Storms light up sky, pepper region with hail

Lightning flashed late Friday from low-topped thunderstorms across the Chicago area.
The storms bubbled into existence as a pool of unseasonably cold air at the heart of a
slow-moving storm system aloft swept directly overhead. It's a development which
encouraged 54-degree air at ground level to ascend into subfreezing air hovering less
than a mile above the surface and fostered hailstone formation. Quarter- to
half-inch-diameter hail was reported at Sugar Grove, Pecatonica, Elburn, Plano and
Flossmoor, as well as Munster and Crown Point in Indiana. The rainfall spawned by the
storm had pushed Midway Airport's two-day tally to 0.65 inches by late Friday. Heavier
rain totals occurred to the west where 1.01 inches fell at Pontiac, 0.92 inches at Morris
and 0.87 inches at Marseilles.
A classic high-wind scenario threatens to take shape Sunday as west-northwest surface
and jet stream winds align.
Subsidence as arctic air approaches could mix 40-50 m.p.h. gusts down to the surface --
inducing compressional warming which initially delays the onset of the coldest air but is
still likely to whisk the coldest air in six months into the area Sunday night and Monday.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune