Low-End Severe Weather Possible by Late Afternoon in Southern IA/Northern MO

Dr. Reed Timmer, Lead Meteorologist April 27, 2016

A strong, vertically stacked and negatively tilted upper-level storm system with 992 mb surface low is spinning over eastern Nebraska this afternoon, with a sharp warm front extending east across extreme southern IA and then southeast into northeast MO. Skies are beginning to clear in southwest IA/northwest MO with an arc of low-topped towering cumulus developing in extreme southeast NE east of the surface low. Depending on how far north the warm front retreats and the extent of clearing/surface heating near this boundary, a low end tornado threat could emerge especially in extreme southern Iowa.

SPC mesoanalysis short-term forecasts show 200+ effective helicities emerging near the retreating warm front in southern Iowa by late afternoon, but cloud cover could very easily remain entrenched in the region preventing any severe weather threat at all. Marginally severe hail will be possible with any convection in southern IA/northern MO given the cold temperatures aloft, and any rotating storms will have the potential to produce slightly larger hail stones.

Farther south, a severe thunderstorm watch remains in effect through 3 pm CDT for parts of southeast LA including New Orleans, but it appears the severe threat in this southern mode is lessening substantially with time as this line of storms becomes less organized. The strongest wind fields are well to the northwest closer to the negatively titled upper-level storm system over the central Plains and upper Midwest, and weakening with time in the south-central U.S.

A more substantial severe weather threat is still on the horizon across parts of the southern Plains, especially central/north Texas on Thursday and Friday. Large hail will again be the main threat with this system, but isolated tornado threat could emerge especially on Friday afternoon across N TX. Stay tuned for updates.