|Mesoscale Discussion 818|
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Mesoscale Discussion 0818
NWS Storm Prediction Center Norman OK
0350 PM CDT Tue May 23 2017
Areas affected...Portions of the FL Panhandle...southern and
southeastern GA...and coastal SC/NC
Concerning...Tornado Watch 257...258...
Valid 232050Z - 232215Z
The severe weather threat for Tornado Watch 257, 258 continues.
SUMMARY...An isolated tornado and damaging wind threat continues
across Tornado Watches 257/258. The prospect of downstream watch
issuance into coastal NC is uncertain.
DISCUSSION...Primary near-term severe threat will remain focused
with a cluster of thunderstorms across southeastern GA in
association with a strong 40+ kt southwesterly low-level jet. The
airmass downstream of this cluster into coastal SC remains weakly
unstable, with MLCAPE of 500-1000 J/kg present. Recent VWP from KCLX
shows strongly veering winds with height supporting around 50 kt of
0-6 km shear, and RAP Mesoanalysis estimates 200-300 m2/s2 of 0-1 km
SRH is present across this region. This will support continued
updraft organization and low-level rotation with the strongest
updrafts, and isolated tornadoes/damaging winds will continue to be
possible across southeastern GA into parts of coastal SC for at
least the next several hours.
Behind the ongoing convective cluster in southeastern GA, low-level
winds have veered more to southwesterly in southern GA and much of
the FL Panhandle to the south of a weak front evident in 20Z surface
observations. This has reduced 0-1 km SRH per latest TLH VWP and RAP
Mesoanalysis estimates. While a brief tornado cannot be ruled out in
this region, it appears the overall severe threat is diminishing
across Tornado Watch 257. If current radar trends continue, then
Tornado Watch 257 will be allowed to expire at 22Z as scheduled.
Farther north across coastal NC, some increase in an isolated
tornado/damaging wind threat should occur through the early evening
as the low-level jet overspreads this area. The prospect for surface
based-convection and related severe threat will likely remain
confined to a small part of coastal NC, and the prospect for a
downstream watch into this region remains unclear.
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 30258540 30678315 31468296 32658178 33977979 34737834
34707779 34427729 33937781 33077913 32328032 31688102
30748141 30368205 30068409 30008496 30258540
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