Boston, the newly-minted capital of Canada and inspiration for Disney's Frozen, is in the path of an approaching storm system this afternoon that threatens to drop up to two feet of snow on the city and surrounding areas by sunrise on Tuesday. To the south, New York City could see an icy mess as a result of freezing rain.

The Setup

The low pressure system in question is moving across Michigan at this hour, and snow will begin to pick up across the Northeast as it approaches the area. The heaviest snow will ramp up as the low transitions into a nor'easter overnight tonight and through the day tomorrow, with the worst accumulations falling—where else?—on coastal New England from eastern Massachusetts through southeastern New Hampshire.

The storm won't be terribly cold, so the freezing line will be an issue in some spots. NYC and surrounding areas should fall on or around the freezing line, which will create a unique set of issues for the city. The atmospheric setup could lead to a period of freezing rain across the area, making travel (by car or on foot) on untreated surfaces hazardous for a time on Monday.

Snowfall Accumulations

Here are the latest snowfall forecasts from local National Weather Service offices across the Northeast, as seen in the Enhanced Data Display. Snowfall totals jump around a bit from office to office as a result of different offices coming to slightly different conclusions, but much of the region will see a widespread double-digit snowfall from western New York to the coast.

The specific total noted on the EDD in Boston (16 inches) is lower than the 18- to 24-inch range that NWS Boston paints on its website (pictured at the top of this post), but either way, the metro area will likely see a significant snowfall that exceeds one foot.

The Weather Channel, which does a great job when it comes to forecasting (except for that name), somewhat disagrees with the National Weather Service's assessment of the storm.

The Atlanta-based weather behemoth predicts 12 to 18 inches of snow across the Boston area and one to three inches around New York City. This is a little different from the National Weather Service's forecast, which gives the NYC area a dusting (if that). It also pulls the heaviest snows back away from the Buffalo area, while dropping Boston's snowfall range by six inches.

Ice Accretion

Areas that won't see significant snowfall aren't out of the woods when it comes to this system. An influx of warm air aloft will filter into the storm as it comes through the area, creating the very real threat of freezing rain across vast parts of southern New York, Pennsylvania, New Jersey, and Connecticut.

The National Weather Service expects a glaze of ice across areas shaded in pink, with up to one-quarter of an inch of ice in the darker pink around the New York City metro area. Any ice accretion is dangerous to drivers and pedestrians (think black ice), and tree damage and power outages become a hazard once ice accretion reaches one-quarter of an inch or more.

Freezing rain occurs when snow falls into a pocket of warmer air aloft and completely melts into a liquid raindrop as it descends through the layer. If air near the surface is cooler than this pocket of warm air—with temperatures at or below freezing—the raindrop will become supercooled and freeze on contact when it touches any exposed surfaces like streets, sidewalks, stairs, railings, cars, and trees.

Records

Last week's blizzard set records across the Northeast, with Boston seeing its third-largest 24-hour snowfall on record (22.1 inches of snow in 24 hours) and Worcester seeing its largest snowstorm on record after the blizzard produced 34.5 inches of snow in the city.

Over the past 30 days, Boston has seen 50.6 inches of snow, not including the four inches that the airport saw in this morning's snow. If the city sees the full amount of snow that's in the forecast, this will go down as the all-time snowiest 30-day period on record in Boston. The previous record was 58.8 inches of snow over the 30-day period ending on February 7, 1978. This storm could push that total well over 60 inches, breaking the record.

The snow is taking its toll on area schools. According to Mike Seidel on The Weather Channel, Boston City Schools have already missed six days this year, and will go to school until June 29 as a result. Any additional snow days from this storm could push the city's last day of school into July. Students were originally scheduled to get out for summer on June 19.

Polar Vortex of Doom II

The rumors are true: we will see a major and potentially historic cold snap next weekend, and the polar vortex will have a hand (a trough, really) in the matter.

The polar vortex is a persistent upper-level cyclone that swirls around in the far northern latitudes, keeping bitterly cold air locked in place up around the Arctic Circle. Every once and a while, this circulation will break down and become wavy, with troughs or even individual upper-level lows breaking off from the main circulation in the polar vortex. When one of these troughs or upper-level lows swings down close to or over the United States, it can drag very cold Arctic air with it, causing these major cold snaps.

For the past couple of days, weather models have consistently shown a strong upper-level trough associated with the polar vortex venturing down into the Northeast, which would bring with it bitterly cold and close to record-breaking temperatures beginning next Friday the 13th (spooky!). High temperatures will struggle to get out of the single digits and teens as far south as Pennsylvania and New Jersey, with lows diving far below zero in many interior locations.

It isn't out of the question that parts of interior New York and Vermont could approach -25°F or colder a few mornings next weekend. Subzero lows are even possible across the I-95 corridor from Boston down towards New York City, though it remains to be seen if the Big Apple will hit or fall below zero. The last time New York City saw a subzero low temperature was in 1994, when Central Park hit -2°F and LaGuardia reached -3°F. Kennedy Airport hasn't recorded a subzero temperature since 1985.

[Images: NWS, WPC, NWS, The Weather Channel, NWS, Tropical Tidbits | The graphics in this post were updated at 9:13 PM EST to reflect the latest forecasts.]

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