WGN-TV Chief Meteorologist Tom Skilling and the WGN Weather Center staff provide daily coverage of weather in the Chicago area.

It can hit 70 this time of year--it did a year ago

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Shorter days and weaker, low angle sunlight make it harder to warm this time of year--but that doesn't keep mild temperatures from happening. The atmosphere just has to work harder to produce such "warmth"--by, for instance, generating stronger winds which blow from warmer regions into the Midwest before the incoming air can cool---or by minimizing cloud formation capable of blocking sunlight. It also doesn't hurt to sit beneath the nose of a pocket of powerful jet stream winds, where air sinks, compresses and warms on a broad scale---a setup predicted to fall into place this weekend. That warmth can occur this time of year was evident a year ago. The area was in the midst of a three day 70-degree spree.  Last year's 71 degree high on this date was 18-degrees warmer than the 53 predicted Thursday.

Barring more extensive cloud development Saturday than is currently predicted, readings then could reach 70-degrees for the first time since Sept. 27. Late season 70-degree temperatures aren't common, but they have occurred beyond Nov. 5 an average of one year in three since records began at Midway Airport 80 years ago.

The coming warm-up---likely to produce the first set of back-to- back weekend 60s here since late September---may well be part of a three day spell of 60-degree-plus highs extending from Saturday through Monday. Three consecutive 60s have occurred here this late in the season in 44 percent of years on record.

Frigid arctic air remains trapped in northern North America where temperatures in recent days have dropped as low as 20-degrees below zero. In stark contrast, the tropics remain active. Tropical Storm Ida---with 65 mph winds and gusts of hurricane strength--formed Wednesday off the coast of Nicaragua. The system will lose strength as it punches into Central America on a northward trek.  But, it's possible we've not heard the last of the system. It could emerge into the southern Gulf of Mexico off the Yucatan Peninsula in the next week where reorganization would occur.


Humidity surge this weekend will add to mild "feel"---over-development of clouds would thwart warming
 
Dew points, which reflect atmospheric moisture and have resided in the 30s in recent days, are to take off this weekend as Gulf moisture mixes with mild but comparatively dry Pacific air moving in from the west. They are to reach the 50s which will lead to a noticeably more "humid" feel to the air Saturday and Sunday just as temperatures surge. This should lead a mild feel to the air not experienced here since September.