As we move towards the second half of November, the ingredients for snow will continue to improve with more cold air available and a pattern that will allow areas of low pressure to develop closer to the shoreline. Already this month we’ve seen several smaller systems drop light amounts of snow over the Northeast region, but so far nothing significant.
Tomorrow a storm system will drop down from Canada and begin to develop across the northern Great Lakes, bringing rain showers from St. Louis to Chicago to Detroit. Colder air in the upper atmosphere following behind the system will catch up to the precipitation as the storm slows down around Montreal. Late tomorrow night and early on Thursday, guidance is showing enough energy transferring over to the coast to spark a weak second area of low pressure near southern New England. With cold air continuing to work its way into the storm, snow may become a realistic possibility.
In order to squeeze any snow out of this system for the Northeast though, a few key things need to happen. The first is that the surface needs to cool down. Without an area of high pressure sitting to the north, and the fact that it’s still so early in the season, that’s not very likely. The next thing that needs to happen is a fast transfer of energy. With all the energy to the north, warm air has an easy way of sitting around and floating just as far north as our original low pressure. With a quicker transfer, colder air can more easily seep down from Canada, infiltrate the system, and change the rain over to snow. Guidance like the GFS doesn’t see that happening.
With all of that said though, temperatures are cold enough in the upper atmosphere, and the low transfer just quick enough, that higher elevation and interior snowfall is not so far fetched. We’re not talking any major snowfall most likely, but some wet accumulation is certainly within the cards.
You can see that by Thursday night, our second air of low pressure rapidly develops, and our first area dissipates off to the north. This allows colder air to rush in faster, and higher elevations to changeover from rain to heavy wet snow. With winds coming out of the north over the Great Lakes, some areas of Lake Effect Snow are also likely to develop. Now in this particular scenario, it’s only the highest elevations that see any frozen precipitation.. And even those locations are only looking at a quick inch or two.
One of the reasons we’re being cautious with calling for such little snow, is that all guidance is not in agreement. The ECMWF, often seen as the rival of the GFS, paints a slightly different scenario. Our low to the north weakens a bit faster, transfer is a bit more aggressive, and cold air down to the surface is a bit more potent. The result? A solid thump of snow for interior New England. While the snowfall maps above should be taken lightly (as they don’t perfectly decipher frozen precipitation like sleet and ice from snow), higher elevations across Vermont, New Hampshire, and Maine receive several inches of heavy wet snow Thursday into Friday as opposed to just an inch or two at the highest elevations like the GFS shows.
With only a few days before the actual event takes place, we’re erring on the side of caution and forecasting more of a middle road. Peak elevations should expect to see light snow to rain to a moderate to heavy wet snow, while elevations lower down across the interior are likely to end as a period of wet snow. Our forecast can be found below:
After this storm system passes through on Thursday and Friday, a brief cold shot will move through Friday into Saturday before moderating temperatures during the latter half of the weekend and early next week. Next storm threat comes for Saturday, but is expected to be predominately rain. Stay tuned.