Mesoscale Discussion 0099
NWS Storm Prediction Center Norman OK
0822 PM CST Sat Jan 21 2017
Areas affected...Portions of northern Louisiana...southern
Arkansas...and central/southern Mississippi
Concerning...Tornado Watch 17...18...
Valid 220222Z - 220415Z
The severe weather threat for Tornado Watch 17, 18 continues.
SUMMARY...Severe thunderstorms will continue to develop into Watch
18 over the next hour. Across northern portions of the watch, the
main severe hazard will likely transition to damaging winds (with a
tornado or two possible). Farther southeast in Mississippi, a
greater tornado/large-hail potential will exist, with a strong
tornado possible.
DISCUSSION...In response to increasing warm advection related to the
low-level jet, severe thunderstorms near the LA/AR border have begun
to grow upscale into a broken band, with embedded mesocyclones still
noted. This evolution should continue as the storms progress into
Watch 18, resulting in damaging winds likely becoming the dominant
threat across northern portions of the watch. A tornado or two will
still be possible, however, considering the amplifying low-level
flow and notable veering with height of 0-3-km winds.
Farther southeast over south-central Mississippi, dew points in the
lower 60s will favor slightly greater surface-based buoyancy. KDGX
VWP data suggest around 250-300 m2/s2 of storm-relative helicity is
present for low-level mesocyclone organization. With increasing
semi-discrete convection over the next several hours, the tornado
potential should rise accordingly, and a strong tornado (primarily
closer to the MS/AL border) cannot be ruled out.
..Picca.. 01/22/2017
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...MOB...MEG...JAN...LIX...LZK...SHV...
LAT...LON 32099280 32719344 33029341 33969225 33749036 32938851
32258847 31648881 31278954 31399119 31489220 32099280
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