Although the coverage of storms was limited on this Tuesday afternoon and evening, the first severe thunderstorm event of 2012 featured the first-ever documented February tornado within this six-county portion of North Central Kansas. This EF0 tornado touched down five miles southeast of Randall in Jewell County at 528 PM and tracked east for roughly two miles, tearing a metal roof from a farm outbuilding along the way. Other than this tornado, the only other severe weather report was a 63 MPH wind gust at the Phillipsburg airport, from a combination of strong winds behind a passing cold front and downdrafts from light rain showers falling through dry air.
Breaking down the event, a few non-severe elevated thunderstorms lifted from north to south across the area between 10 AM and 12 PM. In the wake of this early activity, modest clearing and resultant destabilization worked into western portions of the area during the early afternoon, in association with an advancing mid level dry slot. As a result, a few non-severe storms first developed into portions of Rooks and Phillips Counties between 215 PM and 3 PM. Around 330 PM, the thunderstorm cluster that would eventually produce the tornado near Randall initiated just south of the area near Interstate 70. As this storm cluster drifted northeast into Osborne, Mitchell and southeast Jewell Counties it became increasingly organized, and rapidly assumed supercell characteristics and strong low-level rotation near and northeast of Beloit, before exiting the local area into Republic and northwest Cloud counties. A few more linear storms affected Jewell and Mitchell Counties after 7 PM, but all thunderstorms exited the six-county area by 8 PM.
On the synoptic scale, this was a classic early-season severe weather setup for the area, featuring a strong, negatively tilted mid and upper level trough ejecting out of the Central Rockies into the Central Plains. At the surface, a well-defined surface low pressure system deepened to around 994 millibars as it tracked from east-central Colorado at mid-day, to central Nebraska by late afternoon. To the south of this low, a well-defined cold front and dryline surged east into central Kansas, sparking supercell development. Late afternoon mesoscale parameters revealed a highly-sheared but only modestly unstable environment with surface dewpoints only in the low-mid 50s. Although surface-based CAPE only averaged around 1000 J/kg, both deep layer vertical wind shear and low-level 0-1 kilometer shear were quite impressive, topping out around 70 knots and 30-40 knots, respectively. At the time of the tornado in Jewell County, effective storm relative helicity values were at least 500 m2/s2.