'Marathon' storm to bring wintry precipitation back to Northeast

The stage is set for a sprawling area of heavy snow and dangerous ice from a cross-country storm that could produce horrendous travel conditions across the interior Northeast from Thursday into Friday, AccuWeather meteorologists say.

Boston and parts of the New York City and Philadelphia metro areas will be at risk for slippery travel conditions even as the storm departs at the end of the week.

"The storm is a marathon, not a sprint," AccuWeather Senior On-Air Meteorologist Justin Povick said, referring to the extended duration of a massive storm and its wintry precipitation that may last as much as 48 hours over the Central and interior Northeast states.

The storm that was well underway on Wednesday in the central United States is actually a double-barreled feature with the first part being the warmer of two systems that will go on to impact the central Appalachians and mid-Atlantic to central and southeastern New England.

The warming trend that began on Tuesday continued into Thursday in most coastal areas as temperatures soared into the 40s and 50s F along much of the Interstate 95 corridor of the Northeast. Above-freezing temperatures also occurred well inland into the mountains, before temperatures fell below freezing in those areas on Thursday night.

A mix of snow, rain, freezing rain and ice can be seen on radar tracking through the Northeast Friday morning. (AccuWeather)

The mild air will result in all or mostly rain that began in the mountains on Wednesday night to expand to the upper mid-Atlantic and New England coasts on Thursday. In areas with large piles of snow left behind from the recent blizzard, the combination of melting snow, rain and blocked storm drains can lead to street and highway flooding. Where the ground remains cold, some surfaces can be icy, especially those that are untreated and shaded from the sun.

Widespread stream and river flooding is not anticipated since rainfall amounts are not expected to be heavy enough and snow will not melt rapidly enough. However, the recent cold weather caused a significant amount of ice to form on some waterways. The milder conditions will cause some of that ice to break up in parts of the central Appalachians and in central and southeastern New England. There can be sudden water level rises, where ice becomes jammed up. However, ice-jam flooding is likely to be isolated. A quick return of cold air will also keep the risk limited to a short duration.

As the first of the two storms in the double-barreled system moves off toward southeastern Canada and a second storm arrives across the region, a press of colder air will cause rain to change to snow and ice from northwest to southeast across the central Appalachians and much of New England from Thursday to Friday. In northern New England and northern and western New York state, a wintry mix that developed Wednesday night transitioned to snow by Thursday.

Because the anticipated track of the second storm has shifted southeastward, the corridor of heaviest snowfall accumulation has also trended southeastward since the start of the week. A zone of 12-18 inches of snow will extend from the southern shores of lakes Erie and Ontario to central and Down East Maine.

Cities such as Cleveland; Erie, Pennsylvania; Buffalo and Syracuse, New York; Montpelier, Vermont; and Augusta, Maine; have an excellent chance of picking up a foot of snow from the long-duration storm.

"An AccuWeather Local StormMax™ of 30 inches is most likely to occur in the Adirondack, Green and White Mountains in the region," AccuWeather Meteorologist Brandon Buckingham said.

As heavy as the snow is forecast to be in that swath, most road crews are well-equipped and prepared to handle the situation. However, ice is another matter, and there is a zone in the Northeast that has the potential to experience a significant storm in that respect.

The area most likely to experience enough freezing rain and sleet from the storm to make for dangerous travel conditions will stretch from east-central and southeastern Ohio through a large portion of Pennsylvania to the Hudson Valley of New York and Massachusetts. Travel along portions of interstates 68, 70, 79, 80, 81, 87, 88, 89, 90 and 99 may not only be hazardous but also extremely dangerous as temperatures dip and road surfaces become icy from Thursday night to Friday.

The icy build-up risk zone includes the Pittsburgh, Williamsport and Wilkes-Barre/Scranton, Pennsylvania, metro areas, as well as Poughkeepsie, New York, and Worcester, Massachusetts. People in this part of the Northeast should be prepared for regional power outages. A potential saving grace for part of this zone will be the fact that some areas will experience more sleet than freezing rain, which is the greater hazard, or the chance of a quick transition from ice to snow. But, where sleet does not take up a substantial part of the ice storm, a glaze between 0.25 and 0.75 of an inch can build up on trees, power lines, roads and elevated surfaces.

A small accumulation of ice and snow is anticipated in parts of northern West Virginia, southeastern Pennsylvania, northern New Jersey, the lower Hudson Valley of New York and southern New England by Friday, leading to slippery travel.

Regardless of the amount of snow or the duration of a wintry mix of precipitation, temperatures will take a plunge during the latter part of the storm and in its wake. Where power outages occur some neighborhoods could be in the cold and the dark for an extended period.

For example, around Pittsburgh, temperatures plunged through 20s F on Thursday night as the storm continued. Temperatures may fail to rise much at all on Friday in the Steel City, only to plummet to near 10 degrees during Friday night.

Areas of slush and standing water will freeze as the Arctic air takes hold. Snowfall on top of an icy mix could be glued down, making it difficult to remove by Friday night and Saturday morning. AccuWeather meteorologists recommend that property owners and road crews clear and treat sidewalks, parking lots, streets and highways before the freeze-up occurs.

Rain will be the primary form of precipitation for Washington, D.C., Baltimore, Philadelphia, New York City and Boston for both storms, but with a caveat. In Boston, there is little doubt that the second part of the storm will end as a wintry mix that transitions to a bit of snow on Friday. It is the speed with which precipitation will transition into a wintry variety that is uncertain in Beantown. Other questions remain about how quickly surfaces may become icy in New York City and if that will happen at all in Center City Philadelphia, Baltimore's Inner Harbor and around Washington, D.C., on Friday.

CLICK HERE FOR THE FREE ACCUWEATHER APP

"In the New York City metro area, you do have to respect the fact that we are talking about a large city which holds more heat than surrounding locations," AccuWeather Senior Meteorologist Dave Dombek said. Dombek noted that the transition to icy conditions may not occur immediately at the start of the day, nor wait until evening, and is likely to be somewhere in between.

Around New York City, elevated surfaces north and west of the city will be more prone to becoming icy early in the day, while areas in Manhattan and on Long Island, New York, will tend to be the last to potentially ice up, forecasters say. A bit of sleet may fall at the tail end of the storm and could increase the chances of slippery conditions.

Around Washington, D.C., and Baltimore, there is a greater chance of heavily traveled roads drying off in the wake of rain that falls Thursday night into early Friday, but motorists and pedestrians should be on guard for icy spots to develop, especially to the north and west as the day progresses. Conditions could be substantially different for commuters heading home toward the normally colder suburbs later in the day, compared to the ride into work.

In the wake of the storm on Saturday, temperatures may approach the freezing mark around Philadelphia and sneak above freezing in Washington, D.C., but areas farther to the north and west are expected to remain locked into the Arctic air and temperatures in these areas will plummet under a clear sky Saturday night. Lows Sunday morning will be below zero F from the northern tier of Pennsylvania to northern New England, forecasters say.

AccuWeather meteorologists will also be monitoring the progress of a sneaky southern storm that could take a northward jog later this weekend. That storm track has trended farther south over the past day or two, bowing to the extent of Arctic air in the Northeast, but there is still some room for a shift once again. People in parts of the Carolinas and southeastern Virginia should keep an especially close eye on the storm if they have travel plans on Sunday as the chance of snow and ice in that region is not zero percent.

For the latest weather news check back on AccuWeather.com. Watch the AccuWeather Network on DIRECTV, Frontier, Spectrum, fuboTV, Philo, and Verizon Fios. AccuWeather Now is now available on your preferred streaming platform.