If you watched your favorite local news program last night, you probably saw the Meteorologist throw up his/her hands in uncertainty regarding the snowfall forecast for tomorrow’s nor’easter.   And while we are less than 12 hrs from the start of the event, confidence is still very low when it comes to snow, however, there are still some aspects of the forecast that I am confident in.

Tomorrow a storm system is going to develop south of Long Island.  It will become quite intense.  It will be slow moving and will very likely perform a loop south of Nantucket.  Strong easterly-northeasterly winds will allow for a lot of Atlantic moisture to fall over the region.  Much of it falls as rain.  Some of it will fall as heavy wet snow.  The coastal flooding will likely be the most significant impact from this storm.

Timeline

Presently an area of low pressure is drifting eastward through the Ohio River Valley.  By 7 pm tonight it will nearing the Ohio-Pennsylvania border.  Heavy rain will be falling across much of PA with heavy snow on the northwest side along the shores of Lake Erie and western New York.  12-18″ of snow is expected east of Buffalo.

7 pm Thursday – TropicalTidbits

During the overnight hours, the primary area of low pressure will begin to lose its energy and a new secondary storm center will begin to develop east of Atlantic City, New Jersey.  Batches of heavy rain will enter Southern New England from southwest to northeast between 8 pm and midnight.  Most locations outside of the higher elevations in the Berkshires start as rain.

1 am Friday – TropicalTidbits

By Friday morning the new storm center south of Nantucket has taken over and heavy rain and strong gusty winds have over spread the region.  The higher elevations in the Berkshires are fighting to hang on to snow, but ultimately may flip over to rain as well.  Heavy snow is fall across much of New York where 12-18″ is expected west of Albany.

7 am Friday – Tropical Tidbits

Now comes the trickiest part of the forecast.  As the storm center loops south of Nantucket and massive amounts of moisture are fire hosed in off the Atlantic, the atmosphere is working to cool itself off and transition from rain to snow.  Elevation will play a key role in just how early locations change to snow.  The Berkshires flip back to snow first, followed by the Worcester Hills and higher elevations in southwestern New Hampshire.  Best estimate is that the flip to snow occurs sometime between 12-2 pm in these locations.

1 pm Friday – TropicalTidbits

During the late afternoon and evening hours the rest of Southern New England should flip over to snow.  The lower elevations along the coast and in the river valleys will be last to do so.  Snow will fall heavily for a period of time.  The snow will be heavy/pasty in nature.  Combined with strong wind gusts, power outages are possible.

7 pm Friday – TropicalTidbits

Eventually the storm center drifts far enough southeast and the fire hose of moisture off the Atlantic begins to die down. Precipitation will end from northwest to southeast overnight Friday into Saturday with the Cape and Islands hanging on the longest.

1 am Saturday – TropicalTidbits

By Saturday morning things have quieted down across Southern New England as the storm center drifts further out to sea towards Bermuda.

7 am Saturday – TropicalTidbits

 

Tides/Coastal Flooding

Coastal Flooding Concerns – NWS Boston

Of all the potential impacts from this system, the coast line is in the most danger.  Back in January, the “Bomb Cyclone” brought with it a storm surge during high tide that broke the Blizzard of ’78 high water mark in Boston Harbor.  That was for a single tide cycle for a relatively quick moving storm system.

Tomorrow’s storm is going to be quite strong with northeasterly winds that could be of hurricane force pushing water up against the coast line.  Because the storm is so slow moving, it is expected that multiple high tide cycles will be impacted.  In fact, due to the wind direction, the water from the first tide may not ever recede and a “low” tide may not be experienced.

Also different from the “Bomb Cylcone” is going to be the magnitude of surf just offshore pounding the coast.

Potential Wave Heights – NWS Boston

Oh……and its a full moon.  Meaning the tides are already high; as evidenced by the inundation by today’s high tide in Scituate.

High Tide, Scituate, MA – Chris Gloninger NBC Boston

Wind

With any strong nor’easter there is the potential for power outages due to tropical storm to hurricane force wind gusts.  Tomorrow’s storm will be no different.

Potential Max Wind Gusts – NWS Boston

Heavy Rain

Remember, most of this storms precipitation falls as rain.

Potential Rain Totals – NWS Boston

Heavy Snow

Before I get to my snowfall forecast, I want to talk about the potential this system has.  The top analog for this event is the April 1, 1997 Blizzard.  More commonly known as the April Fools Day Storm.  A lot of similiarities exist here.  Strong storm south of New England starting as rain with cold air attempting to work its way in and end as snow.  During April 1, 1997, rain flipped to snow about 8-10 hours earlier than expected.  The end result:

4/1/97 Total Snowfall

But what the heck is going to happen tomorrow?  If anyone has any confidence, they are lying to you.  Can I leave it as 0-24″ for everyone?  Probably not.  Therefore, the snowfall forecast map below is the best I can figure in terms of snowfall from this system.  Note: The ranges are wider than normal.  Thus highlighting the lack of confidence.

Storm Total Snowfall

-Chris


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