Lake winds are back Friday reducing temps here


The chill which has dominated so much of the past 5 weeks is back Friday thanks to the return of northeast winds off Lake Michigan’s chilly water.


Friday’s predicted 47-degree O’Hare high represents an 11-degree pullback from Thursday’s peak of 58—the year’s third warmest temperature to date.


That we’re into the year’s fourth month and a modest, early April 58-degree high ranks fourth among all 94 daytime highs on the books since Jan. 1 speaks volumes. It underscores just how cool the weather in Chicago has been.


Through Thursday, April’s opening four days averaged  7.5-degrees below normal and 16.9-degrees colder than a comparable period a year ago.  The chillier than normal readings of recent months have contributed to a Lake Michigan water temperatures 10-degrees colder than a year ago. Given the fact weather history here reveals easterly winds blow 43% of the time in April, the chillier than typical lake waters are not helpful in encouraging the seasonal warming for which so many Chicagoans are hungry.


91% of years have produced higher temps by now


Temperatures in 2013 have managed a reading no higher than the 63-degree high on Jan. 29. This is remarkably rare.


Midway Airport temperature data since 1928 indicates 77 of the past 85 years—91% of them—have recorded peak temperatures by April 5 which have come in higher than this year’s 63.


Despite the chill, comparably cool years have produced generous 90-degree tallies


This area’s warm weather enthusiasts may take heart in this stat. In 7 of 8 years (that’s 88% of them) which have displayed at Midway Airport the same lack of warmth we’ve seen this year, temperatures there have gone on to reach or exceed 90-degrees at rates equal to or greater than the typical tally of 23.


April’s generous sun has had only modest success in overcoming the chill


What’s quite fascinating about this month’s overall chill to date is that it’s occurred in the midst of generous supply of sunshine.


April, 2013 has logged 91% of its possible sun compared to a long-term average of just 52%. Often, cool springs are the result of limited sunshine and more extensive cloudiness and precipitation than usual—but not this year.


Instead, arctic-latitude blocking, brought on by higher than normal temperatures there, appears to be the driving-force behind the widespread Midwest chill. Blocking patterns there tend to displace cold air indigenous to those areas, relocating it farther south—in this case across the northern tier of  states.


Powerful south/southwest winds are to generate a Saturday temp surge


Friday’s chill yields to warming  southerly winds Saturday—a flow expected to send temperatures here surging to their highest levels of the year while producing wind gusts topping 30 mph.


Daytime highs Saturday are to reach the mid 60s despite the arrival during the afternoon of extensive cloudiness and possible showers. To date, 2013’s highest temperature has been 63-degrees on Jan. 29.


Next week’s rain to hit in waves; totals could approach 2 inches


A stormy weather regime is to develop across the nation’s mid-section next week. With the Gulf to “open” and send moist tropical air streaming northward, where it is to overrun cooler air reinforced by easterly winds off Lake Michigan within the southern flank of a sprawling Canadian high pressure to the north, the set-up becomes a meteorological recipe for precipitation—and possibly a good deal of it.


While rainfall is likely to arrive in distinct waves, with pauses between them, the potential exists to end up with close to 2 inches of rain over a wide swath of the Midwest—-including Chicago.