ATLANTIC COAST SOUTH TO FAR
   NORTHEASTERN NORTH CAROLINA...

   ...SUMMARY...
   Isolated severe thunderstorms are possible today across the East
   Coast States, as far north as southern New England. The most
   probable area for a few tornadoes and damaging winds appears to be
   centered on eastern North Carolina from midday onward.

   ...Synopsis...
   South of a closed low over the western Ontario area, a
   strong/high-amplitude trough initially aligned roughly along the
   Mississippi Valley will shift rapidly eastward and then
   northeastward, acquiring substantial negative tilt with time.  

   At the surface, a cold front will sweep eastward, clearing most of
   the coast through the afternoon, and eventually shifting southward
   and off the southern Florida coast/the Keys during the evening
   hours.

   ...Southern Atlantic Coast states...
   As a cold front advances eastward across the East Coast states
   through the morning and afternoon hours, strong ascent forced by the
   potent/advancing upper trough will support showers and embedded
   thunderstorms within the weakly unstable warm sector.

   Despite the thermodynamic deficiencies that are expected, a high-end
   wind field will exist, with flow veering gradually and increasing
   rapidly in magnitude with height.  Resulting shear will favor
   supercells with any semi-discrete storms, while linear organization
   is also expected in an overall mixed-mode evolution.  Along with
   potential for damaging wind gusts, a few tornadoes are also
   expected.  The greatest risk appears to exist across the eastern
   North Carolina/Coastal Plain area, during the afternoon.  Weaker
   flow aloft farther south into Florida suggests limiting southern
   extent of the SLGT risk area to the far northeastern South Carolina
   vicinity, similar to prior forecasts.  Risk will end in most areas
   by late afternoon, as the front moves offshore in all areas except
   Florida, before finally clearing the Peninsula after dark.

   ...Mid-Atlantic region to southern New England...
   As a surface low deepens over the central Appalachians region and
   moves quickly northward through the day, low-topped convection near
   the trailing cold front may evolve into broken linear segments.  The
   boundary layer is forecast to remain stable, with potential a couple
   hundred J/kg CAPE above 850 to 900mb, sufficient for
   occasional/sporadic lightning.  

   Meanwhile, extremely strong low-level flow is expected, which will
   support very fast-moving convection.  Given the strongly dynamic
   synoptic setup as the upper trough takes on increasingly negative
   tilt, the overall setup suggests locally strong wind gusts despite
   the surface-based stable layer.  As such, will raise damaging wind
   probability to 15% and thus introduce SLGT risk to parts of southern
   New England and coastal areas of the Mid-Atlantic region, with some
   gusts in excess of 60 MPH expected.

   ..Goss/Moore.. 12/11/2024

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