Severe Weather Returns to the Plains
As we move towards the middle of this weekend, severe weather chances will be on the increase across the central part of the country on Saturday. The SPC has highlighted an area from southern Wisconsin down through parts of Illinois, Iowa, Missouri, southeast Nebraska, and into central Kansas for a slight risk of severe weather.
A weak surface low pressure center will move slowly from eastern Colorado into west central Kansas. Throughout the day, a dryline extending down from the low will sharpen and move slightly east. Another boundary will setup northeast into southern Wisconsin.
Most likely, storm development will be focused on these two boundaries. Many question marks remain about storm coverage and intensity, but SPC has highlighted central Kansas in a “hatched” area for hail. A hatched area means significant severe weather is possible (in this case, hail > 2 inches). Storms will have to deal with shallow moisture and a stout elevated mixed layer (EML) capping off the atmosphere for much of the day. Hi-Res models have shown the cap in central to north central KS starting to erode by 22z-00z (5pm CDT – 7pm CDT). Moderate to strong instability (> 2500 J/kg of CAPE) as well as pockets of deep layer shear approaching 35-40 knots should aid in rapid supercell development should any storm break the cap.
CAPE values for 00z, 4/13/2014 - NAM
Supercell Composite Parameter 03zz, 4/13/2014 - NAM
Because of large temperature/dewpoint spreads as well as meager low level shear, the tornado threat seems minimal. However, it is important to note that SPC has highlighted the area in a 2% tornado risk. Elevated convection should form across much of the region over night with some isolated large hail and damaging wind risks.
Further northeast there is some uncertainty in regard to instability. The NAM paints a much more unstable picture than the GFS. Another limiting factor would be that the shear vector is generally parallel with the boundary, making a linear storm mode most likely at this time
Moving onto Sunday, The Storm Prediction Center has placed most of eastern Oklahoma in a moderate risk for severe weather with the main threats being large hail and damaging winds.
Tornadoes will be possible but will probably be most likely further south into north and central Texas should storms be able to break the cap. Most models have been suppressing convection in Texas so it is uncertain whether storms will be able form on the dryline that far south. As a strong cold front begins to crash down from the north through the day, we could see storms undercut by the boundary. If this scenario were to unfold quicker than forecast, the severe threat would most likely be greatly decreased. We will have more information about Sunday for you late tomorrow when we have a better handle on the potential. Mr. Twister’s own Zachary Hargrove will be out chasing both of these days to bring you live updates from the field. Please check back with us as details change!