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The GFS model is starting to indicate some changes to this very mild late fall weather pattern. November was the 5th warmest on record in Central Park. The model indicates a front will produce rain later this week and then a weather "clipper" system from the Great Lakes may produce some rain or snow showers this Saturday night or Sunday morning across the NYC metro area. Then next week a storm is forecast to develop over the Southeast and then track northeastward. But in keeping with the weather patter so far this month as well as for November, there is no cold high pressure in place to the north so that this will be primarily a rain event for the NYC metro area. A huge high pressure system plunges into the western half of the nation by next Thursday and Friday (often when the east is mild and west is cold). On Friday (December 23, 2011) low pressure over eastern Canada will drag a long cold front (with a very long latitudinal trough extending from eastern Canada to FL at 500 mb) across the eastern seaboard with mild air in place this will produce rain across much of the NYC metro area with cold air moving in behind the front on Christmas Eve, there could be a brief change to snow across the interior with flurries for NYC. Christmas Day looks to be dry across much of the nation with two hugh high pressure systems dominating most of the country. By the afternoon of December 26, 2011 there is practically no precipitation forecast anywhere in the US. A much different scenario than last winter when the huge Blizzard of December 26, 2011 was dumping more than 2 feet of snow across most of the tri-state region. The weather across the Northeast looks relatively dry and seasonably cold after the 26th through New Years Day. The only potential storm is forecast to move well south off the Southeast coast on December 29-30, 2011.
The North Atlantic Oscillation (NAO) remains in a highly positive phase with no blocking over Greenland. This positive NAO produces a westerly storm track and milder air with mostly rain across the Northeast. A weak La Nina is in place this winter which is expected to continue to extreme drought in TX with drier than normal conditions across the southern third of the nation including FL through February. Above normal precipitation is forecast through February for the upper Plains and the Great Lakes, normal precipitation is forecast for the Northeast. Temperatures with this La Nina pattern are forecast to be below normal for the upper plains and Great Lakes with below normal temperatures for the southern tier of the country. Normal temperatures are forecast for the Northeast. The NAO is trending to be less positive later this month and the last few 500 mb forecasts indicate a strong Icelandic Low which normally will pull down colder air into the lower 48 states. I would therefore expect to see the milder than normal weather continue for the rest of December with colder weather for the first half of January here in New York City.
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.
