The Bottom Line

Our weekend of inclement weather is about to end with a wintry blast.

Over the last 24 hours, forecast models have trended strongly toward accumulating snow for southern, coastal, and possibly central New Jersey on Monday. Probably a surprise for most, coming off the big holiday week. Plus, our forecast had previously leaned toward snow showers rather than an outright snow headache.

With over a half-foot of accumulation possible to the south and east, a Winter Storm Watch is posted for several NJ counties. Gather round and get ready — it's a "South Jersey special," and New Jersey's first real snowstorm of the season.

The Appetizer: Rain and Wind

To begin the forecast, Sunday will be a continuation of Saturday's gloomy, damp weather. Top rainfall totals so far have been over an inch, mainly in a swath of Mercer, Middlesex, and Monmouth counties that got dumped on Saturday evening. We'll add about a quarter-inch to that tally on Sunday, with the best chance of scattered rain through the first half of the day.

Eventually, a cold front will shove those showers off the coast from Sunday afternoon to evening. (To be clear, all precipitation up to this point will be liquid, non-frozen, plain rain.)

As that colder, drier air mass arrives late Sunday, the wind is going to kick up a bit. Top gusts will probably come Sunday evening, around 30+ mph.

And, of course, temperatures will take a big tumble from Sunday afternoon to Sunday evening. We'll go from highs near 60 degrees at Noon, to below freezing around Midnight. (More specifically, temperatures will fall below freezing around 8 p.m. to the northwest and 4 a.m. along the southern coast.)

Snow Timeline

The most important piece of the puzzle is a piece of energy that will ride along that frontal boundary to our south and east. The center of that storm system will eject from the North Carolina coast around midday Monday.

That geography is important. Because the core of the storm will be so far south, it means: 1.) NJ will be on the cold, snowy side of the system, and 2.) we will miss the heaviest bands of precipitation.

Let's break the storm's progression down by quarters, just to give you an idea of how things will play out, starting late Sunday night:

—Midnight to 4 a.m. Monday... First bands of precipitation arrive along the southern and eastern edges of NJ. Initially, there may be some rain or icy mix there, before transitioning to all snow by daybreak (at the latest).

—4 a.m. to 8 a.m... The brunt of the storm kicks in, as heavier snow bands set up over southern New Jersey. Visibility will drop, and accumulation will begin.

—8 a.m. to Noon... The time of the most widespread precipitation, as snow bands potentially reach north of Interstate 195 and possibly Interstate 78.

—Noon to 4 p.m... The peak of the storm wrapping up. Snow will become more scattered and generally lighter, but may continue to slowly accumulate.

—By 6 p.m... All snow will have exited the coast. Overnight temperatures will be unseasonably cold, in the 20s.

In other words, this is mostly a daytime snow event. Bad news for commuters, especially across the southern half of the state.

Accumulations

Before I talk numbers, I do want to mention the three limiting factors that could have a huge impact on how much snow reaches and "sticks" to the ground:

1.) After a 10-day stretch of above-normal temperatures, the ground is pretty warm. Soil temperatures are averaging 50 degrees across the state — way above freezing. So snowflakes may initially melt on contact, preventing accumulation. But temperatures will be crashing. And heavy snowfall can still overcome the warmest ground. So accumulation will happen — it might just take a while after the flakes begin to fly.

2.) Cold air is dry air. And with dew points descending into the teens on Monday, a lot of our precipitation may evaporate before even reaching the ground. That's especially true in colder, drier NW NJ, where snowfall is expected to be scarce.

3.) The temperature profile at onset (still slightly above freezing along the south coast) may lead to a few hours of rain or icy mix to start. Sleet does not accumulate nearly as quickly as snow. (And rain doesn't accumulate at all, of course.) So we can't quite call this an "all snow" storm.

Now that those important hesitations are out of the way, let's break down each region of the state, as illustrated on my snow map.

The latest snowfall forecast for late Sunday night to Monday, as of Sunday morning. (Dan Zarrow, Townsquare Media)
The latest snowfall forecast for late Sunday night to Monday, as of Sunday morning. (Dan Zarrow, Townsquare Media)
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—Southern Coast ("The Sweet Spot")... Home of the heaviest precipitation bands, and the longest-duration snowfall. I've settled on an estimate of 4 to 8 inches here. Anything 4+ is plowable and shovelable. And I consider 6+ to be a significant, major storm.

—The Rest of South Jersey ("The Unknown Zone")... This would be the area most susceptible to the storm track "wiggle". I'm forecasting 3 to 6 inches of snow accumulation here. A period of moderate to heavy snow is expected — how long it lasts and how far north it gets will dictate which end of that range is more likely.

—The I-295 and I-195 Corridors ("Nuisance Snow")... It's going to take a while for snow bands to reach this part of the state. And even longer for snow to stick. But I think there's still enough evidence pointing toward a "minor" snow event, with 1, 2, or 3 inches on the ground. Remember: That's falling during the daytime hours, so travel conditions could still turn treacherous.

—The Middle of the State ("Don't Expect Much")... Most models show at least some snowflakes creeping toward the Interstate 78 corridor. And if you get a solid snow band for an hour or two, that could whiten up the ground. But anything over an inch would be difficult, given the dry air, warm ground, and current storm track. As the map shows, zero is a definite possibility here.

—North Jersey ("Not Your Storm")... Maybe some light snow, maybe not a single flake. In any case, I expect little to no accumulation near the top of the state from this storm.

For the record, it is really weird for South Jersey to see the first substantial snow of the season before North Jersey. (I don't have statistics handy about whether that's happened before — I'll do some research and get back to you.)

Confidence

No weather forecast is complete without a measure of confidence, how sure we are that a given situation will play out.

In this case, even though "first flakes" are less than 24 hours away, confidence is only low/moderate. That's because of the dramatic shift in model guidance, meaning it's hard to get a good feel for what to believe and what to not. I don't think the storm is just going to "disappear" or "go away" at this point — but the details are shaky.

I think there are three things that could change in the forecast going forward:

1.) Totals in the northern half of the state may be too high. The least snowy model (the Euro) keeps any and all accumulation south of I-195.

2.) Snowfall in southern New Jersey may be too low. If you go by raw model output, double-digit snowfall (10+ inches) is possible. I think the "limiting factors" I listed above will ultimately win out. But it's hard to ignore almost every model pumping out the suggestion of a major winter storm for NJ's southern coast.

3.) We're always watching for "the wiggle" — an inevitable last-minute ~30 mile shift in a storm track that can have dramatic impacts on snow totals and apparent weather conditions. In this case, I'm most concerned that a shift to the north will introduce warmer temperatures in South Jersey. Warmer = less snow = more rain/mix = lower totals = a busted forecast.

To be clear, I have put forth the most realistic and honest forecast as I see it right now. Let's see how the afternoon model suite trends, and then potentially revise these numbers once more time late Sunday afternoon.

Advisories

A Winter Storm Watch has been issued for Atlantic, Cape May, and Cumberland counties, from 3 a.m. Monday morning through 5 p.m. Monday evening.

A Winter Storm Watch (blue) has been issued for the three southernmost counties in NJ, from late Sunday night to Monday. (Townsquare Media / AerisWeather)
A Winter Storm Watch (blue) has been issued for the three southernmost counties in NJ, from late Sunday night to Monday. (Townsquare Media / AerisWeather)
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That is the area of the state most likely to see significant (5+ inch) accumulation. And that is the time frame when travel conditions may get treacherous.

If the forecast holds steady, the watch will be upgraded to a warning Sunday afternoon. Additional advisories will likely be issued farther north, anywhere that 3+ inches of accumulation is possible. When a warning or advisory is posted for your area, that's your cue to make plans and finish preparations for the storm.

Impacts & Action Steps

The first winter storm of the season is often challenging, because we need to dig the shovels, snow brushes, heavy coats, hats, and gloves out of storage. You may also be running low on supplies like salt, batteries, and de-icer wiper fluid.

Sunday is your opportunity to collect those supplies and get ready. Remember, first flakes will not arrive until after late Sunday night (after Midnight).

The biggest impact from this winter weather event will be travel conditions. They're really going to stink during the peak of the storm, especially across the southern half of the state. Reduced visibility, icy roads, slippery sidewalks, and airport delays galore. The vast majority of winter weather related deaths occur from traffic accidents.

School closings are possible. (If not likely, in South Jersey.) I would expect those calls to be made once warnings and advisories come out. Keep in mind, the most widespread steady snow will fall during the school day on Monday. So delayed openings and early dismissals seem unlikely.

Heavy snow and ice accumulation on tree branches and power lines could cause some outages. Although this isn't a blizzard or a dramatic wind storm, so hopefully blackouts will only be sporadic.

Coverage Plan

I will almost certainly put out one more comprehensive weather blog post late Sunday afternoon. Covering the latest timing and accumulation forecast, and reviewing any new warnings and advisories. Look for that by about 5 p.m.

Our on-air coverage will slowly ramp up through Sunday evening and overnight. And then we'll be in full Winter Weather Alert mode starting with NJ First News at 5:30 a.m. Monday. An early morning weather blog update will give you the latest snow timeline for Monday too.

Thanks for reading and making it this far. Be smart, stay safe, and happy winter!

Dan Zarrow is Chief Meteorologist for Townsquare Media New Jersey. Follow him on Facebook or Twitter for the latest forecast and realtime weather updates.

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