December arrives with wintry blast

John Cifelli, Meteorologist | November 30, 2019 | Weather
  • Long duration event brings a mixed bag of winter weather
  • Biggest impact will be on northern New Jersey
  • Mostly/all rain for southern New Jersey

Meteorological winter begins Dec. 1 each year, and on cue parts of New Jersey will enter the new season with snow, sleet and freezing rain. A two-part, long-duration winter weather event will affect Central and Northern New Jersey as early as Sunday morning, and impacts will linger into Monday evening.

Through Saturday evening, the weather will not make for any travel impacts. Aloft, a strong mid-level low pressure center will traverse the Ohio Valley towards the mid-Atlantic. The first wave of precipitation comes Sunday, and is associated with warm aid aloft moving across the state in advance of the mid-level low’s approach. This first wave of a wintry mix will taper off Sunday night. Once this wave of precipitation moves through, a surface low will spawn Sunday afternoon over or just east of the Delmarva Peninsula. At this point the steering features aloft are crawling quite slowly, which will keep the surface low pinned near the coast. As a result, precipitation will build back across the state Monday. We will be on the colder side of the surface circulation at this point, and what falls will do so as snow. Surface and upper-level lows will finally move east and end their impact on New Jersey Monday night.

Shortly after daybreak Sunday, light rain will begin in Southern New Jersey. Through mid-morning, light precipitation will spread north, beginning as sleet and snow along and north of the Route 1 corridor. I think precipitation flips to freezing rain and plain rain by midday in Mercer and Middlesex Counties, with more frozen and less liquid precipitation as you go north. I think the bulk of weather related travel impacts will be north and west of the Route 202 corridor during the day on Sunday.

Sunday evening and night the first wave of precipitation tapers or even ends for a stretch. That will be a common theme for this system — precipitation will come in fits and starts, at varying intensities. Although the total duration will be 36 to 48 hours, there will be stretches when nothing is falling outside, regardless of precipitation type. Monday morning the surface low will be strengthening, and the moist atmosphere from Sunday’s precipitation will be ready to be wrung out again. Back-end snows are notoriously difficult to predict and often don’t come to fruition. Confidence is higher this go around because of the upper-level features which will keep everything from progressing east as usually occurs with winter storms. However, snow on Monday will be banded in nature. It’s one of those setups that will drop a few extra inches in some places, and skunk others nearby with little or nothing.

The expected path of the surface low favors Northern New Jersey for winter weather, and temperatures at the surface and aloft on Monday might result in rain if anything falls in Southern New Jersey. It’s very clear that both Sunday and Monday’s rounds of winter weather will be largely confined to the north. Giving out a “total snowfall” accumulation isn’t really helpful here, because of the two-part nature of the storm. Look for 2 to 4 inches north of Route 80 Sunday, and 1 to 2 inches or so of sleet and snow along the Routes 78 and 202 corridors. Far northern and elevated sections of Sussex, Warren, and Passaic Counties will see more, up to 6 inches by Sunday night.

Monday’s back end snows could bring another 2 to 4 inches to anyone in the northern half of the state, but we will have to get a little closer to that timeframe before knowing if those snows will actually come to fruition. I’ll say this — if the surface low deepens quick enough, the Northern New Jersey suburbs of New York metro could overperform and be in the bulls-eye. I’ll have a better idea of that potential in an update Sunday midday.