Valid 051300Z – 061200Z
…THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS EASTERN NC…
Several brief tornadoes remain possible across eastern North
Carolina through tonight in association with Hurricane Dorian.
…Eastern NC vicinity…
Major changes to upgrade and expand tornado probabilities.
Tornadic supercells have been observed this morning off the
Wilmington 88-D with several debris signatures near the NC/SC border
area. Numerous supercells should continue to be embedded within
multiple arcing outer bands of Hurricane Dorian. These bands should
gradually shift north through the day with a persistent threat for
several brief tornadoes.
Latest guidance has trended more aggressive with destabilization
across the coastal plain of NC where low to mid 70s surface dew
points are common at present. Only weak boundary-layer heating north
of the ongoing convective bands will be needed to boost MLCAPE to
1000-1500 J/kg. This should compensate for comparatively smaller
low-level hodographs with northern extent in northeast NC/southeast
VA and could support a midday/early afternoon uptick in tornado
potential north of the coastal bands. The tornado threat tonight
will become confined to the Outer Banks and northeast NC region as
Dorian continues to progress northeastward.
In the wake of scattered elevated thunderstorms spreading north this
morning, a plume of MLCAPE from 500-1000 J/kg is expected at peak
heating. An approaching shortwave trough off the northern CA coast
should support late afternoon thunderstorm development over the
Cascades. A deeply mixed and steep low/mid-level lapse rate
environment coupled with 30-40 kt effective shear should support
isolated severe wind and hail.
Isolated severe hail will be possible with an elevated cluster this
morning and with any elevated convection that can redevelop this
evening. Ongoing elevated storms across northwest to north-central
MN in association with a ribbon of 700-mb warm advection attendant
to a leading shortwave impulse should subside as the impulse decays
today. However, a quick-moving upstream impulse over southwest SK
will aid in mid-level height falls and DCVA overspreading northeast
MN and northern WI towards evening. Modest elevated buoyancy and
robust speed shear through the cloud-bearing layer could support a
couple rotating updrafts capable of marginally severe hail.