SPC AC 300550

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1150 PM CST Sun Nov 29 2020

   Valid 301200Z - 011200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE EASTERN
   CAROLINAS INTO SOUTHERN NEW ENGLAND...

   ...SUMMARY...
   Isolated strong to severe thunderstorms capable of producing
   damaging winds and a couple of tornadoes will be possible today from
   parts of Florida into the Carolinas, Mid-Atlantic and southern New
   England.

   ...Synopsis...
   Remnants of an upper low crossing the southern Appalachians region
   early in the period will continue to be absorbed by a sharp
   northern-stream trough, progged to be crossing the upper Great
   Lakes/Mississippi Valley at the start of the period.  As this trough
   advances, and fully ingests the remnant upper low, the trough is
   expected to gradually close off and become its own large upper
   cyclone -- which will reach the central Appalachians area by the end
   of the period.

   As the upper flow field evolves, a deepening surface low crossing
   western North Carolina/Virginia early in the period will move
   quickly northward, reaching central New York by 01/00Z where it will
   then begin to occlude.  The trailing cold front associated with the
   low will move across the Atlantic Coast states through the day,
   likely clearing the coast from the Mid Atlantic region to Florida
   through the evening, while a warm sector lingers onshore over
   southern New England into the overnight hours.

   ...Eastern Carolinas to southern New England...
   Widespread showers and embedded thunderstorms are forecast to be
   ongoing at the start of the period over the eastern U.S., with the
   main band of frontal convection stretching from West
   Virginia/western Virginia to the Florida Peninsula early. 
   Limited/local severe potential will be ongoing, with a gradual,
   modest increase in threat expected through late morning/early
   afternoon from eastern North Carolina northward into the Mid
   Atlantic region as at least 500 J/kg mixed-layer CAPE spreads
   northward across the coastal Mid-Atlantic/Chesapeake Bay region.  

   Very strong flow through a deep layer suggests potential for
   damaging winds, where stronger storms can transport momentum
   downward.  Meanwhile, favorably increasing/veering flow with height
   through the lower troposphere will also support potential for
   low-level rotation -- and thus a couple of tornadoes appear possible
   where sustained supercell storms can evolve.  

   By mid evening, convection will have largely moved off the Mid
   Atlantic Coast, while some severe risk lingers over southern New
   England -- possibly into the overnight hours.

   ...Central Florida...
   As the cold front shifts southeastward across Florida through the
   day, a band of showers and thunderstorms is likewise forecast to
   cross the Peninsula.  Storms will likely be ongoing within this
   frontal band at the start of the period, but modest CAPE expected
   ahead of the front suggests that most of the convection should
   remain sub-severe.  Still, with amply strong (around 50 kt)
   mid-level westerly flow atop the frontal zone, gusty/locally
   damaging winds may occur with one or two of the strongest storms,
   before convection weakens into the afternoon hours in the wake of
   the passage of a weak vort max.

   ..Goss/Moore.. 11/30/2020

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