Over the last several days we’ve discussed the possibility of a coastal storm rapidly developing parallel to the eastern seaboard, and shifting far enough west to impact much of the I-95 corridor with heavy snow and strong winds. While this still remains a “thread & needle” type of event where small changes could have huge implications on impacts, it’s becoming more clear this evening that at least a significant portion of the I-95 corridor will be affected by a powerful snowstorm.

Over the next 24-48 hours, energy will gather from the southern Plains and northern Plains, beginning to interact late tomorrow. These two separate short-waves of energy will likely phase, at least partially, and create an incredible amount of moisture and energy off the southeast coastline tomorrow morning and afternoon. Within an 8-12 hour time block between 7 AM and 7 PM tomorrow, we’ll likely see our storm drop 10-20 millibars in pressure before potentially fully phasing energy together tomorrow night, dropping an ADDITIONAL 15-25 millibars. This is what the meteorological community refers to as bombogenesis, which is any storm that drops 24 millibars of pressure within a 24-hour period. Our storm tomorrow will certainly be able to achieve that, and likely much more.





As we mentioned above, our storm really starts to get going as the sun rises tomorrow morning across the southeast. This aspect of the storm is perhaps the most shocking, as we anticipate frozen precipitation to start the day off across northern Florida. Yes, we’re talking about the sunshine state located in the far southeast corner of our nation. It’s likely that between 6 AM and 10 AM tomorrow morning, a mixture of freezing rain, sleet, and snow breaks out from Tallahassee to Gainesville, reaching all the way towards Jacksonville. While it will only last for a short time, it could become potentially heavy, dropping a coating to as much as an inch of icy slush across the region. Much of this area is under a rare WINTER STORM WARNING, which has not happened for northern Florida in nearly four years.

As we get into the afternoon hour, our storm will begin moving northward, spreading a heavy wintry mix and snow to the coastlines of Georgia and South Carolina, another relatively rare occurrence. Cities like Savannah (GA) and Charleston (SC) could be looking at a period of wintry mix and snow between 10 AM and into the mid and late afternoon hours. It’s possible that from Charleston on northeastward, we see an extended changeover to snow that leads to light (possibly even moderate) accumulations.

Heading into the evening and overnight hours, snow will begin moving into coastal and central North Carolina, where several inches of the white stuff is anticipated to accumulate. Areas furthest northeast will most likely see moderate snowfall amounts, possibly adding up to near half a foot in some isolated locations.

Overnight and into the early morning hours of Thursday our storm really begins to deepen offshore. Guidance is suggesting that our blizzard could reach pressure down into the 960 mb range by the time the sun rises on Thursday.  At this point, low position and location of our northern stream of energy will be crucial in determining where the heaviest axis of snow ends up. The further west that both the low pressure and northern stream of energy end up, the better shot we have at extending the precipitation field further west. The earlier runs of the NAM model were hinting at things trending this way, but unfortunately with so much waffling and disagreement, we may just have to wait until the storm begins to have a final answer on where the sharpest cutoff and heaviest snow falls.





While the above images of the NAM aren’t the most recent, we posted this as an example on Twitter today of how the northern energy stream impacts the cutoff of the precipitation field. Once again, we cannot stress how crucial this is in determining where the heaviest snow sets up. On the left we see last night’s run of the NAM with much LESS separation between the northern stream energy and main low pressure, and as a result, the precipitation shield is much LESS expansive. On the right hand side is this morning’s run of the NAM, which shows the northern energy stream much further back to the NW, leaving more “breathing room” between the low and the energy, and thus allowing the precipitation to push much further inland.

This ALL takes place beginning overnight Wednesday and early Thursday morning, when snow finally makes it up to the northern half of the I-95 corridor. We expect snow to start moving into the DELMARVA and southern New Jersey area after 1 AM on Thursday morning, and then push into the Philadelphia and New York City metro area within an hour or two of 5 AM. The rest of southern New England and coastal northern New England will get going between 7 AM and 11 AM on Thursday, before the whole region is covered by the early afternoon. It’s also at this time that snow will begin winding down across major cities like New York and Philadelphia, making it a quick-hitting, but quite powerful event. Again, the further off to the east you are, the better shot you have at higher impacts.



Areas further to the west from Raleigh to Washington DC will only get scraped by the storm, maybe squeezing out a quick coating or an inch. Further east from Dover (DE) to Trenton (NJ) to The Big Apple, a period of heavier snow and gusty winds will allow between 3 and 5 inches of snowfall to accumulate, with isolated spots of up to half a foot. Again, while totals won’t be very high, gusty winds and bitter cold temperatures will make for a brutal condition on Thursday. Moving even further east now into Long Island, coastal CT, eastern MA (including Boston) and up into New England, we expect a much stronger and more prolonged event, with 6-12 inches of snowfall likely away from the extreme east, and then 1-2 feet possible from near Boston and up into a good chunk of Maine. Not only will totals be high, but winds will be vicious, and temperatures will drop rapidly after the storm passes. We’re also concerned about any ice that has formed close to the shore across the Cape and SE MA, as rough seas and strong winds may try to send some of that inland, making for an even more dangerous situation. By Friday morning, the storm will have completely gone, but temperatures will continue to stay low with winds still gusting out of the north and northwest.

Now with all of the above said, we can’t stress enough that this is STILL very much a fluid situation, meaning that small changes in the northern energy stream, in the speed of our southern energy, and in the track of our low pressure system, could bring a lot of these heavier totals further west. We’ll have a final and more definitive call on this tomorrow morning.

Much of the focus of this storm has remained on the precipitation, but wind will be a big issue as well, especially with the size and magnitude of this storm system. 



Along the immediate coastline from just north of Charleston to just east of The Capital, wind gusts will get into the 30-40 mph range during the peak of the storm. However, once you start getting into coastal NJ, southern New England (including NYC and Long Island), and then on up into Boston and eastern New England, we expect peak wind gusts to be over 40 mph at times, and possible closer to 50 mph at the height of the storm. As you head into the extreme eastern ends of New England (The Cape and coastal Maine), it’s possible we get a few gusts close to 60 mph or higher, which could cause a lot of issues in addition to the heavy snowfall. And if you thought that was crazy, hurricane force wind gusts remain JUST BARELY off the US coastline, making any slight shifts in the track of the storm a big deal. Wind gusts will be over 85 mph close to the center of our storm system.

The good news is that, apart from New England, this storm is a relatively fast mover and should be out of our hair by Friday morning. The bad news is, when and where the storm does hit, it will hit hard. Blizzard conditions for the northern part of I-95, ice and snow down to Florida, winds gusting close to hurricane force, and bitterly cold temperatures to follow will likely make this storm one to remember for quite a while. The next big story after this? A shot of cold air even chillier than this past one.. 2018 coming in like a lion!




Author

Currently leads business development and forecasting across all sectors and is the Founder and CEO. Pecoriello founded WeatherOptics in 2010 as a blog called, Wild About Weather, which quickly gained a following. He also launched an app in 2013 called, Know Snow, designed to accurately forecast the chances of school closings.

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