Severe winter weather likely this weekend

John Cifelli, Meteorologist | January 18, 2019 | Weather
  • Dangerous winter storm likely for central, northern New Jersey Saturday night into Sunday
  • Snow, sleet, freezing rain, and wind to deliver a high impact event
  • Frozen ground and heavy rain raises flooding threat elsewhere

Winter has been relatively benign for New Jersey since a false start snow event in mid-November. We’ve had plenty of moisture and plenty of cold, but they haven’t much lined up together save a couple light snow events for the southern half of the state over the last two months. That’s slated to change in dramatic fashion this weekend, with a moisture-laden storm set to wallop the state with up to a foot of snow in places, notable ice accrual in others, and flooding rains elsewhere. This time around frozen precipitation will have the largest effect on the northern half of the state, while enough rain is expected in southern New Jersey to raise flooding concerns. After a fair day Saturday, things will quickly deteriorate around sundown.

Our weekend storm will develop over the Central Plains throughout the day on Friday before traversing through the lower Ohio Valley on Saturday. Embedded within the southern branch of the jetstream, it will sop up moisture like a sponge from the Gulf of Mexico as it slides east. Meanwhile, one Arctic high pressure center will be shunted east away from New England into Canada Friday. A fresh Arctic air mass will arrive on its heels, moving through the Great Lakes toward the mid-Atlantic by Saturday. As the low pressure center gradually deepens and moves toward New Jersey, it will slam into a wall of cold air anchored just north of the state, bringing a mixed bag of wintry weather to parts of central and northern New Jersey.

Precipitation will begin late afternoon, as mostly snow, even in southern New Jersey. Here a transition to plain rain occurs quickly, after perhaps a coating or so of accumulation. North of 195, look for a burst of heavy snow from a band that will gradually trudge north as the evening progresses. This band will not only produce the heaviest snowfall rates, it will also demarcate the areas seeing snow from those that contend with sleet and freezing rain to its south. From Mercer and northern Monmouth and all points north, it really won’t matter what exactly is falling from the sky Saturday night — you won’t want to be out in it. Since our surface low is slow to strengthen, I don’t see a lot of warm air working its way north and west as the night progresses at the surface. Aloft it will be a different story, with a marginally thick layer of air above freezing, changing snow to sleet or freezing rain. Central New Jersey — defined here as Mercer, Middlesex, northern Monmouth, Hunterdon and Somerset — are the tricky areas to forecast for at this point. A little more cold air aloft means sleet will be the dominant precipitation type. A little less means that there is freezing rain and a significant icing event on the table. Further north, I think north of Route 80 and the northern boroughs of New York City stay as mostly snow and sleet, with less threat of icing.

After midnight, enough warm air creeps north to change things to plain rain in Central New Jersey, perhaps as far north as Route 78. The damage will have been done with significant snow and ice accumulations. Power outages are likely in areas that see heavy, wet snow followed by ice accrual.

As the storm pulls away Sunday morning, the fresh Arctic air mass lingering just to our north comes crashing down across the state. With a brisk northerly wind, it will be painfully cold. Sub-zero windchill values will be widespread Sunday afternoon and evening. Some parts of the state will approach zero Sunday night — that’s temperature, not wind chill. Monday morning will be just as bad, until winds relax later that day, setting the stage for more bearable cold on Tuesday.

Rainwater tends not to be absorbed into ground that’s frozen solid. The long stretch of overnight lows in the teens and twenties the last 10 days or so means that road flooding and flash flooding potential is there for those who don’t see snow, sleet or freezing rain.