Valid 011300Z – 021200Z
…THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PARTS OF THE
CENTRAL PLAINS EAST-NORTHEASTWARD INTO THE MID TO UPPER MISSISSIPPI
Isolated strong to severe storms are expected from late afternoon
into the mid evening from parts of the Great Plains into the Mid
Missouri Valley and Great Lakes.
…Southern and Central Plains/Mid Missouri Valley/Mid to Upper
A high-pressure system will be in place today across the Southeast
U.S. as an upper-level trough moves across the Intermountain West.
Southwest mid-level flow will be in place the central states. At the
surface, a cold front will advance southeastward and should be
positioned from the Texas Panhandle northeastward into central
Kansas and central Iowa by late afternoon. Ahead of the front,
surface dewpoints from the mid 60s to the lower 70s F should result
in moderate instability mainly from eastern Kansas to northern
Illinois. Thunderstorms are forecast to develop late this afternoon
along the much of the front from the southern Plains to the mid to
upper Mississippi Valley. This convection should persist into the
early to mid evening.
RAP forecast soundings along the instability axis at 00Z/Wednesday
from Salina, Kansas to Des Moines, Iowa show MLCAPE reaching 1500 to
2000 J/kg range with steep low-level lapse rates. Wind profiles show
directional shear from the surface to 700 mb with 0-6 km shear in
the 40 to 50 kt range. This environment could be favorable for
supercells where cells remain discrete and instability becomes the
strongest. However, cell motions nearly parallel to the front should
result in linear development in most areas with supercell
development less likely as the event progresses. Poor mid-level
lapse rates should minimize hail production but the more organized
line segments could produce damaging wind gusts.
A high pressure system will remain over the Ohio and Tennessee
Valleys today with westerly mid-level flow in the Great Lakes
region. At the surface, a cold front will advance southward into the
southern Great Lakes, being positioned from southern Wisconsin
eastward across central Lower Michigan. Surface dewpoints in the
upper 60s F to the south of the front should result in gradual
destabilization throughout the day. Thunderstorms appear likely to
develop along much of the front during the afternoon. Although
instability is forecast to remain weak in most areas to the south of
the front, moderate deep-layer shear and steep low-level lapse rates
may be enough for a marginal wind-damage threat late this afternoon.
The threat would be greatest with multicell line segments that move
east-to-west in areas the have the strongest instability.