- Day Three
acus03 kwns 210813
Storm Prediction Center ac 210812
Day 3 convective outlook
National Weather Service Storm Prediction Center Norman OK
0212 am CST Thu Nov 21 2019
Valid 231200z - 241200z
..no severe thunderstorm areas forecast...
isolated to widely scattered thunderstorms are expected over a part
of the southeast states Saturday. Threat for severe weather appears
low at this time.
A progressive southern-stream shortwave trough will move through the
southeast states accompanied by a cold front Saturday. Weak
cyclogenesis is expected over the Tennessee Valley early in the period, and
this low is forecast to weaken as it moves northeast into the
central Appalachians. Secondary cyclogenesis is forecast across NC
and Virginia overnight as a strong vorticity maximum moves into the base
of the upper trough and interacts with the baroclinic zone.
Partially modified Gulf air with surface dewpoints generally in the
low to mid 60s f will advect into the Gulf Coast states Saturday.
This will result in some destabilization, but instability will
remain very marginal (mucape below 500 j/kg) due to widespread
clouds and poor low to mid-level lapse rates. It is likely that
scattered showers with embedded thunderstorms will be ongoing along
the warm conveyor along and just ahead of the cold front, and this
activity will advance east during the day. Thunderstorm coverage
will probably diminish with eastward extent due to more limited
moisture and instability. However, a separate area of thunderstorms
may develop over the coastal Carolinas late Saturday night as the
front intercepts Richer low-level moisture. While vertical shear
will be more than adequate to support storm organization, the very
weak thermodynamic environment should remain a limiting factor for