SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1159 PM CST Thu Dec 30 2021
Valid 311200Z - 011200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE ARKLATEX...MID MISSISSIPPI...OHIO AND TENNESSEE VALLEYS...
...SUMMARY...
Thunderstorms associated with severe weather will be possible today
and tonight from the southern Plains and Arklatex east-northeastward
into the mid Mississippi, Ohio and Tennessee Valleys. A few
tornadoes along with isolated large hail and wind damage are
expected.
...Southern Plains/Arklatex/Mid Mississippi Valley...
West-southwesterly mid-level flow will be in place today across much
of the central and eastern United States as a subtle lead shortwave
trough moves across the southern Plains. At the surface, a moist
airmass will be located from the southeastern third of Texas
east-northeastward into the lower to mid Mississippi Valley.
Thunderstorm development will be likely along the northern edge of
this moist airmass this afternoon from north Texas into southeast
Oklahoma with this activity moving into Arkansas late this
afternoon. Weak instability, strong deep-layer shear and adequate
forcing should be enough for an isolated severe threat. However,
uncertainty exists concerning the magnitude of the severe threat. A
lack of low-level convergence should keep the severe threat more
isolated this afternoon.
This evening into tonight, conditions for severe storms will rapidly
become more favorable as a shortwave trough moves quickly through
the southern High Plains. Low-level convergence will increase along
the northern edge of the moist airmass as a low-level jet
strengthens across the southern Plains and Arklatex. Scattered
thunderstorms are expected to develop in the Red River Valley during
the late evening along the northern edge of the low-level jet.
Thunderstorms will also likely develop eastward into the Ozarks. NAM
forecast soundings from 08Z to 10Z along this corridor have 0-6 km
shear near 80 kt with 0-3 km helicity approaching 400 m2/s2. This
should be favorable for supercells and a couple tornadoes.
Supercells should also be capable of producing wind damage and large
hail.
...Ohio and Tennessee Valleys...
West to west-southwesterly mid-level flow will be in place today
from the lower to mid Mississippi Valley eastward to the Atlantic
Seaboard. A moist airmass will be located across much of the
Tennessee Valley this afternoon where surface dewpoints should be in
the mid 60s F. As weak instability increases during the afternoon,
isolated thunderstorms are expected to develop from Tennessee into
southern Kentucky. Strong deep-layer shear should support an
isolated severe threat with the initial activity. This convection
could struggle at first due to a lack of low-level convergence.
However, the severe threat should gradually ramp up during the
evening as a low-level jet strengthens and a fast-moving shortwave
trough approaches from the west. Thunderstorms are expected to
gradually increase in coverage during the mid to late evening from
western Kentucky into western Tennessee.
Forecast soundings in western Tennessee from 06Z to 09Z show MLCAPE
in the 500 to 750 J/kg range with 0-6 km shear near 70 kt. This
combined with increasing low-level convergence and a strengthening
low-level jet will likely support severe storm development this
threat continuing into the overnight period. Storms that develop
along the northern edge of the low-level jet will move
east-northeastward across the Ohio and Tennessee Valley with a
threat for a couple tornadoes, wind damage and isolated large hail.
..Broyles/Lyons.. 12/31/2021
Read more LIVE: spc.noaa.gov
http://dlvr.it/SGJC9l
