First, let’s look at the overall setup.
It is an incredibly convoluted setup, with multiple pieces of energy. Unlike the blizzard, or even the snowstorm on Friday, there is likely to be even less consensus on what is going to happen. Like Greg said last night, there are known knowns and known unknowns.
1. A period of snow is likely between Monday and Wednesday, as a series of systems impact our state.
2. Accumulating snow is likely, but it is unclear how much will fall.The state will likely see at least one light snow event across the entire state, with the potential for more than that everywhere.
3. With the recent heavy wet snow sticking to trees, especially in eastern Connecticut, any wind associated with this upcoming period could create a higher impact event. We expect a windy period from the pressure gradient associated with the various systems.
The Monday Potential
Like the last system, we are currently looking at three scenarios—a direct hit, a scrape, and a miss as an area of low pressure develops off the Florida coast and explosively develops over the next 48 hours.
The Direct Hit—current odds of occurring: 10%
In this scenario, we essentially relive the events of Friday. The storm that is currently modeled to stay far enough out to see for a miss or glancing blow trends much further west over the next 48 hours, and we get a big hit.
Why this happens: The seasonal trend. The trend for a number of our systems has been to trend northwest at the last minute.
Why it doesn’t: No support. Although some guidance has tried to trend further west recently, there is a lot of ground to cover, more so than the Friday event. It would take an even larger shift for this to be a direct hit—which would be a very large event for Connecticut.
Model support: No reliable guidance shows a direct hit.
The Miss—current odds of occurring: 40%
In this scenario, the storm rapidly intensifies, moves northeast, and just keeps going. Under this scenario, none of Connecticut receives accumulating snow, although windy conditions would still be possible because of the pressure gradient.
Why this happens: The track. The current guidance develops the storm, but it takes a less than ideal track with the low pressure passing well southeast of the 40/70 benchmark we use when we think of big snowstorms for the state.
Why it doesn’t: The precipitation field. With a rapidly developing system, really, one of the strongest all year, the precipitation field expands as develops and passes the region. With the larger scale pattern, having a very sharp cutoff of precipitation looks more unlikely than usual—at least more unlikely it bisects Connecticut.
Model support: The midday run of the European model was a glaring miss for many.
The Scrape—current odds of occurring: 50%
In this scenario, which I currently favor, the system gets close enough to throw back light precipitation that falls on Monday, resulting in a minor to moderate (especially eastern CT) snow event.
Why this happens: Like earlier, the seasonal trend has been to trend northwest over time. Given how far east the system is modeled currently and how soon the system is set to arrive, I am not sure there is enough time for massive shifts to occur. The setup in the upper levels favors slight shifts northwest in my opinion, but it may not make that much of a difference at the end of the day.
Why it doesn’t: The trend is your friend. It was a smart call waiting to post this. Earlier today, there seemed to be a shift toward the west, but the late night runs ended that, with shifts east from the short range, high resolution models we usually rely on at this range. I give a bit more weight to the RGEM than other models outside the euro at this point, and it went east.
Model support: RGEM, NAM, 12z Canadian, as well as the 00z GFS (hot off the presses!) are Take a look at the surface maps from the GFS and RGEM.
There is very high uncertainty in what will happen on Monday. The potential of a high impact event remains low, and a scrape is most likely, bringing the state a period of light to moderate snow on Monday. Snowfall totals would be too speculative to discuss right now given the setup. I would not change my plans based on the Monday potential at this time, but I would keep an eye to updates.
We will provide another update tomorrow when we have additional information.