SPC MD 1641



MD 1641 CONCERNING SEVERE POTENTIAL…WATCH POSSIBLE FOR PORTIONS OF COASTAL NC/SC

MD 1641 Image

Mesoscale Discussion 1641
NWS Storm Prediction Center Norman OK
1116 PM CST Mon Nov 12 2018

Areas affected...Portions of coastal NC/SC

Concerning...Severe potential...Watch possible 

Valid 130516Z - 130745Z

Probability of Watch Issuance...60 percent

SUMMARY...Thunderstorms will move northeastward across parts of the
coastal Carolinas overnight, with both an isolated tornado and
strong to locally damaging wind threat. Watch issuance is possible.

DISCUSSION...A strong southerly low-level jet (around 40-50 kt) has
developed over the eastern Carolinas per recent VWPs from KLTX and
KMHX. Warm air advection attendant to the LLJ has encouraged recent
thunderstorm development along a surface front very near the coast
of SC as of 05Z. A weak surface low is expected to develop
northeastward along this boundary overnight, and continued warming
and moistening of the low levels will likely occur across coastal
NC/SC. Forecast soundings from latest RAP/HRRR guidance indicate
there will be some threat for surface-based thunderstorms where
dewpoints can reach into the upper 60s to around 70. Strong speed
shear mainly in the 0-1 km layer will contribute to large effective
SRH values across this region, potentially in excess of 300 m2/s2.
Even though instability will remain weak owing to poor lapse rates
through the column, MLCAPE up to 1000 J/kg will likely be sufficient
for surface-based thunderstorms along/near the coast. Effective bulk
shear values of 45-55 kt will support supercells, and the strong
low-level shear suggests isolated tornadoes may occur with these
storms. Strong to damaging straight-line winds will also be a
possibility with any cluster that may evolve. Short-term guidance
suggests an appreciable inland severe threat may develop near the
coastal NC/SC border region by about 07Z, and a watch may eventually
be needed.

..Gleason/Thompson.. 11/13/2018

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

ATTN...WFO...MHX...ILM...

LAT...LON   33287880 33677920 33897923 34257874 34557823 35837665
            36047602 36067562 35667542 35207548 34997608 34547650
            33907789 33287880 

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