SPC MD 1561

MD 1561 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF EASTERN/SOUTHERN GA AND SC

Mesoscale Discussion 1561
NWS Storm Prediction Center Norman OK
0214 PM CDT Wed Aug 23 2017

Areas affected...Portions of eastern/southern GA and SC

Concerning...Severe potential...Watch unlikely 

Valid 231914Z - 232045Z

Probability of Watch Issuance...5 percent

SUMMARY...There is a very small threat for localized wind damage
associated with storms this afternoon. Watch issuance will not be
necessary.

DISCUSSION...A diffuse cold front is located just west of the
discussion area. Along and ahead of this boundary, flow throughout
the depth of the troposphere is very weak (e.g., around 10 knots at
500 mb over most of the area), thus, organized storm modes are not
expected. However, ahead of the front, moderate buoyancy is in place
with limited capping owing to diabatic heating of a moist boundary
layer characterized by lower to middle 70s surface dewpoints.
Isolated to widely scattered thunderstorm development will continue
through the afternoon, focused along the Atlantic sea breeze, the
front, and other weak pre-frontal convergence axes. Most storms that
develop are unlikely to be severe, but there is a small chance that
a couple of storms could briefly produce wind damage with wet
microbursts, given DCAPE upwards of 1000-1250 J/kg. Poor mid-level
lapse rates will greatly temper convective-scale vertical
accelerations, greatly limiting the severe risk amidst weak deep
shear.

..Cohen/Clark/Coniglio/Darrow.. 08/23/2017

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...ILM...CHS...CAE...JAX...FFC...

LAT...LON   31698105 31108135 31018194 31288251 32078275 32978229
            33768135 33698029 33367926 32767978 32238071 31698105 

SPC MD 1560

MD 1560 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF SOUTHEAST VA...EASTERN AND CENTRAL NC...AND NORTHERN SC

Mesoscale Discussion 1560
NWS Storm Prediction Center Norman OK
1223 PM CDT Wed Aug 23 2017

Areas affected...Portions of southeast VA...eastern and central
NC...and northern SC

Concerning...Severe potential...Watch unlikely 

Valid 231723Z - 232000Z

Probability of Watch Issuance...20 percent

SUMMARY...There will be an isolated damaging-wind threat with storms
this afternoon.  While present indications are that Watch issuance
will be unlikely, convective and environmental trends will continue
to be monitored.

DISCUSSION...Thunderstorm development and intensification is
forecast to continue across parts of the mid-Atlantic through the
afternoon hours, with generally limited storm organization. A
mid-level trough is progressing eastward across southern New England
and the mid-Atlantic, with an associated cold front moving
southeastward across the discussion area. Most of the favorable deep
shear associated with the mid-level trough is displaced to the north
of the strongest pre-frontal buoyancy. However, there is a small
area across southeast VA and parts of northern NC where effective
shear around 25-35 kt coincides with adequate buoyancy for somewhat
organized storm structures -- enhanced by elongated low-level
hodographs over the shallow frontal surface. This may be the focused
zone for the most robust convection and most prominent damaging-wind
risk.

Otherwise, farther south across the Carolinas where deep shear will
remain weaker, the very moist boundary layer (e.g., surface
dewpoints in the middle 70s) supporting 1500-3000 J/kg of MLCAPE,
with minimal MLCIN should lead to fairly widespread storm
development with an isolated potential for wet microbursts capable
of producing wind damage. Convection-allowing model guidance also
indicates that storms may develop along a sea-breeze circulation
near the Atlantic coast, and other storms may develop east of the
cold front associated with boundary-layer circulations and a
pre-frontal trough. These storms may also be associated with
isolated damaging winds.

The overall lack of overlap of stronger buoyancy and stronger
vertical wind shear, and presence of poor mid-level lapse rates,
will tend to minimize the overall severe risk.

..Cohen/Clark/Coniglio/Darrow.. 08/23/2017

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...AKQ...MHX...RAH...ILM...RNK...CAE...GSP...

LAT...LON   34217769 33697961 34308115 35098119 36577896 37177782
            37387674 37317603 37127569 36367557 35267600 34217769