Monday temp plunge the equivalent of an early autumn to early winter temp change in just 24 hours; the coldest weather since March now grips the metro area


The area’s first truly wintry blast of cold air this season swept into the area on powerful west winds which gusted to 40 mph and trapped wind chills in the teens and 20s Monday.


Thermometer readings across Chicago’s western suburbs failed to rise out of the low and mid 30s–December level readings! McHenry county’s Harvard and DeKalb county’s Sycamore recorded Monday highs of just 32-degrees, while Lake Geneva, Schaumburg and St. Charles were gripped by temperatures which rose no higher than 34.


In the city proper, the cold blast crushed Saturday and Sunday’s unseasonable 66 and 70-degree highs, replacing them with an official O’Hare high of 40-degrees—the site’s coldest daytime reading in the over 8 months since the 37-degree max temp March 5. And Tuesday’s 43-degree predicted high is more typical of late rather than of mid-November. It falls 7-degrees shy of the “normal” Nov 13 high of 50-degrees.


The city’s first official flurries of the season arrive Monday—a bit later than average


Several spells of snow flurries accompanied the cold air into the area Monday. While some sections of the Chicago area were treated to flurries early in the pre-dawn hours, it was the evening and early nighttime hours on Monday which put on the best show with flurries which reached into the city for the first time since March 30 this past spring. The opening flakes of the 2012 season were recorded at Midway Airport at 5:20 p.m.—9 days beyond the Nov. 3 average since 1997.


The snowpack across the Lower 48 expands 13-fold over the past 10 days; nearly a third of the contiguous U.S.—including sections of 21 states—covered by snow as the new week opens


The cold air which grips the area Tuesday morning has produced widespread snowfall over the past week across the West and into the northern Plains. The area covered by snow across the Lower 48 snowpack has expanded to an area more than 13 times as large as just 10 days ago on Nov 2.—31.5-percent of the Lower 48 versus just 2.4% in early November. Snow now covers the ground across sections of 21 of the Lower 48 states.



Flow of arctic air being stymied by westerly upper air flow


The current cold air mass won’t be followed by another cold blast right away.  Greenland blocking has broken down for the time being and upper steering winds have become “zonal” or “westerly”, guiding mild oceanic air into the country and holding new arctic air at bay.



Over time, temperatures will head higher. But, the process will be a slow one into this weekend. The highest temperatures arrive next week, but their progress into the area any earlier than that will be slowed by easterly winds off Lake Michigan expected to take up residence here this weekend.



A sprawling high pressure, which is to be draped across eastern Canada and the Great Lakes, in combination with lowering pressures over the western Atlantic this weekend, will deliver days of easterly winds to Chicago, slowing warming here.



Looking further into the future, indications appear to favor a mild, windy Thanksgiving with temps nearing or surpassing 60-degrees.



New Mid-Atlantic nor-easter threat late this weekend into next week?



As unbelievable as it sounds, a new nor-easter could be brewing for the Mid-Atlantic and possibly New England. The new storm could subject coastal areas of the region to  a new round of howling easterly winds later this weekend and into next week.