Valid 211630Z – 221200Z
…THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
MINNESOTA AND WISCONSIN…AND OVER PORTIONS OF THE CENTRAL PLAINS…
…SUMMARY…
Large hail, damaging winds, and perhaps a couple of tornadoes are
possible this afternoon/evening from Kansas to Iowa, and across
parts of central Minnesota into northwest Wisconsin.
…MN/WI…
Morning surface analysis shows a weak low over northwest MN, with a
trailing cold front extending southward across the eastern Dakotas.
This front will move eastward today into central MN by
mid-afternoon, where a combination of daytime heating and forcing
associated with an upper trough tracking across the northern Plains
will lead to the development of widely scattered thunderstorms. 12z
model solutions are inconsistent on coverage of storms in this area,
but forecast soundings suggest a conditional risk of rotating storms
and the potential for hail and damaging wind in the strongest cells
that form. An isolated tornado or two is also possible, given the
presence of remnant outflow boundaries and ample low-level moisture.
Storms will move into central WI and weaken this evening.
…Central Plains…
The aforementioned surface cold front extends southward into central
NE/KS. Strong heating is expected this afternoon ahead of the front
from central/eastern KS into southeast NE, with MLCAPE values
approaching 3000 J/kg. Convective initiation is expected during the
late afternoon over central KS. Storms will build northeastward
across the SLGT risk area during the evening, with the potential for
large hail and damaging winds. Shear profiles will promote initial
supercell structures with a risk of very large hail. Persistent
clouds limit confidence in severe threat extending into
central/eastern IA.
..Hart/Bentley.. 09/21/2019
$$