Significant Storm Potential Around February 1, 2021

 There are signals for a rather significant winter storm to begin the month of February. In a winter which has been well...non-existent in terms of the snow department and chances few and far between, it makes monitoring this that much more fun. For us here in Connecticut, there are a wide range of possibilities from a small hit, very large hit, or no hit at all as the storm could miss out out to sea or well off to the south. How the overall pattern progresses through the weekend will determine what type of solution we have.

Since our massive snowstorm back around mid-December two things have been constant;

1) A negative North Atlantic Oscillation (NAO)

2) A positive Pacific-North American (PNA) (however, the PNA has become more negative recently)

Now...typically when you see this sort of combination there are two things you can expect;

1) Colder temperatures

2) Snow...and lots of it

Well neither of these have happened...but we won't get into that here. 

Moving towards the first of February we start to see some changes occur. The NAO trends more positive while the PNA, which has become more negative recently, is expected to become more positive:

When both the NAO and PNA are in this transitory process, this can be a signal for a major East Coast storm. 

The 12z GFS ensemble mean for 500 hPa height anomalies come Monday morning features a very exciting look for snow fans;

1) A ridge across the Inter-mountain West and Great Plains region

2) Trough amplifying across the East with a trough axis into the Southeast

3) A large area of anomalous above-average height anomalies over much of Canada. This will create a "block" and when combined with the look of #1 and #2 sharply increases the likelihood for a storm to develop and either sort of ride up the coast or if it comes from the Ohio Valley, the block should keep the storm farther south and also supply us with cold air. 

One thing we've been lacking all winter is a baroclonic zone off the East Coast. Baroclinicity is a huge driver in cyclogenesis and that has been lacking. 12z GFS forecast temperatures at 850mb indicate there could be a pretty decent barloclinic zone across our area with temperatures about 5,000 feet above the ground to our south as high as +6C with across northern New England they could be as cold as -10 to -12C. This type of steep temperature gradient favors strong upward motion and favorable conditions for low pressure development and strengthening (cyclogenesis):

Forecast models are indicating the potential for energy riding around the crest of the ridge out west digging and amplifying as it moves into the eastern trough. This will be a focal point for the development of low pressure which could rapidly intensify. 

Being nearly a week out, it's way too early to get into details or specifics, however, the signals are there for a pretty significant winter storm which could impact Connecticut around February 1. Details should become clearer moving through the week.