Valid 241200Z – 251200Z
…THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER SOUTHEAST
MISSOURI…EASTERN ARKANSAS…WESTERN TENNESSEE AND NORTHERN
Isolated marginally severe storms are possible from southern
Missouri into northern Mississippi during the afternoon and early
…Synopsis and Discussion…
A shortwave trough and surface low will move from OK toward the
lower OH Valley during the day, with dryline trailing south across
AR and eastern TX. Ahead of this front, a relatively cool air mass
will be in place over the Southeast due to high pressure, but
persistent south winds will bring mid 50s F dewpoints into AR and
northern MS, with low 60s F over LA and southern MS.
During the day, heating and boundary-layer mixing will establish a
low-level lapse rate plume near the dryline, nosing into central AR
by late afternoon. This will help steepen lapse rates, as
temperatures aloft also cool. Forecast soundings indicate 500-750
J/kg MUCAPE developing, but with midlevel subsidence and drying as
the shortwave trough passes quickly east. Still, an arcing, broken
line of thunderstorms is expected from southern MO across eastern AR
and into northern MS from late afternoon through evening. While
strong deep-layer shear will exist, updrafts will encounter a cool
air mass as they advance east, along with the midlevel subsidence.
The NAM appears less favorable than the RAP, which shows better
instability. Given strong shear and likelihood of scattered storms,
low severe probabilities have been introduced. Marginal hail, wind,
or a brief/weak tornado are all possible.
Elsewhere, 40 kt southwesterly 850 mb winds will bring mid 60s F
dewpoints across the FL Panhandle and into far southwest GA by 12Z
Tue, well ahead of the cold front. Within this regime, scattered
storms are likely with a few hundred J/kg MUCAPE present. At this
time, it appears the boundary-layer may be too stable to support any
severe threat. However, this area will experience moderate low-level
shear, and will be monitored in subsequent forecast cycles.