Mild through Friday, then colder — then snow?

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CHICAGO — November, 2016 has produced 82% of possible sunshine, at a time of the year when 42% is normal.

Temperatures have responded by posting a surplus of nearly 9 degrees.

There has yet to be a day this month that has averaged below normal in temperature.

Our mild weather has resulted from the jet stream being positioned well to the north, keeping colder, polar air confined to central and northern Canada.

Late Monday, satellite imagery showed a pocket of elevated jet stream winds over the north Pacific. This feature is forecast to reach the West coast by Thursday, causing low pressure over the central Plains to evolve into the first major storm system of the season across the central U.S. High winds are to sweep near record warmth into the area Thursday, followed by sharply falling temperatures Friday night.

The season’s first snowflakes may occur Saturday.

For the latest weather updates, go to WGN Weather Center