A wintry start to the week: Snow and sleet Monday and Tuesday

John Cifelli, Meteorologist | February 10, 2019 | Weather
  • A two-part system will bring frozen precipitation to New Jersey Monday and Tuesday

  • The first bout focuses on southern New Jersey

  • The second round affects northern locations

A robust winter storm will slowly move from the Great Plains through the Great Lakes over the next three days. Coupled with strong Arctic high pressure in place over southeast Canada, New Jersey will see two rounds of wintry precipitation beginning after dark Sunday. All of the next four commutes will pose varying amounts of difficult travel before the system clears the area late Tuesday night and Wednesday morning.

As Sunday evening approaches, clouds will build in from the west and light precipitation will begin after dark. This first round of light snow and rain is less the result of a true surface low pressure center, and more a result of warming temperatures aloft well in advance of the main event to come Monday night. Except for Cape May County, much of southern and central New Jersey will see light snow overnight, with 1 to 3 inches likely south of 195. North of 195, look for a coating to an inch, and it’s over well before daybreak. Snow showers will linger into the morning commute the further south you go. In fact, extreme southern New Jersey and Cape May may not see precipitation end at all as the second wave of energy arrives late in the day Monday.

Snow will creep north slowly Monday night. A 1040 mb high pressure centered in southeast Canada will funnel cold, dry air at the surface across New England and into the northern mid-Atlantic, which might hold off the onset of precipitation until daybreak for far northern New Jersey and suburbs of New York City. Elsewhere, steady snow will fly for the morning commute. Precipitation will quickly change to sleet and then plain rain in southern New Jersey, where another inch or so will accumulate Monday night before the switch to plain rain. As the afternoon progresses, the snow/mix line will trudge northward. Low level cold will hang tough with the primary low so far away, still centered in the Great Lakes at the height of the storm. It’s strength, positions, and orientation is not ideal for scouring out sub-freezing temperatures at and near the surface. On the other hand, the surface high in southeast Canada is very strong and in a good position to reinforce colder, drier air. As a result I think an extended period of sleet and freezing rain is likely in the afternoon and early evening for the northern half of the state after a couple inches of snow has already fallen.

Eventually, the surface low slides into New England, dislodging the Canadian high, and bringing the whole state above freezing Tuesday night. Precipitation will end as drizzle, falling on several inches of snow, sleet and freezing rain. A note about the freezing rain — I think this has the potential to be a significant ice accrual in Sussex, Warren, Passaic, Morris and western Bergen County Tuesday night. Precipitation will be light, low level cold will be shallow, and upper level temperatures will be warm enough to melt snowflakes on their way down to the surface. The saving grace with this system is that the winds will be light, which reduces the risk of power outages. Also, even northwestern New Jersey should be above freezing at the surface by daybreak.

There’s plenty of pitfalls with this forecast. Model guidance is all over the place with when and where the transfer of energy between the primary surface low and the developing coastal low is to occur. There’s no chance here for an all-snow or even an all-frozen precipitation event for much of New Jersey. What we do have is a fragile balance between the primary low, the surface low and the Canadian high. This is the time of year when the Atlantic is close to at its coldest. The difference between a southeast wind and a northeast wind is a couple degrees of surface temperature, and a couple more or less hours of frozen precipitation. The more northerly component to the surface wind in your neighborhood, the more frozen precipitation you will see. The upper levels are going to warm above freezing, so as I said, a major snow event is off the table. The difference between 31 degrees Fahrenheit and 33 degrees Fahrenheit at the surface to a few thousand feet above will be hours of sleet and freezing rain versus plain rain. The right word is indeed “fragile.”

As it stands right now, I think part two of this 1-2 wintry punch will deliver 3 to 5 inches of snow and sleet with up to .3 inches of ice accrual for northwest New Jersey as defined previously. A bit further south and east, including the 202, 1, and 95 corridors, look for 1 to 3 inches of snow and sleet with up to .1 inches ice accrual. Further south and east, expect an inch or so of snow and sleet with no icing. This forecast is likely to change in terms of precipitation type but not impact. Expect a moderate to high impact weather event Monday night through Tuesday for central and northern New Jersey, regardless of what exactly ends up accumulating, be it snow, sleet or freezing rain. Updates will be forthcoming.