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Here are some graphics from the SPC Mesoanalysis page, which is based on a RUC computer model analysis of the atmosphere at the indicated times. SBCAPE is surface based CAPE, a measure of instability in the atmosphere. Eff. Shear is effective wind shear which measures the amount of deep layer wind shear that a thunderstorm may experience. 30 to 40 knots or more is typically favorable for supercell thunderstorms - powerful rotating storms. Eff. SRH stands for effective storm relative helicity in which higher values tend to favor thunderstorms with rotating updrafts. STP stands for Significant Tornado Parameter which combines a number of different variables in the atmosphere to gauge the potential for strong tornadoes (EF2 or stronger); values of 1 or more are considered "favorable".
Below is a radar image from 5:31 PM CDT from Bayfield County. The large spike of low reflectivities extending southeast from the storm is what is referred to as a "three body scatter spike". These spikes are commonly indicators of a thunderstorm producing severe hail. We received reports of golfball size hail from these areas in Bayfield County. To the right of the radar image is a graphic explaining briefly how the "three body scatter spike" works.
|5:31 PM CDT Radar Image - Bayfield County
||Graphic Explaining Three-Body Scatter Spike