Skip Talbot
EF5
Tomorrow looks like a pretty decent chase opportunity although more modest in overall tornado potential. NAM has been showing a sub 1000 mb surface low moving northeast from the high plains into NE/SD with a warm front draped e to southeast from central SD into southwest MN. A little trough and modest impulse is also forecast to bring 30-40 knots of southwesterly midlevel flow to SD.
Some of the wind profiles look great across eastern South Dakota. We've got nicely backed surface winds on the warm front, ample veering with height, and adequate speed shear values of 30-50 knots. Effective helicity goes over 200 on the warm front. Hodographs showing nicely curving loops. A discrete supercell coming off the low and heading to the warm front has a shot at putting down a tube.
Several concerns of course. My first would be the environment along and behavior of the warm front. It looks like it's steadily lifting north during the day with ongoing junkvection north of the front. South of the front, the 700 mb temps look pretty toasty until early evening. I hope the warm sector doesn't stay capped with veered winds, while the warm front just keeps pushing north steadily behind the morning MCS with no destabilization. We could see a quiet warm sector with only elevated hailers north of the front. Forcing in the warm sector looks weak with modest flow aloft and even some slight height rises.
My other concern is storm mode. Weak upper level winds, slow moving cells, and very high precipitable water (over 2 inches) favor high precipitation storms.
Still, if the cap holds initiation off until late afternoon, there could be a window for discrete supercells to produce along the warm front in favorable shear before a transition to HP. The 700 mb temps cool off along the surface low after 21z. Lid strength index values open along the warm front starting at about that time, staying wide open through 0z before filling in after dark.
Initial target is going to be Huron, South Dakota at 21z (4pm) for initiation of supercells, tracking toward a Watertown, SD area by 0z (7pm) hopefully producing along the warm front before a transition to HP. Otherwise, would expect this day to feature mainly elevated hailers north of the warm front, or a line of HP supercells and an MCS extending from Pierre down into northern NE tracking into MN by evening as an elevated MCS. Nasty green cores and gustnadoes would probably be the chase catch of the day then rather than a photogenic tube.
Some of the wind profiles look great across eastern South Dakota. We've got nicely backed surface winds on the warm front, ample veering with height, and adequate speed shear values of 30-50 knots. Effective helicity goes over 200 on the warm front. Hodographs showing nicely curving loops. A discrete supercell coming off the low and heading to the warm front has a shot at putting down a tube.
Several concerns of course. My first would be the environment along and behavior of the warm front. It looks like it's steadily lifting north during the day with ongoing junkvection north of the front. South of the front, the 700 mb temps look pretty toasty until early evening. I hope the warm sector doesn't stay capped with veered winds, while the warm front just keeps pushing north steadily behind the morning MCS with no destabilization. We could see a quiet warm sector with only elevated hailers north of the front. Forcing in the warm sector looks weak with modest flow aloft and even some slight height rises.
My other concern is storm mode. Weak upper level winds, slow moving cells, and very high precipitable water (over 2 inches) favor high precipitation storms.
Still, if the cap holds initiation off until late afternoon, there could be a window for discrete supercells to produce along the warm front in favorable shear before a transition to HP. The 700 mb temps cool off along the surface low after 21z. Lid strength index values open along the warm front starting at about that time, staying wide open through 0z before filling in after dark.
Initial target is going to be Huron, South Dakota at 21z (4pm) for initiation of supercells, tracking toward a Watertown, SD area by 0z (7pm) hopefully producing along the warm front before a transition to HP. Otherwise, would expect this day to feature mainly elevated hailers north of the warm front, or a line of HP supercells and an MCS extending from Pierre down into northern NE tracking into MN by evening as an elevated MCS. Nasty green cores and gustnadoes would probably be the chase catch of the day then rather than a photogenic tube.
