Winter's Last Hurrah...One final Winter Storm Threat in the Books?

Yes we are entering the second week of April, however, we may have a chance for what should be...or hopefully be our final winter weather event of the season. We don't think of April as a wintry month or a snowy month, but it isn't all that uncommon to get snow events in April (especially across the higher elevations). So what is yielding such potential? We'll discuss below! Disclaimer: The graphics below are from the GFS forecast model and I will use the model graphics to illustrate the ideas.

On Monday, April 8, a rather potent piece of shortwave energy is projected to enter the Pacific-Northwest. From here it will continue on an eastward trajectory through the Inter-mountain West and northern Plains. Both the Euro and GFS indicate a rather strong area of low pressure will develop in association with this feature. Forecast models show enough cold air across the northern-tier of the country to perhaps yield a significant winter weather event from ID, WY, CO on east through parts of SD, NE, IA, WI, and MN:

Why do we need to watch this here in CT and New England? This is due to the potential evolution of some major teleconnection patterns which not only support a storm, but support the potential for a cold enough airmass and favorable storm track to at least yield the thought of winter weather.

Moving into the second week of April the consensus is for the North Atlantic Oscillation (NAO) and Arctic Oscillation (AO) to become extremely negative while the Pacific-North American (PNA) becomes positive. Without going into detail on what all this means (this would make this post exceptionally long) the basic answer is...this combination is one that favors a more southern storm track and also for below-average temperatures to spill into our region:

Looking near mid-week next week we'll look at the 850mb level (about 5,000 feet above the ground). I've highlighted a couple features; temperatures, an 850mb low, and a boundary. Across southeastern Canada is a very anomalously cold airmass characterized by temperatures -10°C to -14°C.If the image was forwarded in time a bit it would show that some of this spills into our area. The 850mb low shows about where the potential storm is positioned. The orange line shows the separation between miler air and colder air and this boundary will be key:

As the system gets closer, computer forecast models indicate that we will see a surge of warmer air move into our region and we would not have to worry about winter weather at all, however, given what we are seeing with the NAO, AO, and PNA it's a bit difficult to believe such warm air makes it into our region...it will be very close...IF THIS TRANSPIRES AS ADVERTISED.

As we move through April chances for snow rapidly dwindle. This is due to the increasing sun angle, warming airmass, and lack of available cold, however, if we are going to get snow in April...this is a look you would want to see.

Not saying this will happen, but if the NAO and AO become as negative as forecasted and we see the spike in the PNA...this could get quite interesting...at least somewhere in New England.

Snow Event Wednesday Morning (04/03/2019)

This potential has been in the cards for the past week and while the odds were never very high, these odds have skyrocketed substantially over the past 24-hours. This isn't going to be a major event for many (accumulations will likely be confined to the hills), but it will have a high impact to the Wednesday morning commute...good news though as temperatures quickly warm into the 50's to near 60 during the afternoon.

A vigorous piece of shortwave energy at 500mb will be associated with a very strong area of low pressure just off the coast. The track and strength of the system will help to maintain a rather unseasonably cold low-level airmass over the region. Surface temperatures will be marginal which will reduce accumulations and likely limit them to the hills, however, there is tremendous upward vertical motion associated with this system and that will increase the likelihood for snow falling even if temperatures are as high as 34-35°F:

Let's break it down:

• Rain will begin to transition over to snow (especially in the hills between 2:00 and 5:00 AM Wednesday morning).
• A 3-5 hour burst of heavy snow is possible where snowfall rates could approach 1.5''/hour. 
• Snow will be wet and sticky. 
• Snow ends by mid-Wednesday morning and then temperatures quickly warm into the 50's to near 60 by the afternoon.