Severe weather and isolated tornadoes possible today in IA!
A potent upper-level shortwave will surge across the Central Plains today, creating a very strongly sheared environment to its immediate east over central and eastern Iowa this afternoon and evening. Hodographs actually look favorable for even strong tornadoes across Central Iowa after 21z as a 40-50+ knot low-level jet stream intensifies through the afternoon, but low-level moisture quality could be a limiting factor given the passage of multple intense cold fronts that have scoured out the moisture over the last few weeks. If 65-70F dewpoints were in place over this region, I would not be surprised if today's event was given a moderate or high risk. However, realizing these moisture concerns, the SPC has hoisted a slight risk with 5% tornado probabilities over central Iowa into southern Minnesota/southwest Wisconsin for today and overnight. It is incredible how the jet stream pattern has remained favorable for severe weather events across the central U.S. throughout the spring and summer storm season, with substantial troughs traversing the Plains on a weekly basis, but this system looks to have very marginal moisture to work with. The surface map below tells the story, with a small area of 60F+ dewpoints advecting northward from Kansas into Nebraska ahead of the developing surface low, but is quickly getting "pinched off" by intense mixing over Kansas. The progressive nature of this trough will also not allow sufficient time for deep moisture to advect northward, so it looks like upper 50s to low 60s will be the reality this afternoon across the slight risk area. Forecast soundings across the warm sector also show the relatively dry low-level conditions, as seen below from near Cedar Rapids, IA at around 00z. Still though, a tornado or two will be possible as storms quickly develop this afternoon ahead of the upper-level speed max, and TVN live streamers will be in the field documenting this event at
TornadoVideos.net/live. Stay tuned for updates!
http://www.tornadovideos.net/component/content/article/1-latest-news/1274-severe-weather-and-isolated-tornadoes-possible-today-in-ia
