SPC AC 011620
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1120 AM CDT Sun Aug 01 2021
Valid 011630Z - 021200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PARTS OF THE
CAROLINAS AND NY/PA...
Scattered damaging winds and a tornado or two are most likely across
portions of the Carolinas into early evening. Scattered damaging
winds are also possible over parts of New York and Pennsylvania
through early evening.
A few supercells have evolved into a small cluster along the surface
front across northeast NC. Additional convective development is
expected farther southwest near the surface cyclone across central
NC. Air mass ahead of the front/cyclone continues to destabilize in
the presence of mid to upper 70s surface dew points. While low-level
SRH should remain modest, slightly backed surface winds across far
eastern NC may support the threat for a tornado or two. The primary
hazard will likely be scattered damaging winds as the upstream
convection develops and evolves into an eastward-moving cluster
across eastern NC through this afternoon.
Lower-topped thunderstorms have developed along and just ahead of an
eastward-progressing cold front in the lee of the Lower Great Lakes.
More pronounced boundary-layer heating is underway across western to
northeast PA into southeast/east-central NY, which should aid in
some intensification of convection this afternoon. However,
boundary-layer temperatures and dew points will be seasonally subpar
with the bulk of destabilization occurring through steepening of
mid-level lapse rates with approach of the shortwave trough. In
addition, lower-level flow will remain relatively modest with faster
mid-level flow largely confined to the upper portion of the weak
buoyancy profile. As such, convection may struggle to become
substantially deep and organized, which may result in only sporadic
bouts of damaging winds and isolated marginally severe hail.
Scattered thunderstorms are expected along a trailing cold front
that will slowly slide south across the region this afternoon. Weak
deep-layer shear but large buoyancy will favor pulse to loosely
organized multicells. Wet microbursts capable of producing locally
damaging wind gusts will be the main hazard.
In what is otherwise a weak meridional flow pattern across the West,
a pair of MCVs, one over southeast NV and the other near the
OR/ID/WA border area, may help focus weakly organized severe
potential this afternoon. Relatively high PW values along with steep
low-level lapse rates will support a threat for microbursts capable
of isolated severe gusts.
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