****Major winter storm from central Plains to Mid-Atlantic with significant snow, disruptive ice…watch for “cold conveyor belt” snow on the backend...late week/weekend storm threat****

(Left) As a cold conveyor belt flows westward in the cold air mass north of a mature mid-latitude low's warm front, it splits into two tributaries. One tributary curves clockwise away from the low's center and eventually ends up flowing eastward. The second, more important, tributary turns counterclockwise around the low, coiling cyclonically around its center. (Right) The cold conveyor belt associated with a mature mid-latitude cyclone carries moisture back into the cold air northwest of the low. The combination of ample moisture, cold air, and upward motion can create heavy snow northwest of the low's center.

Credit: David Babb, Penn State University/College of Earth and Mineral Sciences

Overview

Low pressure will intensify over the central Plains on Sunday and it will become a major winter storm with widespread impact as it treks eastward reaching the coastal waters of the Mid-Atlantic region by Monday night. This system will produce significant snowfall along the way with more than a foot in many areas and there will be a swath of disruptive ice immediately to the south of the heavy snow zone. In addition, there will be an enhanced risk of severe weather on Sunday in the storm’s warm sector over the Lower Mississippi Valley region. The storm arrives in the Mid-Atlantic region late Sunday night and precipitation can last all the way into Monday night in some sections thanks in part to the likely development of “cold conveyor belt” snow on the back end.

A major winter storm will move eastward from the Central Plains to the Mid-Atlantic region producing a long stretch of significant snow along its path. Map courtesy NOAA, tropicaltidbits.com

Central Plains to Ohio Valley

Low pressure will intensify on Sunday over the central Plains and begin a trek to the east and with cold air well established on its northern side, heavy snowfall will break out from Kansas to Ohio. Some of these areas can receive more than a foot of snow from this winter storm – the heaviest for some in over a decade. Winds will increase markedly as well on Sunday resulting in blizzard conditions over the central Plains with whiteout conditions making travel extremely hazardous.

This same winter storm will produce a lot of sleet along its path in addition to the significant snowfall. Map courtesy NOAA, Weather Bell Analytics

Significant icing is in store for some parts of the central Plains, Middle Mississippi Valley region, and parts of the Ohio Valley with a combination of sleet and freezing rain. This too will result in dangerous road conditions in many areas and power outages are definitely a threat with some areas likely to accumulate as much as a quarter-inch of ice.  

Freezing rain will also big an important factor with this upcoming major winter storm system and ice accumulation can lead to numerous power outages along its path. Map courtesy NOAA, Pivotal Weather

Mid-Atlantic impact

The surface low pressure system is likely to push through the state of Kentucky on Sunday night and snow will break out in the Mid-Atlantic region. The snow is likely to arrive in West Virginia, western Virginia, and western Maryland during the evening hours and then after midnight across the DC metro region. Snow will continue its advance and likely reach into the Philly metro region just before daybreak assuring Monday AM commute issues in the DC-to-Philly corridor. At this point, the advance to the north of the snow shield will be somewhat inhibited by dry air stationed over the Northeast US. As such, the storm’s effects will likely be considerably more limited in places like New York City with less snow expected up there as compared with Washington, D.C. and Philadelphia.

The forecast map for Monday evening shows a lot of snow in the storm’s northwest (cold) sector. This “cold conveyor belt” snow can produce additional accumulations on the backend of the storm in the DC-to-Philly corridor prolonging the event into Monday night. Map courtesy NOAA, tropicaltidbits.com

On Monday, snow will continue at varying rates in the DC-to-Philly corridor and sleet is quite likely to mix into the picture; especially, across the southern half of the DC metro region and from there to the Delmarva Peninsula and southern New Jersey. Any sleet that falls would cut down on snowfall accumulations and this looks like it could be a factor in some areas, for example, like the southern sections of the DC region. Given the dry air mass currently locked in across the Northeast US, a quick reduction in snowfall amounts is likely to set up somewhere between Philly and New York City. However, there is certainly still the chance that this “snowfall gradient zone” shifts to the north somewhat as the lack of strong high pressure over New England allows for this kind of last minute shift of the precipitation shield to take place.

“Mesoscale” or small-scale snow banding is likely to take place in the Mid-Atlantic region during this upcoming storm system and the area of strongest “frontogenesis” (shown in orange, blue) may be just the location for these heavy snow bands to occur…something we’ll closely monitor. Map courtesy NOAA, Pivotal Weather

“Cold conveyor belt” snow on the backend

By Monday night, low pressure will become positioned just off the Mid-Atlantic coastline having traveled all the way from the central Plains in a general west-to-east movement. Given the location of the surface low pressure system at this time and its counterclockwise flow of air surrounding it, cool and moist ocean air - just to the north of a warm front - is likely to be transported westward and “lifted” as it moves into the cold air sector to the north and west of the low…traveling along the so-called “cold conveyor belt”. This process helps to create the “comma-shape” appearance to the cloud pattern in mature mid-latitude winter storms (and sometimes to the radar echoes as well). This “cold conveyor belt” snow is also referred as “wrap-around” or “backlash” snow and it can be quite productive with respect to additional accumulations on the backside of the storm. Bottom line…watch for some backend accumulating snow in the DC-to-Philly corridor and over the Delmarva Peninsula prolonging the storm into late Monday or Monday night and it can actually develop after a lull in the precipitation.

Preliminary snowfall estimates:

DC metro region:

5-10 inches with isolated higher amounts. The higher amounts in that range should take place on the northeast side of the metro area and lower amounts to the southwest (i.e., Montgomery and Howard Counties (MD) should receive more snow than Fairfax (VA)…expect sleet to mix in as well; especially, across southern sections of the area.

Philly metro region:

3-6 inches with the higher amounts in that range on the southwest side of the metro area and lower amounts to the northeast (i.e., Chester and Delaware County should receive more snow than Bucks County)…sleet may mix into the picture; primarily, across Delaware and southern NJ.

New York City region:

A trace to a coating.

Note: the location of the heaviest precipitation amounts can shift slightly to the north (or south) from current thinking and this potential shift can make a big difference in given areas with respect to snowfall totals.

This unfolding cold and active weather pattern can result in snowfall across the Deep South and just such a threat can take place by the end of the upcoming week. Map courtesy NOAA, tropicaltidbits.com

Looking ahead to a late week/weekend storm threat

This cold and active weather pattern is likely to produce another significant storm late next week in the Friday/Saturday time frame (1/10-1/11) and this one will develop much farther to the south over the Gulf of Mexico as compared with tomorrow’s storm formation over the central Plains. This late week system could produce snow in portions of the Deep South as cold air will penetrate way down into that part of the nation during the preceding few days. There is a chance this system then pushes to the north and east…potentially bringing more accumulating snow to the Mid-Atlantic region.

January is looking like a wild month.

Meteorologist Paul Dorian
Arcfield
arcfieldweather.com

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