The first half of Winter has been extremely active across the eastern half of the United States with a blizzard that kicked off the new year and multiple snowstorms between December and January. With the brief thaw this weekend (that still ended with a snowstorm for the interior Northeast), is Winter finally taking a break?
It doesn’t appear so – Or at least remains unclear at the moment. Over the last week, our computer model guidance has hinted at the potential for another coastal snowstorm that could impact the major cities along the I-95 corridor, but as always, there has been a lot of flip-flopping and struggling. Just as we’ve seen with our recent past threats, this entire setup relies on the energy and pattern at 500 mb in our upper atmosphere. In order to get a snowstorm to come to fruition, we need a good ridge in the west (higher heights with warmer weather), and a deep trough in the east (lower heights with colder weather). When we see this general pattern, there’s an increased chance lobes of energy can phase together and create a large storm.
Above is the overall setup we’re looking at for the early and middle portion of this upcoming week – We do have some ridging out west and a decent trough in the east, but as you can see, there are complications. For one, out west we’re watching a possible short wave (lobe of energy) that could help flatten our ridge, and make it harder for the energy in the east to come together. Remember, the more amplified ridging we have out in the west, the deeper the trough will be in the east, and the more likely we are to get our energy to phase. Our trough not only has to dig deep enough, but also has to tilt negative early energy to draw in the energy to the north. Guidance has struggled and continues to go back and fourth on the tilt and depth of our trough.
In summary, if we can have our short wave out west slow down or weaken and allow our ridge to amplify, we can get a deeper trough in the east that has a better shot at tilting negatively, and thus bringing our two short waves together faster. The faster they come together, the closer and quicker our storm forms along the coastline. We highlighted the possible differences in low positions above based on whether or not we get phasing.
Taking a look at guidance off of weathermodels.com, last nights run of the ECMWF (00z) was close to producing a major snowstorm, with the shortwave out west weaker allowing our ridge to still remain mostly intact, while the trough out east digs enough to bring our two lobes of energy very close to each other with partial phasing. The result is moderate snow along the coast and heavier snow very close by:
The image above is valid for overnight on Wednesday and into early Thursday, and you can see light to moderate snow spreading from Washington DC to Boston to New England. Now the most recent run of the ECMWF, along with most other global guidance, shows the second scenario – This is where the lobe of energy out west is strong, the ridge is weaker, and the trough digs less.
Notice here how much further apart the lobes of energy are in the east, resulting in very little phasing and a storm much further offshore. The lobe of energy in the west isn’t stronger per say, but digs much further south, and shunts our ridge much more than the previous run of the ECWMF. As a result, most of the storm remains weaker and offshore:
You can see here that pretty much all of the snow remains away from the coast, keeping the I-95 corridor cool and dry. Some light snow reaches extreme southeast Massachusetts and Maine. Where do we go from here? Just as we saw with our previous storms this Winter, guidance has GREATLY struggled in the mid-range, making it hard to say the most recent solution from our models is the final one.
What we need is for all these pieces of energy to be sampled before making any type of official call, which won’t happen for another few days. Once that energy is integrated, it’s possible we see guidance go back to a more aggressive solution with snow along the east coast. Until then, much of this remains up in the air, but is well worth keeping an eye on. Check back tomorrow for more.