After a fairly warm December and start to January, signs are finally starting to point towards winter coming back to life. Consistent features in our most recent pattern that have been dominating the United States for the last month and a half look like they are beginning to breakdown, allowing the chances for snow in the east to rise once again. The first big signal we’re tracking is this weekend, where a storm originating from the south looks to meet up with some colder air to the north and produce snow. The question remains, where and exactly how much? With 4-5 days to go still we can’t give any solidified details, but we can start breaking down the general scenarios we’re watching.
There are several pieces to this storm that involve both our southern and northern branches of the jet stream. This complicates things a bit, but also raises the chances for a potential bigger storm system.
Late Friday and into early Saturday our storm system will move from the west to east of the Rocky Mountains and center somewhere over the northern Louisiana – southern Arkansas region. Snow will begin to fall well to the north of our low pressure as our southern stream bends south and allows colder air to seep deeper into the south, and rain or mixed precipitation can be expected in and around the low itself. As our storm taps some moisture from the Gulf of Mexico, heavier precipitation can be expected to develop, both in the form of rain and snow. This much we are quite confident in. It’s what happens next that becomes tricky.
Our southern branch of the jet stream will flatten out a bit, giving our storm the opportunity to possibly interact with the jet to the north. The key to answering whether or not we’re looking at an I-95 snowstorm is how much does our northern jet stream and trough dig, and is it enough to interact with the stream to the south? That crucial interaction would allow our storm system to 1) become stronger and 2) turn further to the north and near the ideal 40/70 benchmark. If this occurs, heavy snow breaks out from Washington DC to Boston and all along the I-95 corridor.
However if the branches of our jet stream remain apart, our storm stays weaker and slides off to the south. This would give light to moderate snowfall amounts to the Mid-Atlantic states, and a glancing blow to many of the I-95 cities. Regardless, chances remain high for accumulating snow from St. Louis to the Appalachian mountains. Anywhere from 3-6 inches of snow can be expected.
This leaves us with two rather distinct scenarios. Track 1 shows the scenario that would ensue with more interaction between the jet streams, and thus heavier snowfall from Washington DC to Boston. Track 2 shows the scenario that would unfold with less interaction between the two jet streams, and thus some moderate snow for states like Virginia, the Delmarva, and places slightly further south –– But nothing big.
Being 4-5 days out, right now we believe that track 2 is more likely. This track has support from the majority of guidance, including some of the top performing weather computer models (The ECMWF and the UKMET). The American Model, and particularly many of its ensemble members, continue to keep us on our toes however, alluding to something more similar to track 1 where many more states to the north are impacted by snow. Until the energy that remains offshore that will eventually produce our storm system comes onshore and is sampled properly by computer model guidance, we cannot be totally sure of anything. In other words, all option remain on the table, with a current preference towards a lower impact snowstorm. Check back tomorrow for more details.