This blog is dedicated to explaining meteorological teleconnections.
NAO(North Atlantic Oscillation)
The NAO is the combination of the West and East Atlantic pattern.
A negative NAO builds heights in Greenland, and increases the likelihood of a trough along the East Coast of the United States. The building heights in Greenland, and the trough along the East Coast allows for cold air to funnel down from Canada. During the winter months with the trough along the E.C. the low pressure tracks are favorable for snow as long as the Pacific coroperates(more on this later).
A positive NAO lowers heights in Greenland, and allows the southeast ridge to dominate, and allows for normal to slightly above normal temperatures. With the southeast ridge in place the low pressure storm track cuts inland instead of off the the E.C. This storm track is not ideal for snow.
PNA(Pacific North American Pattern)
The PNA is the observation of heights across the Western and Eastern US.
A positive PNA consists of above normal heights across the Western United States. In response ridging develops over the western states, and in return troughing develops across the eastern United States. For snow across the the eastern states this would be ideal, combined the a -NAO.
A negative PNA consists of below normal heights across the Western United States. In response troughing develops over the western states, and in return ridging develops across the eastern United States. This is not ideal for snow across the east coast, because of the southeast ridging, and storm track to the west of the App mountains.
This teleconnection is an index that measures the circulations over the Arctic. As with other teleconnections the AO consists of a positive phase and a negative phase.
A negative AO consists of above normal heights, and the polar circulation is weak allowing the cold and storm track to be farther south, which in turn allows the cold air from Canada in penetrate into the United States, and the East Coast.
So, an ideal set-up for east coast cold and snow would be a -NAO, -AO, and +PNA.