SPC 1300Z Day 1 Outlook

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0700 AM CST Wed Nov 25 2020

Valid 251300Z - 261200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE LOWER
MISSISSIPPI VALLEY/TENNESSEE VALLEY INTO THE OHIO VALLEY...

...SUMMARY...
Isolated strong to severe thunderstorms are possible today from the
lower Mississippi Valley into the Tennessee Valley and lower Ohio
Valley. Locally damaging winds should be the main threat, although a
tornado or two could also occur.

...Lower Ohio Valley/Tennessee Valley/Lower Mississippi Valley...
A shortwave trough/speed max aloft over the Ozarks will steadily
progress east-northeastward today and tonight over the Ohio and
Tennessee Valleys, with a corresponding surface wave moving
northeast across Missouri/Illinois/Indiana and Ohio through evening.
Ahead of an eastward-moving cold front, showers are prevalent early
this morning across the lower Ohio Valley and western Tennessee,
with thunderstorms associated with a semi-organized convective line
across Mississippi into central/southern Louisiana.

Initially, an isolated severe risk should persist early today with
the aforementioned convective line as it continues across
Mississippi/southern Louisiana into Alabama, with damaging winds a
possibility along with a quasi-linear-related localized tornado
risk.

Other strong/locally severe low-topped thunderstorms could develop
this afternoon near the surface low, including far eastern portions
of Missouri/western Kentucky and southern Illinois. However, the
degree and likelihood of such a severe risk is not certain given a
relatively limited opportunity/potential for destabilization, but a
damaging wind/localized tornado risk could occur.

Farther south, in the wake of the early day convection, there are
some indications that storms could redevelop near the cold front
late this afternoon and evening across the Tennessee Valley
including northern Alabama and possibly nearby portions of middle
Tennessee and/or eastern Mississippi. It is possible if not probable
that guidance such as the RAP/NAM are too quick/aggressive with air
mass recovery and destabilization into late afternoon/early evening.
However, should modest/adequate destabilization occur, given that
the region would be within the entrance region of a strong
south-southwesterly low-level jet, wind profiles would be favorable
supercells potentially including some tornado/damaging wind risk.
Portions of this region could warrant a categorical Slight Risk
upgrade if confidence increases in air mass destabilization in the
wake of early day convection/cloud cover.

..Guyer/Broyles.. 11/25/2020

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