We’ll be the first to tell you: You’re probably going to see and hear a lot about a potential winter storm over the coming days. In addition to that, you probably shouldn’t take everything you hear all that seriously.
Here’s the long and short of it: Forecast models, over the past two days, have come into agreement on the idea that a significant winter weather event will evolve in the Eastern United States sometime late this upcoming week into the upcoming weekend. A strong low pressure system is forecast to develop from the South-Central United States, through the Mississippi River Valley, and eventually re-develop off the East Coast.
The details of this storm system, including all things from timing, to track, to precipitation totals, remain highly uncertain. This is, for the most part, to be expected at such a lead time. The storm is still, 4 to 5 days from beginning, and the main “players” in regards to the storms evolution are still thousands of miles away. If they do come together as models now indicate, the event could be quite a doozy. But buying into individual model solutions at this range isn’t smart; and borders on irresponsible.
What is causing this storm potential in the first place?
A complicated atmospheric evolution will occur over the next few days, beginning in the Pacific Ocean and ending over the East Coast of the United States. Multiple pieces of energy, from both the northern and southern jet streams, will be involved, as will the Pacific and Subtropical jet streams.
The most important piece of energy comes from the Pacific Ocean, over the top of a Western USA ridge, on Wednesday. Forecast models currently agree that once this piece of energy moves into the United States, it will quickly amplify southeastward toward the Central United States, with a low pressure system forming over the Central US. The exact timing and evolution of this disturbance will have a major impact on how the storm evolves later in the week.
Importantly, this system will be interacting with a northern stream disturbance (Seen above near the Great Lakes) and several jet streams. Currently, models agree that the interaction and phasing will help the associated surface low pressure become quite prolific. After a storm initially develops into the Southeast US and Mid Atlantic, forecast models suggest it will transfer eastward toward the coast, forming a powerful surface low pressure, which could be capable of bringing significant winter weather to the Northeast and Mid Atlantic states.
Adding to the arsenal of this storm system’s potential at this range, is the support of ensemble guidance. The GFS, European, and Canadian models ensemble guidance all show significant support for the storm systems development. However, individual ensemble members show wildly varying solutions. At this range, any individual solution can produce a wide array of sensible weather differences: From rain, to snow, to nothing at all. Still, seeing the ensemble guidance signal the storm threat so strongly at this range certainly raises confidence that the operational GFS, Euro, and Canadian models are not simply out to lunch with the idea of a strong storm system.
What are some of the uncertainties involved?
Anything and everything. At this range, forecast models can often struggle with intricate pattern details and nuances in the atmospheric evolution. Knowing this, it wouldn’t be smart to buy in to any specific solution yet. In fact, it would be quite irresponsible to do so, especially given how often we have seen forecast models struggle with storm systems at a much shorter lead time than this.
Let’s remember one thing: The evolution involves several moving parts. The energy coming ashore from the Pacific won’t be in the United States until Wednesday. Even after that point, exactly how it behaves becomes critical: The northern stream evolution and phasing can completely change the evolution of the storm system. A high pressure to the north, which currently is forecast to keep cold air locked in place during the storm system, remains a major player in the setup as well.
What should we do from here?
As meteorologists, we’ll be carefully monitoring forecast models and ensembles over the next few days for trends and new developments in all of the essential pieces of energy. Watching exactly how the ensemble guidance behaves will tell us much more in regards to how the storm will evolve. Over the next few days, we should begin gaining confidence in exactly what type of hazards the storm will bring, if any, to our area.
Reasonably, right now is a time to begin looking at forecast models a bit more seriously than just “another long range model run”. Let’s be completely honest: What forecast models are signaling today, but operational and ensemble guidance, would be a tremendous winter storm for our area. Still, it’s important to remember that model guidance is just that; guidance for us to use as we attempt to understand how the atmosphere will evolve.
Do yourself a favor over the next day or two. If you see a snowfall map for this weekends potential storm, ignore it. Don’t even bother looking at the numbers. Instead, stay tuned to your trusted sources that take the time to explain both the potential and the uncertainties. Understanding how the atmosphere evolves over the next few days will tell us much more about the storm potential as we move forward.