The leading edge of this system is just now pushing onto shore as you can see from the enhanced infrared satellite image below. I've placed a low where the system is currently located. You can see the counter-clockwise circulation quite well.
The last of the models that were hanging onto a more norther track have now went south. In fact, the trend is to push this low into the Gulf of Mexico by Christmas. I think over the next couple of model runs overnight and into early tomorrow morning, we'll get a much better feel of this system - simply because of the increased data points to be entered into the equations the model relies on to produce the maps. There will be much more data available on this system now that it is on shore.
As I mentioned yesterday, the models are in disagreement as to how the northern and southern tracks of the jet stream will go and when they will phase together. I've looked at a lot of model runs over the past two days and it seems that the trend is to take the low into the deep south and phase the two jet streams over the Atlantic Ocean before the storm moves up the east coast and turns into a noreaster for the New England area.
You'll recall from yesterday's post that some of the older model runs were taking the low into Tenneesee and Alabama and some forecasters are still holding out to that option. But I disagree. I think that's too far north for a number of reasons. For starters, there is a blocking high situated in Canada at the 850mb level. That is forcing everything to the south. Secondly, the low coming on shore right now is just too far south to make it much farther north and overcome that blocking high. It would really need to be moving on shore in mid-California to overcome this and take a Tenneessee/Alabama track. Thirdly, based on the latest model guidance, I don't think the two waves of the jet stream will phase together until late Christmas day over the Atlantic Ocean. Amd there will not be enough energy and momentum to shift it north until that happens. Over the ocean is too late to take it north into our area!
Here's a visual idea of what I'm talking about. The model run on the left is the GFS 0Z run (7pm last night). Notice that it takes the low right over New Oreleans. To the right is the GFS 12Z run (7am today). Notice that it takes the low even further south over the Gulf of Mexico and slows down the timing quite a bit.
I think the low will eventually turn out to travel somewhere in the deep south near the Gulf. And frankly, I don't think it will have much of an effect on our weather. The mositure that you see in our area on these two models is actually from a dip in the northern section of the jet stream in our area and there just isn't enough precipitable water associated with that stream to be able to produce much in our area. Consider the latest snowfall map from the GFS 12Z run:
This seems more on track with what I'd expect from just a small upper-level distrubance from the jet stream in our area. This takes us at about 2 inches of snow by Saturday. With the low largly out of the picture for our weather, I really think we'll see less than 3 inches total with this storm and I think that the 1-2 inch range is a much better bet. I do think we will see something and I do think it will make travel rough for a while. I still expect it to start late Friday afternoon or evening. If you are planning to travel on Friday, take caution and stay tuned as the days get closer. I'll blog more about this tomorrow as more model solutions come out.
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