Record cold is on the way for Thanksgiving across the Northeast. Temperatures will nosedive below zero on Thanksgiving morning for parts of the region, with temperatures staying below freezing all the way to the coast. Ahead of the cold outbreak, two systems will produce snow in New England. Is it November or January?
This is your Sunday Storm.
The airmass responsible for the Thanksgiving arctic outbreak is currently locked away in eastern Canada with a trough centered over the Hudson Bay. Several shortwaves early this week will drag progressively cooler air toward the Northeast, but the truly bitter air will remain in Canada until Wednesday night, when a high amplitude ridge over the Western North America cuts off part of the Polar Vortex. Each shortwave ahead of the arctic blast will bring with it the chance for snow, although no big storms are on the horizon. The coastal cities along I-95 will likely dodge additional snowfall from these consecutive systems, but a snow event is likely just north and west of the corridor.
A long series of events will unfold before the cold outbreak. The first shortwave will swing across New England Sunday night, however it will be too weak to stir trouble. Slight warm advection from a warm front ahead of the shortwave will supplement the lift from the jet to help generate light rain and snow showers in Pennsylvania, New York, and New England. The snow will accumulate a few inches on the Allegheny Plateau, the Catskills, the Taconics, and the Berskshires. Otherwise only a coating to an inch of snow is expected across Upstate New York, western Massachusetts, and northern New England. Light rain showers will be the dominant mode in central Pennsylvania, the Hudson Valley, and southern New England.
Light snow will transition to light rain with progression of the warm front early Monday morning in eastern New York state, western Massachusetts, southern Vermont, and southern New Hampshire. Cold rain will make for a dreary start to what will soon be a bitter cold holiday week. The rain will melt some of the snow, but one more accumulating snowfall will replenish the snow-pack long before Thursday’s turkey carving.
A much broader and modestly more potent shortwave trough will follow the warm front Monday evening. This system was oriented across the Rocky Mountains Sunday evening and was being pushed eastward by the expanding ridge over the western US. The shortwave will amplify as it propagates toward the East Coast, spawning cyclogenesis in the mid-Mississippi Valley along its cold front as it mingles with Gulf warmth and moisture. The surface wave low pressure will intensify little until reaching the coastal waters of New Jersey/Long Island Tuesday morning.
Precipitation will develop north of the low Monday night from Ohio to the coastal Mid-Atlantic between Monday evening and Monday night. Both rain and snow will fall, mainly impacting the same areas that received precipitation Sunday night through Monday morning. Along and south of the low’s track, precipitation will fall as rain. Weak warm advection here should keep rain relatively light. North of the low, a weak cold surface high pressure system centered over Québec will usher in cold air southward to northern Pennsylvania, Upstate New York, and parts of New England, where the intensifying low will produce a broad region of snow.
Modest frongtogenetic forcing will contribute to the low producing a quick plowable snowfall for parts of New York and New England. A corridor of strong mid-level frontogenesis will setup along the convergence of the cold air from Canada and the relatively warm air from the Atlantic Ocean. The frontogenesis will be strongest between New York’s Hudson Valley and Southern New England. Consequentially, low elevations within this corridor can expect an additional 3-6″ snowfall with peaks of the Catskills and Berkshires likely receiving 4-8″. A very sharp gradient between the two air masses will result in a likewise sharp cutoff in snow totals, with no accumulations expected just southeast of this corridor in most of Connecticut, southeastern Massachusetts, and all of Rhode Island. Cities likely to receive the plowable snow include Hunter, Pittsfield, Worcester, and Concord.
As the low continues to intensify Tuesday afternoon, the heaviest snow will shift to southern Vermont northeastward to southern Maine, where 4-8″ of snow will likely accumulate. Lighter snow will fall northward to the border with Canada. Snow will gradually come to an end Tuesday afternoon in southern New England and Tuesday evening in Northern New England.
Thanksgiving’s frigid airmass will usher in behind Tuesday’s snow. The contrast between the western ridge and the Polar Vortex will support a vigorous jet streak in Manitoba and Saskatchewan. The jet streak will trek southeastward between the upper air systems and drag the Polar Vortex southeastward toward New England between Tuesday morning and Wednesday night. In the low levels of the atmosphere, temperatures will run up to 20°C below normal per the 12z Euro Ensemble (EPS) courtesy of PivotalWeather, representing 2-3 standard deviations below the climatological average.
The cold will have a painful bite. Bitter even for January standards, low temperatures Thursday morning will bottom out below zero across much of New York and New England! That magnitude of cold will be confined mainly to higher elevations, but temperatures of inland locations as far south and east as the I-91 corridor will free-fall into the single digits. It will be slightly warmer in coastal cities of New England, but not by much. Temperatures will tumble into the teens in Boston, Providence and Bridgeport. Temperatures will recover very little throughout the day. Boston is likely to stay in the 20s, possibly making for the coldest Thanksgiving since records began in 1874!
The Polar Vortex cold will match some of the coldest air observed in New England’s climatology for November 22. As illustrated by the NAEFS ensemble from 00z November 18, this extreme cold is quite rare for New England. The extreme cold is forecast to be within the lowest 0.5% of temperatures in the climatology of New England and Long Island. The plot below is courtesy of the National Weather Service.
While the core of the cold will be confined to Upstate New York and New England, Thanksgiving will still be a historically brisk day for the Mid-Atlantic and Midwest. Lows will only bottom out in the 20s, but high temperatures will recover very little. Like Boston, temperatures will likely remain below freezing in New York, Philadelphia and Baltimore. New York City will record its first Thanksgiving below 30°F since 1901, per National Weather Service records. These frigid temperatures will make for only the fourth Macy’s Thanksgiving Day parade during which temperatures fail to rise into the 30s.
The bitter cold will not last forever. Temperatures will rebound during the weekend, but they will still run below normal. The next notable storm to impact the Northeast could possibly develop late next weekend. Be sure to check back with WeatherOptics for updates on the Thanksgiving outlook and on the possible weekend system.