December 5–6, 2020 nor'easter

December 5–6, 2020 nor'easter
	GOES-16 satellite imagery of the rapidly deepening nor'easter impacting New England at 14:19 UTC (9:19 a.m. EST) on December 5
Type	Extratropical cyclone; Winter storm; Nor'easter; Blizzard; Bomb cyclone
Formed	December 4, 2020
Dissipated	December 8, 2020
Highest winds	1-minute sustained:; 75 mph (120 km/h);
Highest gust	105 mph (169 km/h) at Mount Washington, New Hampshire
Lowest pressure	976 mb (28.82 inHg)
Maximum snowfall; or ice accretion	Snow – 18 in (46 cm) at Carrabassett Valley, Maine
Maximum rainfall	2.62 in (6.7 cm) at Newport, Rhode Island
Fatalities	None reported
Damage	> $25 million (2021 USD)
Power outages	> 280,000
Areas affected	Southeastern United States, Northeastern United States, Atlantic Canada
	Part of the 2020–21 North American winter

The December 5–6, 2020 nor'easter brought heavy snowfall, hurricane-force wind gusts, blizzard conditions, and coastal flooding to much of New England in the first few days of December 2020. The system originated on the Mid-Atlantic coast late on December 4. It then moved up the East Coast of the United States from December 5–6, bombing out and bringing heavy wet snow to the New England states. It brought up to 18 inches (46 cm) of snow in northern New England, with widespread totals of 6–12 inches (15–30 cm) farther south.

The nor'easter caused over 280,000 power outages, mostly in Maine, in addition to causing several injuries.^[3] The system is estimated to have caused at least $25 million (2021 USD) in damage.^[2] It was unofficially named Winter Storm Eartha by The Weather Channel.^[4]

Meteorological history

The nor'easter originated as a weak frontal system over Alabama late on December 4.^[5] Several hours later, the system began to grow more organized, transitioning into an extratropical cyclone over North Carolina by 03:00 UTC on December 5.^[6] The developing low-pressure exited the coast 6 hours later, with a minimum central pressure of 1,000 millibars (30 inHg).^[7] After this point, the nor'easter began to undergo bombogenesis, reaching an initial central pressure of 984 millibars (29.1 inHg) off the coast of Rhode Island at 18:00 UTC that day.^[8] After making landfall in Nantucket 3 hours later with a central pressure of 981 millibars (29.0 inHg),^[9] the low-pressure strengthened further, reaching its peak intensity of 976 millibars (28.8 inHg) at 06:00 UTC on December 6 off the coast of Maine.^[10] After slowly weakening for several hours that, it made landfall in New Brunswick at 18:00 UTC with a central pressure of 984 millibars (29.1 inHg).^[11] The system weakened slightly over New Brunswick, but began to weaken faster after emerging into the Gulf of Saint Lawrence.^[12] At 21:00 UTC on December 7, the weakening nor'easter made landfall in Newfoundland with a central pressure of 992 millibars (29.3 inHg).^[13] After this point, the low-pressure began to rapidly weaken, with the system dissipating inland over Newfoundland the next day.^[14]

Preparations and impact

Winter Storm Warnings were issued on December 4 and 5 in advance of heavy, wet snow and possible blizzard conditions across New England, including both Boston and Portland. Winter Weather Advisories were issued further south, and High Wind Warnings were placed into effect on Cape Cod in anticipation of hurricane-force wind gusts.

Southern New England

In Connecticut, near-whiteout conditions were reported for prolonged periods on December 5, leading to numerous crashes on interstates. I-84 was closed in both directions from Tolland, Connecticut, to the Massachusetts state line for hours as a result of numerous crashes and a lack of snowplows.^[4]

Massachusetts State Police lowered the speed limit to 40 mph on I-90 at noon on December 5 due to ongoing whiteout conditions on the roadways. A crash was reported on I-90 in Millbury a few hours later, prompting the closure of two lanes. Over 1,800 snow removal vehicles were deployed in Massachusetts to clear roads of snow and ice. Over 26,000 power outages resulted in Massachusetts, and several thousand of those were not restored until the next day. Dennis recorded a wind gust of 68 mph (109 km/h) on the afternoon of December 5.^[3]

Northern New England

In New Hampshire, Mount Washington recorded the second-highest snow total during the storm with 17.9 inches (45 cm) falling there and the highest wind gust during the storm, with a peak wind gust of 105 mph (169 km/h). The state recorded over 60,000 power outages, and most were not restored until December 6 or 7.^[3]

Carrabassett Valley, Maine, recorded the highest snowfall total during the storm, with a total of 18 in (46 cm). Meanwhile, Cranberry Isles reported sustained winds of 70 mph (110 km/h) during the height of the storm. Maine also had the highest number of power outages, with 210,000 customers being put without power and some outages lasting for days. Much of Maine also faced whiteout and near-blizzard conditions for prolonged periods of time, resulting in numerous crashes on roadways.^[3]