Mesoscale Discussion 0869
NWS Storm Prediction Center Norman OK
0316 PM CDT Sat May 27 2017
Areas affected...Portions of central/southern VA and northern NC
Concerning...Severe potential...Watch possible
Valid 272016Z - 272145Z
Probability of Watch Issuance...40 percent
SUMMARY...An isolated severe risk may develop late this afternoon
and continue into this evening. Large hail and strong to locally
damaging wind gusts would be the main threats. Watch issuance is
possible.
DISCUSSION...20Z surface analysis shows a remnant front stalled
across northern into southeastern VA. Strong diurnal heating of a
moist low-level airmass has resulted in weak to locally moderate
instability, and MLCAPE generally ranges from 500-1500 J/kg along
and south of the front. Water vapor satellite imagery shows a
low-amplitude, convectively enhanced shortwave trough moving over
the central Appalachians as of 20Z. Modifying the 18Z sounding from
RNK for current observations shows the mid-level inversion centered
on 700 mb is almost completely eroded, and convection has begun to
recently increase in coverage and intensity along/near the higher
terrain of central/southern VA. 0-6 km bulk shear values of 40-50 kt
per latest RAP Mesoanalysis and FCX VWP will easily support
supercells. Isolated large hail and strong to locally damaging winds
will be possible with the strengthening convection across this
region. Recent operational HRRR runs suggest convection may attempt
to grow upscale into one or more line segments through this evening,
which could enhance the damaging wind threat. Watch issuance is
possible over the next several hours depending on radar trends.
..Gleason/Hart.. 05/27/2017
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...AKQ...LWX...RAH...RNK...
LAT...LON 36818010 38427919 38697859 38317744 37747702 36497709
36147765 36067881 36077963 36358004 36818010
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