- Day Three
acus03 kwns 180707
Storm Prediction Center ac 180706
Day 3 convective outlook
National Weather Service Storm Prediction Center Norman OK
0206 am CDT Wed Jul 18 2018
Valid 201200z - 211200z
..there is a slight risk of severe thunderstorms across parts of
the middle Mississippi...Ohio and Tennessee valleys...
A severe threat will be possible on Friday across parts of the mid
Mississippi, Ohio and Tennessee valleys...
..mid Mississippi/Ohio and Tennessee valleys...
An upper-level trough will become more amplified and move
east-southeastward into the western Great Lakes region on Friday as
a 50 to 65 kt mid-level jet moves through the southwestern part of
the system. At the surface, a low is forecast to move into the
western Great Lakes as a cold front advances eastward into the lower
Ohio Valley. Elevated thunderstorms could be ongoing in the morning
well ahead of the front with this convection moving eastward away
from the greatest instability during the day. Just ahead of the
front, a moist airmass is forecast to be in place across much of the
mid Mississippi, Ohio and Tennessee valleys where surface dewpoints
should be in the upper 60s and lower 70s f. In response to surface
heating, moderate to strong instability is forecast to develop from
western Tennessee northward through western Kentucky and southern
Indiana. Thunderstorm development will be possible along the
northern side of the strongest instability from southeast Illinois
southeastward into western and central Kentucky late Friday
GFS forecast soundings at Paducah, Kentucky and Evansville, in for
00z/Saturday show MLCAPE value around 3500 j/kg with 0-6 km shear in
the 50 to 60 kt range. This combined with steep mid-level lapse
rates should be favorable for supercells with large hail. A wind
damage-threat and isolated tornado threat will also be possible. The
wind-damage threat could become more prominent in the early evening
as a cluster or line of storms moves southeastward across the Ohio
and Tennessee valleys.
Over the last few days, the models have been fairly consistent from
run to run concerning friday's scenario. Also, the models are in
decent agreement on the latest run suggesting that confidence is
high enough to add a slight risk across parts of the lower Ohio
Valley for Friday.