MU Met is not about suppression this weekend:
As I mentioned on Saturday, I'm keeping a close eye on Friday and Saturday (Jan. 21-22) for a potentially significant winter storm somewhere in the mid-Atlantic. Details remain nebulous at this distance, and there's a wide range of potential solutions at this time. Anything from an out-to-sea solution to a major snowstorm or another snow-to-rain event is currently on the table. However, I always like to look at these smaller-scale systems from a broader perspective and ask, "What does the large-scale pattern suggest?" In this case, the ridge axis in the West that I so often refer to is still modeled to be right along or just offshore of the West Coast. At the same time, the large-scale, downstream trough axis (or bottom of the dip in the jet stream) will likely be over the Mississippi or western Ohio Valley. This is not too dissimilar from the large-scale setup that was present over the last few days, making me highly skeptical an out-to-sea outcome.
Now, there are going to be several disturbances (associated with the southern branch of the jet stream) that come onshore into Southern California over the next 24-48 hours. At the same time, energy associated with the northern branch of the jet stream will dive down into the northern Plains. This is what meteorologists refer to as a "split flow" jet stream pattern, and these are notoriously difficult to predict more than a few days in advance. The two branches of the jet stream often converge across eastern parts of the US in these types of patterns, and just where, when, and how these two branches interact can mean the different between a major winter storm and nothing at all! Trying to sort out which disturbances are going to interact with one another and in what fashion is challenging, to say the least, more than a few days in advance. So, my point is that, while I currently do favor a solution that results in at least some snow across the Lower Susquehanna Valley and northern Maryland late Friday into Saturday, we're still only talking about "potential." A lot can change in the next 2-3 days, and I certainly wouldn't bet money on any particular outcome! What we will likely have going for us this go around is a cold, Canadian high pressure system centered across northern New England instead of hundreds of miles offshore. This means that north-to-northeasterly winds would be able to funnel cold air down into the Commonwealth before the storm arrives and keep it "locked in" during the event. In last night's case, southeasterly flow off the Atlantic Ocean routed the cold air mass in place and caused precipitation to change over to a wintry mix and rain. At least at this distance, it doesn't appear that we'll have to contend with the same issue on Friday and Saturday. Details will become more clear over the next 2-3 days, so follow @MUweather on Twitter for my latest thoughts and frequent updates!
I'll end by re-emphasizing a point I made on Saturday. Toward the last day or two of January and the first few days of February, our cold, wintry pattern may begin to slowly shift back toward what we saw in December. It sometimes takes a major storm to bring about these pattern changes, so I wouldn't be surprised if there's another storm threat sometime between January 29 (the day I turn the "big 3-0" -- yikes!) and February 1. But, this is just speculation at this point.. so let's deal with one storm at a time and the rest of the chaos sort