Arctic Blast a December Reality Check for the Midwest and East This Week Thanks to a Major Weather Pattern Change

A weather pattern change this week will bring sharply colder weather to the central and eastern U.S.

This cold air is increasingly likely to linger at least into the second week of December.

In the meantime, relatively mild temperatures will dominate the southern and eastern states through Tuesday.

A sharp pattern change this week will return colder weather to much of the central and eastern United States that may last into at least the second week of December.

Before this cold blast arrives, many areas of the East and South will have another day to enjoy the relatively mild conditions that have encompassed the central and eastern states since last week.

Forecast Highs This Week

  The jet stream pattern will then amplify in a north-to-south fashion with a southward plunge setting up east of the Rockies. This type of weather pattern typically opens the gate for colder air to infiltrate the eastern half of the nation.

A southward dip in the jet stream sandwiched between two northward jet stream bulges will allow colder air to dive south across the central and eastern states this week.

High temperatures will return to near average on Tuesday in the Plains and parts of the Midwest. By Thursday, all areas east of the Rockies will experience near- or below-average temperatures.
Areas from the Midwest into the Northeast will see highs in the teens, 20s and 30s by late week instead of the 40s and 50s that have started the week. Single-digit highs are even possible in the upper Midwest near the Canadian border. In much of the South, highs in the 40s and 50s will replace temperatures in the 60s and 70s.
This upcoming cold snap may not necessarily break daily record lows, as Weather Underground meteorologist Bob Henson pointed out, but it will most certainly be an abrupt change from the aforementioned mild weather lately.

Forecast Lows

There are indications that this colder temperature pattern will last for the eastern U.S. into at least mid-December.
The latest temperature outlook from NOAA's Climate Prediction Center indicates there is a high probability of below-average temperatures in the eastern U.S. during December's second week.

One signal pointing to a continuation of this cold weather pattern is the return of the negative phase of the North Atlantic Oscillation (NAO).
This weather pattern features a northward bulge of the jet stream over the western Atlantic Ocean with a blocking area of high pressure in place near Greenland. As a result, cold air can dive south and lock in across the eastern United States for lengthy periods of time due to an adjacent southward plunge of the jet stream.
The other key feature that is expected to help the jet stream's eastern U.S. nosedive is a strong northward bulge of that jet stream into western North America, known as the positive phase of the Pacific-North American (PNA) pattern.

Now that a colder weather pattern is in place, there will be chances for light snowfall in parts of the Midwest and East through this weekend, but no major storm is forecast at this time. Localized heavy lake-effect snow is also anticipated in the Great Lakes by midweek.
See the link below for more details on the snow potential this week.


https://weather.com/storms/winter/news/2017-12-03-arctic-cold-blast-december-united-states-midwest-south-east