Chicago to get its first true taste of spring

Spring - "astronomical spring" - arrives March 20, the date (known in
astronomical circles as the vernal equinox) on which the sun's rays
shine directly down on the equator as the sun makes its annual trek into
the Northern Hemisphere. More figuratively, our seven-day forecasts
suggest that spring arrives in Chicago this week, though its arrival
will be in fits and starts. Afternoon temperatures in the low 60s Monday
will jump 10 degrees into the low 70s on Tuesday, but then the spring
feel will give way to a midweek reality check with Canadian air and rain
Wednesday. That's followed on Thursday by a genuine - albeit brief - cold
punch that delivers temperatures more typical of January than mid-March.
BIG STORM SYSTEM FOR WEEKEND
It's mainly a Northwest U.S. affair as it blasts from the Pacific Ocean,
then swings northeast into Canada. Computer models indicate its wind
field will be so expansive that it will generate strong southerly flow
across the Midwest, nearly 2,500 miles away. Chicago's temperatures will
surge toward the weekend, along with a heightened thunderstorm risk as
increasingly unstable air arrives from the south.
--By Richard Koeneman, WGN Weather Center Meteorologist