Except for an outside shot of a bit of sleet or snow on the front end of the rain Monday night, the rest of December seems warm and snowless.

Take a look at the current position of ridges and troughs in the northern hemisphere:

For one thing, the positive Arctic Oscillation has been replaced by a big fat ridge over the pole stretching into Greenland. Ridging over Greenland corresponds to the negative phase of the North Atlantic Oscillation, a pattern infamous for its association with major east coast snowstorms. In addition, the troughing on the west coast has been replaced with a ridge, allowing colder air to flow into the east.

Although this represents just one model run, it is not alone. Several models for days have been hinting at this change and we believe it will happen, for a variety of reasons. For one thing, the stratospheric polar vortex is predicted to weaken, which corresponds to a -AO and -NAO pattern in the lower atmosphere. Also, the El Nino and associated tropical convection is weakening and shifting west allowing the pattern in the pacific to become more favorable for cold/snow. To top it off, the southern jet stream is coming to life, which will help feed moisture into potential snowstorms.

We can’t say for sure that this winter will be a blockbuster, but all signs are that our fortunes are going to change shortly! For those of you enjoying the current warm weather, I can offer the following: even with this shift, it is unlikely that temperatures will approach the icy depths of last winter– expect more average temperatures going forward but many more chances for snow.

Merry Christmas and Happy Holidays!