Supercells possible in OKlahoma this afternoon!
The cap is almost eroded over much of western Oklahoma as of 20z with temperatures rising through the 80s, and a line of concentrated cumulus-towering cumulus has developed on visible satellite imagery, leading to the issuance of a mesoscale discussion over this area for a severe thunderstorm watch (and maybe a tornado watch if low-level shear looks to improve). CAPE values of 2500+J/kg with mid 60s dewpoints holding on against diurnal mixing with the help of some evapotranspiration. Two factors that may limit or eliminate initiation today in western OK is minimal surface convergence in western OK where the TCU are developing (seem to be along moist convective rolls coinciding with moisture gradient), including along the dryline near the OK/TX border where wind speeds are weak; and slight subsidence with very slight ridging aloft. Low-level
shear profiles still look a little weak in OK according to Frederick and TLX VAD at around 20z, but there is decent turning in the low-levels evident to the east of the towering cu central Oklahoma. The RUC is also hinting at a strengthening low-level jet as sunset approaches, and I've chased several events where the LLJ strengthens faster than anticipated with the trough well to the west. As I've typed this blog post, the cumulus/tcu are becoming more concentrated, but are still not breaking what remains of the cap as they are not showing up on nearby radar echo tops. Time will tell if the weak convergence along the moisture boundary can be enough to get these storms to fire, but if they take off TVN will be surging west from Norman and streaming live to
http://www.tornadovideos.net/live. If storms can develop, and I am leaning in that direction, then there is a small chance of a tornado or two as the LLJ intensifies this evening. As the trough begins to eject, wind shear will not be a problem tomorrow (Saturday) and Sunday -- looking like potential tornado outbreaks from central KS/Iowa to eastern Iowa/western IL/southern MN/WI, respectively, with Sunday looking particularly widespread. The SPC has already issued a moderate risk for the Day 3 outlook for the aforementioned area. Stay tuned for updates as new model runs become available.
http://www.tornadovideos.net/component/content/article/1-latest-news/1341-supercells-possible-in-oklahoma-this-afternoon
