Day 1 Severe Weather Outlook

Valid 301200Z – 011200Z


Severe thunderstorms will be possible this afternoon and evening
from the Arklatex area eastward to southeast Arkansas, northwest
Mississippi and southwest Tennessee. Wind damage, hail and a few
tornadoes will be the main hazards.

…Arklatex/Lower to Mid Mississippi Valley…
An upper-level low will move eastward into the mid Missouri Valley
today as powerful 100 to 120 kt mid-level jet rounds the base of the
associated upper-level trough. At the surface, a moist airmass ahead
of the system will advect northeastward into the lower to mid
Mississippi Valley. Surface dewpoints should increase into the 60s F
across much of the lower to mid Mississippi Valley ahead of a cold
front. As instability increases around midday, thunderstorms are
forecast to develop along the front from east Texas northeastward
into central Arkansas. This convection should spread
east-northeastward into the lower to mid Mississippi Valley during
the mid to late afternoon.

RAP forecast soundings along the moist axis in the 21Z to 00Z
timeframe from Monroe, Louisiana to south of Memphis, Tennessee
increase MLCAPE values to near 1500 J/kg and have 0-6 km shear in
the 60 to 70 kt range. In addition, 0-3 km storm relative helicity
values are forecast to reach the 250 to 350 m2/s2 range. This
suggests that the environment will support supercell development
with a few tornadoes possible. An isolated significant tornado can
not be ruled out along the corridor with the strongest low-level
shear. The tornado threat should depend upon how discrete cells
remain as convective coverage increases during the afternoon. Some
uncertainty exists concerning the tornado threat due to a
veer-back-veer signature evident on many forecast soundings. The
axis of greatest severe threat should be from north-central
Louisiana northeastward into western Tennessee. Supercells along
this corridor should also be capable of producing hail and wind
damage. The wind damage threat would be greatest if a line of severe
storms can develop along the moist axis during the late afternoon
and early evening.

..Broyles/Wendt.. 11/30/2019


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