SPC AC 150056
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0756 PM CDT Tue Sep 14 2021
Valid 150100Z - 151200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL PLAINS AND SOUTHERN GREAT LAKES...
...SUMMARY...
Scattered storms with damaging winds are expected this evening into
tonight in parts of the southern Great Lakes. Severe storms with
large hail and damaging winds will also be possible this evening
into early tonight from eastern Colorado into southwestern Kansas. A
tornado could occur through tonight across southern Louisiana,
southern Mississippi and southern Alabama with the remnants of
Nicholas.
...Central Plains...
The latest radar imagery from Dodge City shows two clusters of
strong to severe thunderstorms. The first cluster is in
south-central Kansas along and to the north of a east-to-west
oriented cold front. Moderate instability is analyzed by the RAP
along this corridor. The 00Z sounding from Dodge City has MLCAPE
near 1500 J/kg with 0-6 km shear at 50 knots. Some directional shear
is present in the low to mid levels. This will likely support
continued supercell development this evening. Hail and wind damage
will be the primary threats...see MCD 1751. The threat should become
more isolated late this evening into the overnight period as the
storms move into southeast Kansas where deep-layer shear is weaker.
The second cluster of strong to severe thunderstorms is located from
west of Lamar, Colorado southward to near Raton, New Mexico. This
convective complex is in an area with easterly upslope flow. A
subtle shortwave trough is evident on water vapor imagery in the
eastern Colorado which will continue to support convective
development into the early overnight period. The latest RAP in
southeast Colorado has MLCAPE between 500 and 1000 J/kg, 0-6 km
shear near 45 kt and 700-500 mb lapse rates around 8.0 C/km. This
will be favorable for supercells with large hail and isolated wind
damage. The severe threat should persist into late evening as the
complex moves eastward into southwest Kansas.
...Southern Great Lakes...
The latest radar imagery from Indianapolis and Detroit show a
multi-segmented line of strong to severe thunderstorms from southern
Illinois northeastward into southeastern Lower Michigan. The line is
just ahead of a cold front where surface dewpoints ahead generally
from 65 to 70 F. MLCAPE is estimated by the RAP from near 2500 J/kg
in southern Illinois to around 1500 J/kg from northeast Indiana into
southeast Lower Michigan. Regional WSR-88D VWPs along and ahead of
the front have unidirectional west-southwesterly winds above the
boundary layer with 0-6 km shear around 40 kt. This will support a
wind-damage threat with the better organized multicell line
segments...see MCD 1750. The wind-damage threat could persist into
late evening with line segments that are near the stronger pockets
of instability.
...Central Gulf Coast...
The remnants of Nicholas will continue to move east-northeastward
across the lower Mississippi Valley and central Gulf Coast region
late this evening. The latest RAP is analyzing a low-level jet
across southern Louisiana with 850 mb winds in the 20 to 30 kt. This
is sampled by the New Orleans WSR-88D VWP which shows gradually
veering winds with height and 20 knots of flow in the low to
mid-levels. This should be enough for a marginal tornado threat this
evening, mainly with semi-discrete rotating cells.
..Broyles.. 09/15/2021
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