Chicagoans brace for early March level temperatures Tuesday, with readings more than
15 degrees below normal, as the area moves into an 11th consecutive day of subnormal
temperatures. This month's 41.0-degree average temperature is 3.6-degrees below the
long-term 138-year average--cool enough to rank among the chilliest 20 percent of
April 1-14 periods on the books. It's the first April here in 25 years that has failed to
host a single 60-degree daytime high.
The Chicago area remains mired in the same damp, raw northeasterly flow responsible
Monday for the chilliest Cubs home opener since 2004. The storm system behind the
gray skies, expected to linger into Wednesday morning, has become ensnared in what
meteorologists refer to as an atmospheric blocking pattern. These patterns involve jet
stream configurations that impede the forward movement of weather systems under
their control. In this case, a pool of warm air aloft over southern Canada has
encouraged jet stream winds to split into two distinct channels. As these streams
re-converge over the Northeast U.S., the confluent winds produce a pressure build-up
aloft that forces air to sink to the surface on a massive scale. A high pressure system
results which slows weather system movement to the west.
City's wettest meteorological spring in 26 years
The 8.61 inches precipitation tally since March 1 at Midway Airport is not only twice
the long-term 81-year average, it makes this the wettest spring to date since 1983
and second wettest of the past eight+ decades at the South Side site.
-Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune
