Stubborn Winter: Yet Another Snow Storm Coming?

And here we are again, just a few days after a previous snow storm, that came only days behind another one.  Each one slightly different, but this one is again taking a slightly similar path, but with secondary development of low pressure likely to become more defined, meaning that a warm tongue would not be as much of an issue.  It most certainly still can, but it’s not as likely to play as big a role with this storm like it did in the last one.

But before that I want to get into the details of the storm or anything like that, I want to give a summary of what I know and what is unknown, and just go over what’s going to be covered in this blog post tonight.

What we know is that this disturbance is coming.  The first piece of associated energy is coming onshore in the Pacific Northwest, and the next piece will move onshore in the next day or so.  This will increase forecasting accuracy, and once we have that better data sampling I will be able to offer up many more details with this storm.  Right now, there are generally two scenarios, one where the confluence over us and blocking in the atmosphere pushes the low pressure far enough south that we only get snow showers and flurries, similar to what we will get tomorrow, and there is not much of a significant storm.  The other one, which I find slightly more likely at this time, is that the storm strengthens and comes further north, far enough to impact the area with the heavier precipitation but not far enough to pull in a lot of warm air.  This could result in moderate or heavy periods of snow (maybe mixed with rain at the immediate coast or just offshore), with moderate to heavy accumulations on Monday.  It’s too early to talk amounts specifically, but I will be discussing what individual models show below for solutions.  So that’s the summary on the storm, and now I’m going to get a little more technical with regards to why I think a storm even this late in March could bring snow to SW CT.

First, I have been mentioning the AO a whole lot recently.  That’s because it is at record low levels, meaning that a direct injection of cold air straight from Canada is happening into the Northeast, hence the ridiculously cold temperatures the last few weeks.  It is approaching a value of -6, something it has not hit since 1985, to put that in perspective.  The NAO is also quite negative, as its current value is -1 but it is expected to drop down to -2 in a few days, again fairly low for March.  The couplet being a combined -6 or -7 is likely some type of record, and what this means is that blocking is ripe for storms to move up the east coast, and that plenty of cold air is in place for this storm.  So while climatology would completely argue against this storm, climatology also should not be weighted very heavily when we are talking about things that have not happened in decades, as climatology is not designed to help forecast for potentially extreme weather patterns.  What is being weighted heavily is the weather models that have been performing the best.  In order, that makes the CMC/upgraded GGEM, ECMWF, UKMET, JMA, GFS, NAVGEM.  Since its upgrade, the GGEM/RGEM has been extremely spot on with weather for SW CT, having correctly called the miss and then wrap around moisture with the storm system two Fridays ago, and then also calling for a longer period of moderate/heavy snow with this last storm.  The GGEM is also one of the most aggressive models with the upcoming snow storm, giving the coast around 6 inches of slush and further inland dumping over an inch of foot with a low pressure system that moves just east of New York City while going through rapid cyclogenesis.  Is this hypothetically possible?  yes.  Do I believe it will be the final solution?  Nope.  The GGEM has always had a bias of over-amplifying storms, and though it has done well recently, I think this could be one it is amplifying a little too much.  This means a weaker storm slightly further south would be more likely, so less snow further inland, but potentially more at the coast as there would be less warm air pulled up.  Most importantly, though, the GGEM shows a lot of moisture with this system, which is what to me screams the most potential.  The GGEM has support from its ensemble mean, too.

Next comes the ECMWF, which is further south than the GGEM and less amplified, but the 12z ECMWF did shift north and gives the region some light snow, and its ensembles are significantly further north than the operational, a sign that a shift north in the operational model is happening tonight.  Historically the most accurate model, should it begin to show a fairly significant storm a lot of people would begin to catch on and focusing in on this storm.  Until then, I don’t really expect that much hype around it.  The ECMWF ensembles are historically the most accurate, though, so it is very interesting that they are north and cold, and I will be looking closely tomorrow morning at what the overnight ensembles bring.  Then, we have the UKMET, which is further south still than the ECMWF, though has not performed very well as of late.  The JMA is similar to the GGEM except slightly less amplified, and amazingly I think the JMA could be the model that stands the best chance of verifying, as it keeps all of SW CT snow with moderate accumulations, but it does not go crazy with a bombing out low pressure.  The GFS, finally, remains fairly weak with the low, bringing only light precipitation to the area as the transfer happens too far out to sea for much more than light snow.  However, the GEFS ensembles support the operational GFS trending wetter, as they showed much more QPF than the operational, a signal that the GFS will likely be bouncing around a lot and is likely to trend stronger and wetter with this storm.  Those are really the only models at this point I’m using for the storm.

That’s really where we stand right now with the storm right now.  I will wait and go into more detail and get more technical tomorrow, but I do want to focus on the 500mb setup and the potential for the storm to stay stronger and trend north.  The potential here screams snow for SW CT, even in late March, and though this may not be a major event, chances are increasing of at least nuisance level snow across the region, if not more.  As always, make sure to keep it here for the latest on the storm.

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