A succession of downpour- and small- hail-producing thunderstorms erupted along an
inland-moving lake breeze Friday in southern Cook County, then swept into and across
northern Indiana. Winds converge at ground level along such lake- breeze fronts,
allowing air no recourse but to ascend in humid columns of air. The towering
thunderheads produced through this process -- referred to as cumulonimbus clouds
by meteorologists -- are often spectacular in appearance, taking on the form of
cottony masses within which lightning can be seen flashing. One of the storms
produced 0.60 inches of rain in just 10 minutes in Ft. Wayne, Ind.
Saturday will be rain-free -- cooled by north-to-northeast winds that import
noticeably drier air from Canada. Heat will begin to make inroads here Sunday, but will
likely be tempered by storm outflows.
BLAZING HEAT OVER 13 STATES REACHES
CHICAGO MONDAY INTO TUESDAY
High-temperature records fell in six states Friday, led by 104-degree highs in both
Denver and Miles City, Mont.
Excessive-heat advisories are posted for Saturday across 13 states from Montana to
Texas as an expanding western heat dome spreads into Chicago, bringing this
summer's hottest weather by Monday.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune
