Valid 250100Z – 251200Z
…THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM THE
CENTRAL PLAINS TO THE UPPER GREAT LAKES…
Severe thunderstorms will persist from the central Plains to the
Upper Great Lakes this evening. Large hail, damaging gusts and a
few tornadoes remain possible.
Risk for a few tornadoes, along with locally damaging winds and
hail, is ongoing from the central Plains northeastward to the
western Upper Great Lakes at this time. Across this region, evening
RAOBs confirm a moderately unstable airmass, with winds veering and
increasing with height to west-southwesterly at 50 kt at mid levels
ahead of an advancing surface cold front.
These conditions are supporting widespread convection, including
embedded supercells. Several of these storms have exhibited strong
low-level rotation — aided by 0-1km shear near 30 kt —
particularly across portions of Iowa, southeast Minnesota, and
western Wisconsin. A couple of tornadoes have been confirmed in the
past 1-2 hours; for additional short-term information regarding the
ongoing tornado risk, please refer to SWOMCD #1214.
Otherwise, expect that increasing convective coverage and congealing
of individual updrafts over the next couple of hours, plus a
gradually stabilizing boundary layer — will permit the tornado risk
to begin diminishing prior to midnight. Risk for isolated hail and
locally damaging winds should linger, possibly beyond midnight and
into the overnight hours.