Short Range Technical - Coffman
Main focus of the short range will be based on the strong storm system moving in for tomorrow afternoon and evening through the midwest and the Ohio/Tennessee river valleys. Storm will be developing over Arkansas today and will quickly deepen and strengthen as an area of strong sinking motion moves into an area of rising motion over the plain states. The pressure gradient, as well as the temperature gradient, will strengthen quickly. As the storm increases and moves to the northeast, a warm front will advect warm air into the upper midwest Thursday morning. On the backside of the low, incredibly strong CAA (to the tune of -100+ K/day) will be moving towards the state of Indiana Thursday night. This will lead to an incredible drop off in temperatures when the front passes, 850 temps will drop almost 20 degrees C/K over a 6 hour period (according to the GFS 12Z).
Taking our attention to vorticity advection, the strengthening low will cause a very strong area of PVA ahead of the low, and very strong NVA on the backside. This will be being forced by some very strong winds in the mid levels, as some 120 knot winds can be observed at 500mb as the vort max passes overhead. A strong LLJ is bringing 60-70 knt winds along with this storm as well.
Severe weather threat could be evident over the southern half of Indiana, Kentucky, and points further south. Some CAPE values of up to 1000 J/kg could be noted there, which is incredibly strong for this time of year. It won't take too much instability to bring those winds to the ground, so some severe gusts are possible. Best chance of severe weather will likely be in areas where we see negative lifted index, which is noted from far southern Indiana and points south. Severe threat north of I-70 has decreased substantially because of the existing snow pack, which will increase the inhibition over that area and make buoyancy more difficult. Also, the dynamics are much stronger to the south (as noted).
A couple more things to mention. GFS has the low pressure deepening to 970mb, which will bring blizzard like conditions to Wisconsin and Iowa. This tight pressure/temperature gradient will bring some very high winds, and NWS is considering a High Wind Warning for parts of Indiana tomorrow night. Wind gusts could reach in excess of 35 knts tomorrow night. As the cold air advection works its way in, a VERY brief period of snow could be noted on the backside of this system with any remaining precipitation.