(Premium) Upcoming storm has many possible solutions

While we currently are basking in clear skies and chilly northerly winds, the main talk in the meteorology community has been on the potentially  large storm system to affect the eastern half of the US between February 23-25. A few days ago, there was pretty significant model agreement on the storm and the general details — which is quite surprising given the lead-time. Not surprisingly, this agreement has completely reversed and now we have wildly different solutions on every model, all of which have validity.

Let’s get to it.

While we will have a zonal weather pattern this weekend,  a powerful Aleutian low will be pumping up some strong ridging into the western half of the US and into British Columbia. This sets the stage for potent shortwaves traveling down from Canada and entering the US, and their interaction could turn into a powerful storm somewhere in the Mississippi Valley. This ridging will also force plenty of cold air to form in south-central Canada, which could get tapped into our storm — but it also may get bottled up there. That is one of the many major questions that we have with this storm system: the degree of cold air that gets drawn in. The storm in the Mississippi Valley strengthens as phasing between multiple pieces of energy occurs, and it then attempts to head up the coast. Secondary energy trailing the parent storm could try to turn this storm into two waves: one on late February 23rd – February 24th, and another one on February 25th.

The process all starts on Sunday night into Monday, when a sneaky clipper system will be forming in the Midwest and trek towards our area. Now, there will not be a lot of cold air around, as this weekend looks to be pretty mild, so this clipper most likely will just bring some rain showers. However, with the cold air being built in Canada, it would not take much for some colder air to work its way in. While the flow remains pretty compressed during the clipper, the clipper may still be able to strengthen enough to tap into the colder air from Canada and drag the frontal boundary further south. This could be enough to give some areas NW of NYC a couple of inches of snow, while coastal areas end as snow showers.

The ramifications of this could be significant. If this storm can drag the frontal zone and cold air further south, then the storm for next week has a higher chance to be colder as well. If not, then the storm looks to be warmer. The 12z GFS, for example, shredded this clipper out and it did not have much of an effect on the pattern. Thus, the frontal zone and cold air remained further north, and rainfall moved into a decent chunk of the Northeast on February 24th. The GGEM, on the other hand, was stronger with the clipper and tapped into just enough cold air for there to be a hit of significant snow with the same wave, before a changeover to rain. The UKMET completely amplified the parent system and gave rain for everyone. The European was strong enough with the clipper to shift the frontal zone southward enough to have the first wave miss our area entirely. Then a secondary wave began to form.

While the 12z GFS was much warmer than the Euro with the initial wave, it was similar to the Euro in that it had trailing energy forming and interacting with the storm. Also, notice how in the above image, there is a small ridge in Quebec. That helps lead to an area of high pressure at the surface, which allows temperatures to crash and for rain to change to snow. The trailing wave helps precipitation to re-blossom and then linger over the area long enough for several inches of snow to fall. This is just one possible solution, but it is advertised on both the GFS and the Euro, though the Euro did not have any rain at the start.

On the above image, notice the isobars hanging back. That is a sign of the trailing wave interacting and causing a secondary area of deepening pressures. This ends up essentially acting as its own storm, which allows for a good period of snow.

The question is, does the pattern overall support snow? Well, yes and no. Let’s take a look at the GFS ensemble mean valid for next Tuesday.

The GFS ensembles certainly show what was mentioned before: the strong Aleutian low and downstream very strong ridge in the West and British Columbia. The negative heights in the Mississippi Valley are where our storm is forming. There is also some ridging into Greenland, which looks like a -NAO. However, that is somewhat deceiving, which is why this pattern — while it could certainly support snow — is not necessarily a great one for snow. The reason it’s deceiving is because one of the main purposes of a -NAO is to hold a 50/50 low in-place. That keeps high pressures in optimal positions in SE Canada and prevents troughs from amplifying too quickly. But on the above map, there is no 50/50 low at all. If there is no true 50/50 low to hold-in place to begin with, then there is not necessarily a purpose of the -NAO to begin with, which means it does not really help us get a snowier solution. Instead, we have a very strong ridge in the NW Atlantic, which would tend to lead to high pressure in that region. That means warmer air tries to flood in and any storm that forms could try to cut/get pushed inland. The aforementioned clipper system being stronger and pushing the frontal boundary further south could certainly help halting the warm air advancement, but it may not necessarily be enough on its own to do so.

To be fair, this -NAO is not a bad thing for snow: it can still help push a few features south and compress the flow enough to prevent an inland runner; but it’s just not as beneficial for snow-lovers as usual. Thus, warmer solutions with a high pressure escaping off the east coast are certainly possible. This is why we are not jumping the gun on snow at this time. Of course, the Pacific pattern is still very good and if the interaction/phasing with the trailing wave is timed correctly, a secondary area of high pressure could return and cool us down enough to see snow. So it’s not a bad pattern for snow, either, and it certainly has the potential to bring us some snow. But a messy interaction with the trailing wave could send the storm further east and make the storm less impactful. Then again, a delayed initial wave and a faster trailing wave could mean the energy gets more consolidated into one bigger storm, which could be a major snow event for a lot of people.

Perhaps it’s best to just say that almost all options are still on the table with this one.