SPC 1730Z Day 2 Outlook

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1059 AM CST Sun Nov 29 2020

Valid 301200Z - 011200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
EASTERN NC INTO FAR SOUTHEAST VA...

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

...Synopsis...
A closed mid/upper low is expected to develop over the
Midwest/central Appalachians on Monday as a large-scale upper trough
pivots eastward across the eastern U.S. At the surface, low pressure
over WV will lift northward across PA/NY through Monday evening. A
trailing cold front is expected to extend from western NC southward
through eastern GA and northern FL at the beginning of the period.
Meanwhile, a warm front will lift northward across the mid-Atlantic
through the afternoon, extending from eastern PA into CT and
southern MA by 21z. The cold front will quickly push
eastward/southeast across NC/SC and central FL during the daytime
hours, moving offshore the Mid-Atlantic and southeastern U.S. coast
(except in FL) by 21-00z, and offshore the New England coast during
the overnight hours. 

Dewpoints in the upper 50s to mid 60s F will reside across the warm
sector, but instability will be limited due to ongoing convection
and cloud cover, especially with northward extent. Still, at least a
few hundred J/kg MLCAPE is forecast from FL northward toward the
southern New England coast.

...Coastal NC into far Southeast VA...

A Slight risk has been maintained with this update across parts of
eastern NC into far southeast VA. The most favorable conditions for
a mix of semi-discrete supercells and line segments will exist
across this area during the morning and early afternoon hours.
Backed low level flow to the southeast of the surface low over
northern VA will result in enlarged low level hodographs. Strong
south/southwesterly shear also will reside over the region in
conjunction with MLCAPE values as high as 750 J/kg. Fast storm
motion and strong low level winds will favor mainly a locally
damaging wind threat, though a couple of tornadoes will be possible.


...Chesapeake Bay vicinity to Coastal Southern New England...

Instability will quickly diminish with northward extent as deeper
boundary layer moisture lessens and cooler surface temperatures are
forecast. Nevertheless, a couple hundred J/kg MLCAPE is evident in
forecast soundings in conjunction with strong southerly shear.
Forcing for ascent will also be maximized across the area, and
low-topped bowing line segments will be possible in the high-shear,
low-CAPE environment. Locally damaging gusts will be the main
concern with this activity. A shallow low level inversion will
likely limit tornado activity, however, this limitation could be
overcome near the surface low and along the warm front, and a
tornado or two can not be ruled out. 

...Central FL...

Instability will be maximized over the FL peninsula where deeper low
level moisture will be present ahead of the cold front. However, low
level convergence will be weak as deep layer flow becomes more
parallel to boundary with the surface low and trough ejecting well
to the northeast. Nevertheless, forecast soundings indicate adequate
instability and shear to support at least a narrow corridor of
low-end severe potential before a more subsident airmass moves into
the area. The strongest cells during the morning hours could produce
locally strong gusts.

..Leitman.. 11/29/2020

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