Quick Thoughts on the Tuesday, March 2013, 2018 Snowstorm

One of the most unique aspects of weather is forecasting. Forecasting can be challenging, it can be difficult, it can feel nearly impossible at times, it can be stressful, but in the end it is fun! At least for myself, one of the most enjoyable aspects of forecasting (outside of trying to prepare my readers as best as possible for whatever mother nature has in store) is the learning that takes place during a storm and just after a storm. Every single weather event provides us with a different and unique set-up and each of these set-ups usually comes with surprises. For anyone who is a forecaster the one thing that we must understand and accept is that we will be wrong at times. If you can't accept this forecasting is probably not for you. There are two different types of people out there; there is the type who get very emotional and then lash out and criticism when they are wrong and there are people who take being wrong as a learning experience and they go back, re-evaluate the storm and try to find what they miss. For the forecasters in this second category, these are the ones who are on the path of success or on their way towards the path of success. 

This past storm (while still currently underway!) had numerous challenges from day one. As we drew closer to the storm, forecast models indicated we would likely be dealing with a scenario in which we could see two potentially heavy bands of snowfall across Connecticut which could dump a quite a bit of snow over some towns while areas in between these bands could struggle to accumulate much. When you have a scenario such as this, constructing and presenting a snowfall map becomes quite challenging and this is because snowfall totals are not really uniform across a large area and this leads to sharp and large snowfall gradients sometimes in just a span of a few miles! 

In my blog post from yesterday (http://weatherwiz.blogspot.com/2018/03/accumulating-snows-likely-overnight.html) I discussed the possibility of the two band scenario and discussed what impacts this could have. Well this scenario is exactly what unfolded. Below are a couple screen shots from the radar at 9:43 AM, 10:26 AM, and 1:08 PM. I've highlighted the heavy bands of snowfall:

Notice how elongated and how think/narrow they are. The narrowness of these bands is what makes constructing a snowfall map in these cases a challenge because you just don't know where they will set-up and you don't know how long they will sit in a particular area. In cases like this a difference of even 5 miles can mean the difference between like 4-5'' of snow and as much as 12...15...even 20'' of snow!!! I mean how do you reflect that in a snowfall map? 

Also discussed in the post from yesterday was the term subsidence and how anytime you have a heavy band of snow (sue to extreme upward vertical motion) you must have extreme downward motion (think of the all so popular phrase, "what goes up must go down"). It was discussed that you would have subsidence inbetween the two bands. While forecasting how much snow falls in the areas under the bands and how heavy the intensities are (snowfall rates per hour) is tough, forecasting what will happen in the areas of subsidence is another challenge in itself. In areas of subsidence it can still snow...it's typically very light and doesn't accumulate quickly but this helps to shape the very sharp gradients between a few miles. To give an indication on just how crazy some of the gradients are, here is a tweet sent out by award-winning and NBC Connecticut 's chief meteorologist, Ryan Hanrahan:

Just wild stuff! While forecasters struggle with how to visualize this in a forecast, this is why it's very important to listen to what a forecaster has to say. Often times, the forecaster will explain these situations and try to give as much detail as possible because it's just too difficult to provide this detail on a map. 

Perhaps in the future, as our technology improves and we continue to grow a better understanding of how these mesoscale bands work, we will get to a point where forecasters can confidently forecast exactly where a band (or bands) will set-up and snowfall maps can be constructed to point out where these highest totals will occur and what areas will see much less given subsidence.