SPC AC 220819
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0219 AM CST Thu Feb 22 2018
Valid 241200Z - 251200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM A PORTION OF
EAST TEXAS INTO THE LOWER MISSISSIPPI...TENNESSEE AND OHIO
VALLEYS...
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM A PORTION
OF THE SOUTHERN PLAINS THROUGH THE OHIO VALLEY AND SOUTHEAST
STATES...
...SUMMARY...
Strong to severe storms will be possible Saturday from a portion of
northeast Texas through the lower Mississippi, Tennessee and Ohio
Valleys.
...Northeast TX into the lower Mississippi Tennessee and Ohio
Valleys...
A significant shortwave trough will eject northeast through the
central Plains and middle to upper MS Valley region Saturday and
Saturday night while taking on a negative tilt. In response to
forcing accompanying this feature, a surface low initially over the
southern Plains will deepen as it develops northeast through the
middle MS Valley, eventually reaching the Great Lakes toward the end
of the period. Warm front extending east from the surface low will
move northward, reaching the OH Valley Saturday night. A cold front
initially across west TX will advance through the Southern Plains
and middle to lower MS Valley during the day reaching the OH and TN
Valleys Saturday night. A strengthening low-level jet resulting from
the deepening cyclone will transport richer gulf moisture northward
with low 60s F dewpoints as far as the OH Valley and mid to upper
60s from east TX to the lower MS Valley. However, instability will
probably remain marginal due to widespread clouds and modest lapse
rates with MLCAPE likely to remain below 1000 J/kg over most of the
warm sector.
A forced line of potentially strong to severe storms should evolve
in vicinity of cold front initially over north central or northeast
TX into southeast OK during the day. Activity will subsequently move
into the lower MS, TN and OH Valley regions as the low-level jet
strengthens to 60+ kt and shifts northeast through moistening warm
sector. Vertical shear and overall character of wind profiles will
be more than adequate for organized severe storms, with potential
for LEWP, bowing segments and a few embedded supercells capable of
damaging wind and a few tornadoes. An upgrade to higher
probabilities might be needed in later outlooks once uncertainties
regarding the thermodynamic environment have been mitigated.
..Dial.. 02/22/2018
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