Quick Update on Storm Chances Next Week

For my eastern U.S. readers, I figured I'd do a quick update here on the possible storm chances next week, specifically with the larger storm that has been showing up on computer model forecasts for late next week. Recall from yesterday the idea was that unless the northern brach of the jet stream slowed down, it would be tougher for the pattern to amplify, or "slow down" enough to allow a larger storm to develop. I did cite a couple of reasons why this could occur, one being the stratospheric warming recently, which has weakened the polar vortex, and the other being shifts in the tropical Pacific Ocean, which in technical terms, is leading to an increase in global angular momentum, which typically builds up as circulations slow (this can include the jet stream here in North America... It doesn't always happen this way, but can "stack the deck", so to speak). I have the angular momentum tendency below:

Focus on the bottom graph. You can see a spike up in the last week or two, but it is waning now. Computer models today still show the storm, but shifted well north of where they had it. This is a common adjustment especially with bigger storms, as stronger storms tend to form farther north anyway. But also the drop shown in today's angular momentum update may be a sign that hey, the jet stream isn't going to slow as much. That seems to be the message from today's models as well, as features across the north are shown moving along quicker and thus the storm isn't able to "dig" as much as previously indicated. The curious thing though is that models still show it blowing up into a strong storm, albeit farther north. I say curious because I would have assumed a quicker exit due to the faster northern stream, and a weaker low pressure as a result. This still gives me quite a bit of uncertainty with how this plays out. I certainly don't think anyone in the Northeast is out of the running with this yet. Down into the Mid Atlantic it's going to be tough, as you cannot ignore the trend of today's modeling, which matches the trend of the season for storms to generally trend north as time rolls on. I think the "la nina" tendencies of the pattern this winter have been the major culprit in this.

We'll see how things look tonight and tomorrow. If we can keep the "blocking" pattern that we have out in the North Atlantic / polar regions (which tries to keep colder air in place in the eastern U.S.), then this may not be the last chance for some winter fun, though it is getting late the farther south you live. Problem is timing how long until the block breaks and it is game over and we warm up (maybe a week or so into March?).