Temperatures surged Thursday, making it feel like spring-yet snow may
fall this weekend in parts of the Chicago area. Most prone to get snow
appear to be areas away from Lake Michigan, which could see chilly,
wind-driven rain switch to snow or sleet late Saturday afternoon or
night.
So many factors are at work this late in the season to prevent snow
from occurring-longer days, more intense sunlight and warmer ground and
lake temperatures among them. But 65 percent of the past 124 years have
produced measurable snows (0.1 inch or more) beyond March 27. The
intensity of the most intense snows has been eye-catching, like the 12.6
inches that accumulated March 30-31, 1926; the 10.7 inches on April 1-2,
1970; and the 9.8 inches on April 2-3, 1975.
This weekend's snows aren't likely to be as intense. But sub-32-degree
dew-point air, which cools through evaporation once rain begins falling
into it, and the "dynamic cooling" brought on by the strong upward rush
of air as a strong batch of jet stream winds sweeps in, argue for a
shift to at least some wet snow and sleet later Saturday and Saturday
night-especially away from Lake Michigan. Rising air cools because the
surrounding air pressure drops, encouraging it to expand and cool. The
storm's backside north winds are also likely to latch on to chilly air
south from the Upper Midwest and Canada.
Colorado was declared a disaster area Thursday as blizzard
conditions-including 20 inches of snow and gusts that reached 100 m.p.h.
in some canyons-brought travel to a standstill.
Thursday's "warmth" to prove fleeting
It was like spring Thursday! Highs reached 61 degrees at Chicago's
lakefront as well as in Libertyville, Wheaton and New Lenox.
