SPC AC 190727
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0227 AM CDT Sat Oct 19 2019
Valid 211200Z - 221200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS MONDAY ACROSS
PARTS OF THE LOWER MISSISSIPPI VALLEY...
...SUMMARY...
Severe thunderstorms are possible Monday across portions of the
lower Mississippi Valley, into portions of the lower Ohio Valley,
posing a risk for damaging wind gusts and perhaps a few tornadoes.
...Discussion...
Rather amplified large-scale troughing over the interior U.S. may
take on more of a negative tilt while progressing across the
Mississippi Valley during this period. Smaller-scale embedded
perturbations/developments remain more unclear due to sizable spread
within model output, but it does appear that there may be
substantive further deepening of the primary associated
lower/mid-tropospheric cyclone. The center of this feature is
expected to migrate from the mid Missouri Valley into the Upper
Midwest Monday through Monday night, with an occluding surface front
surging east of the Mississippi Valley toward the Appalachians.
Lapse rates within much of the moistening portion of the warm sector
of the cyclone are generally forecast to remain weak, which may
limit CAPE to around 500-1000 J/kg within a pre-frontal plume across
the lower Mississippi Valley into the lower Ohio Valley.
South to southwesterly lower/mid tropospheric flow may include 50-70
kt at 850 mb, and 70-90+ kt at 500 mb, but there may be a tendency
for the strongest deep-layer mean wind fields to shift north of the
destabilizing warm sector early in the period.
Still, there appears potential for the environment to become
conducive to the development of a combination of one or more broken
lines of storms and discrete supercells, particularly during the day
Monday across Louisiana, Mississippi, and adjacent portions of
southeast Arkansas and western Alabama, into portions of middle
Tennessee, which probably will be accompanied by a risk for damaging
winds and a few tornadoes.