The Chicago area’s next warm spell is likely to be more humid and to last longer than any of its brief 2007 predecessors if current forecast scenarios prove true. At least three 80s are in the current forecast beginning Sunday?and the warm spell could end up lasting even longer thanks to “atmospheric blocking” predicted to take shape across North America. Atmospheric blocking takes place when upper steering winds become “wavy” or diverge into a series of different streams. The predicted upper wind configuration above the continent this weekend is to take on the shape of the Greek alphabet letter “omega”?an orientation known to bring the eastward progression of large air masses–including the dome of warm air predicted to cover much of eastern and central North America — to a veritable halt. That could lock Chicago in warm weather well into next week. Three days of temperature-restricting easterly winds off Lake Michigan (through Friday) are to occur first.
Sources: NOAA-NCEP, NWS Chicago, Frank Wachowski
WGN-TV/Thomas Valle, Anna Gasper and Dave Peterson
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Tom Skilling is chief meteorologist at WGN-TV. His forecasts can be seen Monday through Friday on WGN-TV News at noon and 9 p.m.
WGN-TV meteorologists Steve Kahn, Richard Koeneman and Paul Dailey plus weather producer Bill Snyder contribute to this page.
