SPC AC 100422
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1122 PM CDT Fri Apr 09 2021
Valid 111200Z - 121200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF
Isolated strong to severe thunderstorms are possible on Sunday
across parts of the eastern Florida Panhandle and the Florida
An upper low over the Midwest and its attendant trough extending
southeastward through the southeast U.S. will pivot northeast on
Sunday. The upper low will become oriented over the lower Great
Lakes by Monday morning, while the associated trough extends along
the Mid-Atlantic coast and offshore the southeastern U.S. coast.
This should maintain moderate west/southwesterly flow from the
Mid-Atlantic/central Appalachians southward through Florida for much
of the period. A surface low stacked beneath the upper low over the
Great Lakes will not move much, but instead weaken through the
period. A cold front will extend from western PA along the
Appalachians and into southeast AL and then just offshore from
south-central LA. While the southern most segment of the front will
stall along the central Gulf coast, much of the front should shift
eastward, moving offshore the Mid-Atlantic cost and into northern
Florida by Monday morning.
A mature MCS/QLCS is forecast to be ongoing across parts of northern
Florida Sunday morning. Some severe threat could persist with this
system as it tracks southeastward across the Florida Peninsula
through the day.
Most guidance has a mature MCS/QLCS over northern FL at the
beginning of the period, and the evolution of the severe threat on
Sunday will depend on where exactly this activity is located during
the morning, and specifically how far south any outflow may develop
early in the period. This could impact how much CINH exists and how
much recovery can occur through peak heating. Nevertheless, mid to
upper 60s dewpoints will be in place, and at least weak
destabilization should occur amid 35-45 kt effective shear. This
should be sufficient to support at least a low-end threat for
locally damaging gusts and hail.
...Delmarva into parts of eastern PA...
Modest low level moisture is expected to extend northward into the
Chesapeake vicinity, with mid 50s to near 60 F surface dewpoints
forecast. Stronger forcing closer to the surface and upper lows,
along with a better-defined cold front surging eastward should
provide focus of isolated thunderstorm development during the
afternoon. Instability is currently forecast to remain weak,
generally less than 1000 J/kg, along with modest vertical shear.
Midlevel lapse rates near 7 C/km and a deeply mixed boundary layer
resulting in steep low level lapse rates also will overspread the
region. Some locally gusty winds or small hail could accompany any
stronger cells. However, weak low level winds and overall modest
thermodynamic/kinematic environment will preclude severe
probabilities at this time.
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