Valid 022000Z – 031200Z
…THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE MID
Scattered severe thunderstorms with large hail, a couple tornadoes,
and damaging winds are anticipated across the Mid-South, after about
5 PM CST through tonight.
Only modest changes to previous forecast have been made this update,
primarily to expand the MRGL farther south across southern MS to
account for storms the are expected to spread into this region late
tonight posing a marginal risk for mainly strong wind gusts.
Otherwise, forecast appears on track. A capping inversion should
delay thunderstorm initiation until early evening along a cold front
from southeast MO into northern AR as deeper ascent attending a
shortwave trough currently moving through KS interacts with this
boundary and a secondary branch of the southwesterly low-level jet
increases. The shear/instability parameter space is more than
sufficient for supercells capable of very large hail and a couple of
tornadoes, before storms evolve into clusters tonight. Considered
upgrade to enhanced risk, but given expected initiation near sunset
when the boundary layer will be stabilizing, the window of
opportunity for a more significant severe event appears relatively
.PREV DISCUSSION… /ISSUED 1025 AM CST Mon Mar 02 2020/
…Mid-South to northeast TX…
Primary change is to expand Marginal and Slight Risks northward and
eastward with above-average confidence in scattered severe
thunderstorm coverage being realized.
At the surface, a weak cyclone will move northeast along a
baroclinic zone from east-central OK across the OH Valley tonight.
Low-level moistening continues to the south of the front, and 60-63
F surface dew points will spread northeast across most of the
Mid-South by evening. This moistening will occur beneath the eastern
extent of a plume of steep mid-level lapse rates overspreading from
KS/MO/OK. The base of the elevated mixed layer will be warm enough
to cap the boundary layer until about early evening.
Sustained thunderstorm development is expected near the front where
low-level convergence will be relatively stronger, just ahead of the
surface low across the northeast AR/southeast MO vicinity. MLCAPE
of 1000-1500 J/kg, effective bulk shear around 40 kt, mid-level
lapse rates in excess of 8 C/km, and elongated/straight-line mid to
upper-level hodographs will favor multiple splitting supercells
capable of producing large hail, some of which may be significant. A
modest increase in low-level shear this evening could support a
tornadic storm or two as well. Storm-scale consolidation and the
impinging of 50-kt westerlies at 700 mb may yield upscale growth
into a modest-sized MCS across parts of TN and southern KY with the
damaging wind threat peaking between 03-07Z.
Farther southwest, isolated thunderstorm development is also
possible this evening along the front into northeast TX. However, a
shallow moist boundary layer and widespread high clouds cast some
doubt on diurnal storm formation. Assuming storms form this
evening, isolated large hail and strong wind gusts will be possible.