Winter Storm Grayson's Bombogenesis Brought Whiteout Conditions From Virginia to New England, Record Coastal Flooding at Boston Harbor

(MORE: Winter Storm Grayson Southeast Recap | The Science Behind Naming Winter Storms)

Grayson dumped over a foot of snow in a swath from the Virginia Tidewater to Maine Jan. 3-4.

The top snow total was 22 inches near the Etna and Plymouth, Maine.

Islip, New York, picked up 16 inches of snow, with snowfall rates of 2 to 3 inches per hour for at least five straight hours from late morning through early afternoon on January 4. 

Snow fell at the rate of 1 to 2 inches per hour at Newark-Liberty and JFK airports, with winds at JFK gusting over 50 mph. Central Park wound up with 9.8 inches of snow while Queens received 13.6 inches, the highest of the five boroughs.

In New Hampshire, 19.5 inches of snow was measured near Berlin, 15 inches near Seabrook and 13 inches in Concord.

In Maine, Bangor picked up 18.3 inches, Caribou tallied 13 inches, and Portland, Maine picked up 11.9 inches of snow.

(NEWS ROUNDUP: Winter Storm Grayson's Impacts)

Whiteout conditions blasted parts of the Jersey shore, Delaware and the Virginia Tidewater, fueled by wind gusts from 45 to 60 mph.

Parts of southern New Jersey picked up over a foot of snow, including Bayville (18 inches), Cape May (17 inches), Margate City (16 inches) and Atlantic City (14.2 inches at the airport northwest of the city). Drifts to 2 feet were reported in Atlantic County, New Jersey.

A foot of snow fell in Disputanta, Virginia. Norfolk tallied 10.3 inches of snow.

Coastal Flooding Recap

Pounding north to northeast winds worsened coastal flooding along east- and north-facing shores of Massachusetts around the early-afternoon high tide Thursday.

Tidal levels at Boston Harbor topped an all-time record set during the infamous "Blizzard of '78," sending water pouring over the Long Wharf, then surging into streets in the city's Fort Point neighborhood.

Cars were seen floating in a street in Chatham, Massachusetts, after water cut through a barrier island early Thursday afternoon.

Up to 4 feet of flooding prevented the scheduled evening weather balloon launch at Chatham, one of 72 locations in the Lower 48 states where twice daily weather balloon launches provide data for use in weather forecast models.

In Winthrop, Massachusetts, 75 homes were flooded to the first floors and utilities were compromised, according to the emergency management director.

Sea-wall damage was reported and Front Street became impassable due to floodwater in Scituate, south of Boston. A causeway was closed in West Gloucester, north of downtown Boston. Two to three feet of water swamped streets in Nantucket.

Coastal flooding up to the wheel wells of vehicles was also reported as far north as Kennebunkport, Maine, during Thursday's high tide. Tide levels in Portland, Maine, topped out just 2 inches from their record, set in early January 1978. Based on preliminary reports, the highest tide on record was recorded in Bar Harbor, Maine, as well.

Damaging Winds, Blizzard Conditions Recap

Blizzard conditions were met in Bangor, Caribou and Portland, Maine, and on Block Island, Rhode Island. A preliminary statement from the National Weather Service office in New York indicated that several locations over Long Island and parts of New York City, the Lower Hudson Valley and southern Connecticut, also saw blizzard conditions. Several other sites have to be verified by the National Weather Service.

Damaging wind gusts over 70 mph were recorded in Barnstable, Wellfleet, East Falmouth and Nantucket, Massachusetts, as well as on Block Island, Rhode Island, and persistent gusts over 50 mph downed power lines in southeastern Massachusetts and Connecticut.

Wind gusts over 50 mph were also frequent Thursday morning from the Outer Banks of North Carolina to the Delmarva Peninsula. Wednesday night, some gusts over 70 mph were clocked in eastern North Carolina.

Grayson went on to whip Atlantic Canada with winds gusting over 70 mph, heavy snow and heavy rain. 

One wind-prone location on Cape Breton Island, Nova Scotia, reported a wind gust to 106 mph, according to Environment Canada.

Grayson Underwent Bombogenesis

Grayson's intensifying low will track north-northeast off the Northeast Seaboard before plowing into Atlantic Canada into Friday.

This explosive development is what meteorologists call bombogenesis, defined by a rapid drop in atmospheric pressure of 24 millibars or more in a period of 24 hours – criterion that's been well satisfied.

In over four decades-worth of data compiled by Dr. Andrea Lopez Lang from SUNY-Albany and David Roth from NOAA's Weather Prediction Center, this bombogenesis rate of 59 millibars in 24 hours through 10 a.m. EST January 4 was a record magnitude for this part of the western Atlantic Ocean, dating to 1976.

(MORE: Grayson Might Be Strongest Bombogenesis Event Near U.S. East Coast In Over Four Decades)

According to NOAA's Weather Prediction Center, Grayson's minimum estimated pressure was 950 millibars on January 4.

For comparison, past Northeast storms such as Nemo (February 2013), Juno (January 2015) and Stella (March 2017) had minimum central pressures in the 970s millibars.