Valid 112000Z – 121200Z
…THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR EASTERN AND
SOUTHERN PARTS OF ALABAMA…FAR WESTERN GEORGIA…
Scattered to potentially numerous damaging gusts are forecast for
eastern Alabama and western Georgia this afternoon. The greatest
threat for tornadoes will accompany the squall line from Alabama
northeast into Georgia and possibly into the western Carolinas
Substantial changes to the prior outlook include the following:
1) Removal of severe probabilities west of the extensive north-south
squall line from the OH Valley southward to Mobile Bay.
2) A slight reduction in tornado probabilities over AL from
10-percent significant to 5-percent due to the realizing of a
less-favorable convective mode (i.e., squall line) for tornado
potential. Nonetheless, a tornado risk will likely accompany any
stronger/more persistent mesovortex managing to develop within the
3) Have included the western Carolinas into southern VA into the
categorical Slight Risk (wind and tornado probability equivalent).
Recent forecast model soundings indicate upwards of 500 J/kg MLCAPE
may develop immediately ahead of the squall line as one or more LEWP
structures rapidly move northeast this evening from GA into the
Carolinas and later VA. Very intense low-level flow coupled with
weak potential instability will conditionally support a risk for
damaging gusts and perhaps one or two brief tornadoes.
.PREV DISCUSSION… /ISSUED 1028 AM CST Sat Jan 11 2020/
A fast-moving squall line is tracking eastward across the OH/TN
Valleys and central Gulf Coast states today, producing numerous
reports of wind damage over the past few hours. The northern end of
the line over IN/OH/KY is moving into a progressively more
dry/stable air mass, with general weakening noted in
satellite/radar/lightning data. Despite the weakening, locally
damaging wind gusts will remain possible for the next few hours
along the leading edge of the line of convection.
The intense squall line extends southward across middle TN into
northwest AL and eastern MS. The air mass ahead of the line is
modestly unstable with dewpoints in the low/mid 60s. Little daytime
heating is expected, but afternoon MLCAPE values as high as 1000
J/kg may be realized over central AL later today. Given the
extremely strong wind fields, this parameter space will remain
conducive for damaging winds and QLCS mesovortices along the squall
line. The warm sector continues to show a little capping per recent
soundings in northern AL. If the capping erodes, the potential for
a few discrete supercells ahead of the line would increase, along
with a potential for a strong tornado or two.
…Carolinas into PA/NJ…
The convective line will likely maintain some character through much
of the night, with occasional gusty/damaging wind reports all the
way to the Atlantic coast.