2013 has featured an unusually low tornado count, but the number of touchdowns will be on the rise this weekend. The long range outlook has highlighted a large swath of the plains for being under the risk of severe weather Saturday (purple) and Sunday (green). The SPC is fairly confident considering that they are highlighting areas five and six days in advance.
SPC’s five day outlook includes a risk for nearly all of eastern South Dakota, eastern Nebraska, and northeast Kansas. Storm activity may be somewhat limited Saturday afternoon & evening due to a capping inversion (warmer air aloft). However, any supercells that do fire along a dry line boundary will have to be monitored closely for tornado potential. Based on the 18Z run of the GFS model, the threat area may eventually have to be extended southward, closer to Garden City. Low level shear will increase across central Kansas near sunset.
The threat of severe storms will slowly prograde eastward by Sunday. During the afternoon hours, a sub-1000mb surface low will be located over far northwest Iowa. The best low level shear values for tornadogenesis will exist east and southeast of the low, and Sunday’s highlighted area by the SPC still appears to be on track.
The severe weather threat may continue into early next week across the Mississippi & Ohio Valleys, however significant uncertainty exists beyond day six.