I have to apologize for the lack of updates during the past week or so, but I have been very busy with other activities; however, I do want to briefly review why the threat of the previous winter storm for 1/15-1/16 that I highlighted last week didn’t pan out.

Below is the GFS model from this past Friday afternoon. You can see a developing low pressure over eastern North Carolina, which subsequently moved northeast to a position off the New Jersey and New England coast over the next 24 hours. A near perfect track for a major east coast snowstorm. This track was dictated by the favorable upper air pattern I discussed in my previous post.

So if that’s the case, what the hell happened? The fly in the ointment was in fact the low seen over the Great Lakes, originating from the northern jet stream, which not only stayed separate from the coastal low, but was also rather strong, allowing for warm air advection to scour out the cold air that was in place just 24-36 hours prior to the image below. This low and the lack of a strong cold high pressure to our north, made things just a little too warm, and instead the result was a quick hitting, cold rain for most, with the exception of the central and northern New England high country and particularly Maine. As stated previously, while the kitchen was open and the menu set (in other words, a favorable upper air pattern), what comes to the table (at the surface) isn’t always what you expect.


That being said, why is there a much bigger threat on the horizon for later this week into this weekend? Because the scenario which caused the rain instead of snow for the last storm will be completely reversed.

Below are the overnight ensembles from the European, Canadian, and American (GFS) models, which are basically a mean of numerous individual runs averaged together.




You can see all are in rather good agreement for, what at this time looks to be a rather long duration winter storm, located off the east coast in the Friday through Sunday time period later this week. But what is important this time around is the fact that cold air will be in place prior to AND during the storm, thanks to a nice cold high pressure anchored to our north and west, as depicted on the GFS operational model from last night:


This high will, if modeled correctly, will supply the cold air needed for a major winter storm (at least several inches of snow) for much of the east coast from Virginia north to at least southern New England.

Of course, the key phrase is, “if modeled correctly.” There IS rather remarkable agreement among the ensembles and operational runs this time around, something that has been lacking this winter so far. However, we are 5-6 days away, and it can’t be stated with any certainty that this storm will come to fruition. That being said, I do like the setup, both aloft, and, as illustrated above by the presence of high pressure to our north, at the surface. One thing that does concern me a little this far out is the overall strength of the subtropical jet and the models underestimating this strength early on. You can see how the overnight individual European ensemble run low placements are clustered primarily near and to the west of the mean:


Given this look and the strength of the subtropical jet, I wouldn’t be surprised if the storm overall creeps north and is modeled a little stronger in the next few days. This will introduce more warm air as you go farther south and east particularly along the coast. Successive runs of the  GFS ensembles from from yesterday evening through this morning (18z, 0z, 06z) showed this:

18z GEFS:gfs18zens

0z GFES:gfsens1

6z GEFS:GFSens

You can see the mean low placement is stronger and farther NW on the latest run (06z) versus the two previous runs (18z and 0z). I will say that the GFS has actually been performing better than the European in the last few runs regarding consistently with this storm, which is somewhat of a rarity, but, surprise, it does happen sometimes.

Bottom line, it’s still 5-6 days away, but the setup is a good one, with cold air available this time around, and there is rather good model agreement. I will be waiting until at least Tuesday 1/19 before I become more confident something big is coming. The potential is certainly there, but given the rather fickle nature of the models and complexity of the pattern, things can still fall apart.

More as we get closer presuming things remain favorable….



This entry was posted in Lehigh Valley Weather Blogs. Bookmark the permalink.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s