Pre-frontal convective band will
likely begin overspreading the
NC
mountains circa 12Z Thursday.
Buoyancy is forecast to be quite
limited during this time, but there may well be a severe
downburst
threat during this time, depending upon the strength of the cold
pool produced in the stronger
CAPE environment
upstream. A consensus
of model guidance continues to depict weakening of low level forcing
over the mountains as the terrain disrupts low level
flow patterns.
However, mid and upper levels will remain strongly forced. If
anything, this scenario may yield more of a broken convective band,
with embedded discrete cellular modes...which is kind of hinted at
in the latest
convection-allowing models. Low level
shear
parameters, including
storm relative helicity will be quite
impressive, so the magnitude of the severe threat will hinge largely
upon the amount of
instability that is realized...which will be
largely dictated by timing of
convection with respect to the
diurnal
heating cycle. Considering the expected timing of
convection
sweeping across the western half of the area 12-15Z, and the eastern
half 15-18Z, the eastern third or so of the forecast area is
expected to see the greatest threat of severe storms, as reflected
in the Moderate Risk from the Day 2
SPC Convective
Outlook. All
modes of severe weather will be possible, especially in and near the
Moderate Risk area, with a strong
tornado or two possible in
association with supercellular storm structures. Again, timing will
be (almost) everything: earlier timing will
likely result in a
diminished threat, later timing would
likely yield a significant
severe thunderstorm outbreak for our area.
