Extreme Temperature Contrast Across the US Now...

There is a very intense temperature contrast now across the nation with temperatures plunging below zero again across the Rockies and upper Midwest. Temperatures will plunge to 7 degrees in Santa Fe and 25 degrees in Las Vegas.  Lows tonight will be near -7 in Denver, -13 in Bismarck and as low as -21 in western Wyoming.  Meanwhile in the east tomorrow, the temperature will rise to near 60 in Washington, DC and 48 in Portland Maine.  Heavy rain and thunderstorms continue to produce flooding in the Tennessee and Mississippi River Valleys with up to 3 inches of rain expected.  Snow, sleet and freezing rain is falling today in northern Indiana and southern Wisconsin. 
The GFS model continues to indicate a strong flow across Canada with a vortex at 500 mb remaining as it has been the last several weeks over central Canada.  This pattern has resulted in keeping cold, Arctic air to the north.  However, the last few days, a highly amplified flow has allowed for the cold air to plunge into the western parts of the country.  From my experience over the years, when it is unusually cold in the west, it is normally unusually warm in the east and that is what is happening at the present time.  Temperatures will be 20 degrees above normal with highs in the 70s and 80s across the Deep South. 
La Nina is currently in place in the Pacific as it was last season.  The NAO and AO indices have become strongly positive over the last week.  Latest GFS forecasts indicate a trend that will turn both indices negative in the next two weeks.  The positive phases of these two indices normally result in milder weather along the East Coast with fewer coastal storms that produce snow. We have had very little snow in New York City since the 4.7 inches of snow that fell on November 7-8, 2012 only a week after Sandy.  Only 4/10 of an inch of snow fell in Central Park in December 2012.  Only a trace of snow has fallen so far in Central Park this month. 
The GFS model is indicating that the Great Lakes and the Northeast will have more seasonable winter-like conditions next week through the end of the month.  No coastal storms are forecast, however there are indications that fast move "clipper" systems may race across the northern tier of the nation after next weekend. 
George Wright is a Certified Consulting Meteorologist for Wright Weather Consulting, LLC. George is also a meteorologist with ABC News and Cablevision News 12. Our website is WrightWeather.com.