It is no secret that winter has been rather lackluster up to this point, and many of you are probably thinking: "Will there ever be a decent snowfall for the Mid-Atlantic and East Coast this year?". It's hard to believe it, given how bad the pattern has been since January for cold and snow, but there are some upcoming signals in the pattern that give hope for some wintery weather before the season is over. Before we dive into what to expect going forward, let's take a look at why it's been mild and snowless for many of our clients this winter so far.
Image Courtesy of NOAA
The image above shows what the Jetstream pattern has been since the middle of January, and it's easy to see why many haven't been seeing snow. The big elephant in the room is that strong ridge of high pressure over the eastern half of the country. However, it's the central Pacific ridge that has been causing this to occur, which is very common later on in tyical La Nina winters. As a result, the Western United States has been seeing a majority of the winter fun, as troughs have been in place for much of their winter. This is pretty much the exact opposite of what you want to see in a pattern for cold and snow in the East. This pattern for the east is on par with the warmest and least snowiest winters on record. Something in this pattern is going to have to change for any hope of snow. The question is: "What features currently shown in the above image will change, and how will they change?".
A stratospheric warming event occurred last week, where temperatures in the stratosphere warmed up significantly from initially being on the colder side. This allowed the polar vortex to weaken dramatically and get displaced from its previous location over the North Pole. Impacts from these events usually take a few weeks to be felt at the surface with staying power. More will be discussed on this later, but we believe this has an immediate impact on the pattern.
Image Courtesy of Tropical Tidbits
The image above shows the upper air pattern that we expect for the rest of February. You may notice that the Polar Vortex is more pronounced over central Canada. This will allow transient cold shots to impact the Midwest, Mid-Atlantic, and Northeast. There are actually two threats of wintry weather the rest of this month to go with these cold snaps. However the Upper Midwest, Great lakes, and New England are favored to see most of the snow and ice, while the heart of the Ohio Valley through the Mid-Atlantic see rain. Why is that? Well, there is still no real block in place to stop the southeast ridge from bringing mild air north and forcing the storm track north and west of the Mid-Atlantic. There may be cold air available in Canada, but this is simply not enough for the Midwest and Mid-Atlantic to see snow.
OK, so what has to happen for this to change? Well, the only factor that can bring a prolonged period of wintry weather to the Midwest, Mid-Atlantic, and Northeast is this stratospheric warming event that we mentioned earlier. Stratospheric warming events can be game changers for the overall weather pattern, but pattern changes from these things are never guaranteed, as a few things need to happen:
1. Modeled warming in the stratosphere needs to actually verify.
2. These events are location dependent, as WHERE the warming occurs is very important for any given location.
3. The effects of stratospheric warming need to make it down to the troposphere for impacts on our sensible weather.
The point is: No two stratospheric warming events are the same, which will talk about below:
Image Courtesy of Tropical Tidbits
The image you see above shows what the pattern is like well up in the stratosphere, which is where the polar vortex of our interest is located. This is showing the warming from several days ago. So clearly, this event verified. As you can see, however, all the warming happened over the western and central parts of Canada, which forced the main polar vortex to go into Europe and even parts of Asia. This is not what you want for a sustained pattern change to more wintry weather, as Europe and Asia will be the areas that benefit from this. Going forward, the models continue to keep the polar vortex (in the stratosphere) for these areas and eventually just collapse it all together. We saw a notable polar vortex displacement, but not a true split, which has different results.
To compare this with previous warming events, there was a major stratospheric warming event back in February of 2018. This ultimately led to a cold/snowy March and April from the Midwest to the Northeast. As you can see below, that event was pretty different from the one we're dealing with.
Image Courtesy of NOAA
Back in 2018, the warming happened over Asia and Europe, which is a much different story from what just happened this year. Ultimately, it led to a split of the polar vortex, which allowed a major piece of it to go into Canada, and resulted in significant high-latitude blocking (-NAO) for the month of March.
Great, so in our event, Europe and even Asia look to be the ones that benefit this time around, if the warming couples down to the troposphere (which seems likely). This means that most of our clients across the Northeast would likely miss out on a sustained cold and snowy pattern early on in March. Usually, when Europe turns cold, it is not until a few weeks later that the cold makes it to the Eastern United States. For this to happen, high-latitude blocking would have to develop. These types of stratospheric warming events can lead to high latitude blocking, which has some growing support. With that said, if blocking were to develop, it would likely wait until the second week of March for any sustained cold to make it east. If we were to make it to that point, the pattern would likely last a few weeks before breaking down late in the month.
In terms of impacts, snow chances would increase for many, but the favored areas still remain in The Great Lakes and New England. The trough out in the Western United States does not look like it wants to give up its crown. That means, the Southeast ridge will still try to come north at times despite this blocking. That will make it tougher for the Ohio Valley and Mid-Atlantic to see snow, but the chances in these areas are certainly a bit better than they have been all winter.
One of our seasonal analogs that we currently like is the 2016-2017 season. That was a very similar winter to this one, as much of the mid-Atlantic saw very little snow through February. There was a major winter storm that finally brought significant impacts to the Mid-Atlantic in mid-March. We are not saying that a repeat of that will happen, but don't let your guard down yet for a possible repeat March surprise before we transition into Spring!
