This will not be like out typical snow events where we get all the action in a 6-12 hour window but rather the event will be strung out over a period of 36-48 hours and b/c of this, and how the precipitation will come in more wave like everything may not really seem like that big of a deal.
As mentioned in the previous forecast, we will still be dealing with major impacts from this system, especially along the coast where we will have two periods of moderate to major coastal flooding. This will be discussed in more detail below. We will also be dealing with some moderate to significant snowfall accumulations across portions of the region with other parts of the region only receiving light to moderate snowfall totals. More details on this below. We will also have to deal with a period of strong to damaging winds across parts of the region as a tightening pressure gradient and very strong low-level jet just above the surface will help to increase winds at the surface. This will also mean there will be pockets of tree/wire damage as well as power outages. Finally, we will also have to deal with rain, with some getting more than others.
With all this said it's important to know that this is a very low confidence forecast and extremely complex. This forecast will likely bust in several places as it will be nearly impossible to pin everything down correctly given the uncertainties at hand. Also, remember that these totals would be a combination of totals between today and Friday.
Before I get into the forecast specifics I will try to break this down into much clearer details.
First, I would like to discuss the first portion of the storm which will be the affects from the strengthening coastal storm to our south. Currently, the system is affecting the mid-Atlantic and dumping heavy snow on some along with heavy rains. This system will continue working out into the Atlantic where it will begin taking more northerly and then easterly turn so it passes to the south and east of southern New England. Due to strong blocking to our north and strong confluence to our north computer forecast models have had an incredibly difficult time handling this system and it's progression. For days, it appeared that this system would pass well to our south and east and we would have zero impacts at all, then computer model guidance began tracking the system further and further northward and here we are now. Over the past few days computer forecast models have continued to wobble with how far north the system would track, some runs and models showed solutions which gave just about everything significant and even substantial snowfall accumulations. Right now, however, models have actually backed off these types of solutions, especially for western areas as now it is looking as if the storm will track far enough to the south and east to where the heaviest precipitation will occur out across RI/eastern MA. With this said, some of the highest snowfall totals are expected to occur across this corridor. The impacts from this coastal storm will last from now through much of tomorrow and into the first part of Friday, however, b/c the precipitation may occur in more band type features...precipitation will not be consistently occurring this whole period, we will not see extremely substantial snowfall accumulations.
Secondly, I would like to discuss the second feature that will contribute to snowfall accumulations. This feature will be associated with an inverted trough which will develop as a strong piece of shortwave energy moves southwest of our region from the Great Lakes and interacts with the coastal storm to our east. What this will do is draw in moisture from the coastal storm into the inverted trough and shortwave energy and allow for another area of blossoming precipitation and the effects from this will likely be the greatest in areas that are in favorable locations for upslope, usually areas to the east of mountains...or in this case the Berkshires/northwest hills. This feature will have it's impacts felt beginning late tomorrow afternoon lasting through Thursday night and into the first part of Friday.
Breaking those two features down what makes this snowfall forecast so complicated is the fact that 1) We are still unsure of exactly how close to southern New England this system will end up tracking, which will have a substantial impact on how much precipitation spreads into the region and into western sections and 2) Where this inverted trough feature sets itself up...that is a major question right now and is always very difficult to pinpoint until you're within 24-hours and sometimes not even until you're within 12-hours.
Now to go into detail about the impacts:
Coastal flooding:
Coastal flooding may end up being the worst portion of this system, even if the affects are only on a small percentage of people. There will be two periods of moderate to major coastal flooding, one around and during the high tide cycle on Thursday morning and then the other around and during the high tide cycle on Friday morning, and Friday's coastal flooding threat is expected to be much more extreme than Thursday's. While coastal flooding is likely across the immediate coastline of CT on the shores facing Long Island Sound, coastal flooding is expected to be the worst along the Atlantic Ocean facing beaches along eastern MA and the Cape. This is where coastal flooding will be much more serious. Some areas right along the immediate coast here could be under as much as 3-4' of water. This will pose a major threat to any structures along the immediate coast as well as pose a threat to life for anyone who is caught in the flooding. If any evacuations are ordered anyone in the evacuation area should take the warnings very seriously and take the proper precautions...again this is for ANYONE along the immediate coastline ONLY.
Snowfall:
While initially precipitation will begin as rain, which has occurred for many already, although some locations with higher elevation have seen snow, everyone except the outer Cape will transition over to snow later this afternoon and evening. Areas along the outer Cape may see a mix of rain and snow or perhaps even a quick period of snow. As of now, boundary layer temperatures are fairly warm for many but as the system continues to strengthen and winds continue to flow in from the northeast, colder air will drain down and this will eventually lead to the transition of rain to snow.
There are likely to be two maxes of higher snowfall totals, one from extreme northeastern CT to much of RI extending northeastward into portions of eastern MA and then another just to the west of the Berks and into the northwest hills of northwestern CT.
Snowfall may be on the wet side but shouldn't be extremely wet or heavy. Snowfall ratios should be along the lines of 10:1...maybe a tad higher but lack of strong lift and upward motion in the best snowgrowth zone may inhibit greater snowfall ratios and rates.
Rainfall:
As mentioned, initially many will start off as rain and light rain, however, the heavier rainfall totals will occur out across the outer Cape area where warmer air will inhibit much in the way of snowfall accumulations across this area. Rainfall totals may reach or exceed 1-2'' in spots.
Strong winds:
The strongest winds are expected to occur out across eastern MA/RI/SE CT where the pressure gradient will be the strongest. Across these regions, winds could become sustained as high as 25-40 mph with wind gusts as high as 55-60 mph. This will lead to pockets of tree/wire damage and will lead to scattered power outages across the region. Elsewhere, winds will be sustained from about 15-25 mph with wind gusts as high as 35-45 mph leading to isolated tree/wire damage and power outages. Elevations at and above 1000' can expected stronger winds/gusts.
Below is what to expect for snowfall totals and keep in mind this is for between now and Friday so it's possible any snow that falls early then having the snow stop could also melt so in reality in could seem like alot less fell than what really did.
Snowfall forecast:
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