Ingredients of an East Coast Snowstorm
An east coast snowstorm can occur whenever it is cold enough for the precipitation to fall as snow. It is more likely to occur from December to March and more probable in March, or later in the winter season, because the storm track is more favorable to pass over the northeast region of the United States.
East coast snowstorms are more favorable when it is not a La Nina year and when it is in a negative phase of the North Atlantic Oscillation, or NAO.
It is especially favorable when the NAO is negative and trending towards a positive NAO.
A negative NAO acts as a block which slows down storms when they track up the eastern coastline. It also signifies much colder temperatures.
When the Pacific-North American teleconnection pattern (PNA) is positive it causes strong ridges in western United States and troughs in eastern United States. Ridges are associated with pleasant weather, while troughs are associated with stormy weather.
Cold air damming occurs when there is high pressure to our north. With the clock wise flow of a high pressure, it brings in cold air to our area.
A “kissing jet” present at the 300 millibar level, about 30,000 feet or 9,000 meters above the surface, is an indication of a strong storm. A “kissing jet” is when the left jet exit of one jet stream overlaps the right jet entrance of another jet stream.
The “40/70 rule” is considered the ideal track of a coastal storm for producing snow. If a low pressure system passes over 40 degrees North latitude and 70 degrees West latitude, it is indicative of producing a significant amount of snow.
According to the current NAO conditions from the National Weather Service we are indeed in the negative phase of the NAO and is forecasted to trend positive.
Looking at the forecasted 500 millibar map, a strong ridge builds in the west and a strong digging trough builds in the east. In the forecasted 850 millibar map, temperatures are expected to get a lot colder than normal.
The National Weather Service's Climate Prediction Center 6 to 10 day temperature outlook gave New Jersey a 40 percent chance of becoming colder than normal.
Judging from the 500 and 850 millibar map, a major snow storm is possible in the next week or so if some of these factors and dynamics come together at the right time.