RECORD BREAKING THURSDAY WARMTH TO GIVE WAY TO THE COLDEST WEATHER YET THIS SEASON–TEMPS BY SUNSET FRIDAY WILL BE 30-deg COLDER IN THE CHICAGO AREA—EACH OF THE COMING 15 DAYS TO COME IN THE “BELOW NORMAL”AVERAGE TEMPS

The proportion of the Lower 48 covered with snow out to our west surged to a season high of 20% early today. That’s important because a reflective cover of snow is the track over which cold air rides into the area. And even though snow has yet to cover the Chicago area, or for that matter, anywhere close, it enables chilly air off the growing Canadian snowpack to reach deeper into the U.S.A markedly colder weather pattern is about to descend–not just on Chicago–but on a huge swath of the continental U.S. Changing upper winds will see a persistent northwest flow at the steering levels of the atmosphere into Chicago through much of the coming two weeks. The effect will be dramatic on Midwest temps.

Here in Chicago–the mid 70s we are enjoying Thursday–temps which exceeded previous highs—will have fallen back to the upper 30s to low 40s by the time the sun sets Friday.

33% of the country saw 70s today. By Sunday the area with 70s will have shrunk to just over 1% of the contiguous U.S. The expansion of sub-freezing temps will be equally dramatic. While 51% of the Lower 48 will have a freezing or lower low temp by Friday morning, the area of sub-freezing low temps will have grown to 73% of the U.S. by Sunday morning.

And snow flurries may fly here Saturday–but there are indications they won’t be the last over the next two weeks. All of the major global models are predicting additional snowflakes in the coming 2 weeks.And in terms of 32-deg or colder temps across the Lower 48