It is the 18th day of January. The 29th day of astronomical winter. The 49th day of climatological winter. And we finally have some snow and bitter cold to talk about. The northern half of New Jersey will probably need to dig out the snow shovel, for the first time in a while. And everyone faces a brief period of potential travel headaches as our first winter storm of 2020 gets going.

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1.) Timeline

—Saturday Morning... Quiet and cold to start. Temperatures in the 20s, with light winds. There will be some snow showers in the area, but our atmosphere will probably be too dry for substantial snowfall at ground-level.

—Saturday Midday... First flakes arrive from the west around 10 a.m. Steadier snow moves in early afternoon. That snow should stick to the ground quickly.

—Saturday Mid Afternoon to Early Evening... Peak of the storm. Bands of moderate to heavy snow possible in the "snow zone" to the north and west. Meanwhile, transition from snow to sleet to rain begins south and coast.

—Saturday Evening... Temperatures continue to warm above the freezing mark, forcing an eventual transition from wintry to wet. (Note: most precipitation may end in North Jersey before the flip.)

—Saturday Late Evening... Precipitation largely tapers off by around 10 p.m., with residual showers possible overnight.

2.) Snow Totals

I thought long and hard about how I might change my snow forecast to better capture and communicate snow totals. I thought about bumping my max snowfall to 5". I thought about getting fancy with 0-Coating and Coating-1" contours in South Jersey. But in the end, I have to ground myself in reality — this is a fast-moving, compact, moisture-starved clipper system. I am more concerned about underperformance than overperformance (more on that in a moment). So I opted to keep my snow map exactly the same as Friday.

Saturday's snowfall forecast, as of Friday morning.

—North Jersey (The Snow Zone)... 2 to 4 inches... The combination of the coldest temperatures in the state and the proximity to this storm system's center track makes the northern half of NJ (give or take) the bullseye. This goes slightly beyond "conversational snow" or "nuisance snow" — this is shovelable snow, and certainly enough to snarl traffic for a few hours.

—Central/Southwest Jersey (The Middle Zone)... 1 to 2 inches... Somewhere in New Jersey, there will be a cutoff between "oooooh, pretty snow" and "ugh, just a bunch of rain". I suspect that line will be in this area.

—Coastal/Southern Jersey (The Wet Zone)... 0 to 1 inch... It's all about temperatures and dew points here. It might be cold enough for some wet, slushy snowflakes to start. But a quick transition to rain will put a quick end to potential accumulations. Still, there could be a healthy coating here on grassy surfaces. And it doesn't take much slushy weather to cause travel difficulties, especially on untreated roadways.

3.) Impacts

There will be a brief period from Saturday afternoon through evening where travel headaches are inevitable. Low visibility and limited traction are, of course, the big concerns. Fortunately for those who do have to drive through the snow, it is Saturday. Not a school day and not a big work day (for most). That will limit the number of drivers (read: potential nut jobs) on the road when the snow hits the fan.

Plus, our Winter Weather Alert team gets a break since tomorrow's not a school day either. (Don't worry — they're still on the job for any businesses, churches, and organizations that have to delay or cancel openings!)

Winds won't whip around too badly, so dangerous wind chills and damage are off the table. Those winds will not be from an on-shore direction, so coastal flooding is not expected. Lack of heavy rain means inland flooding will not be an issue. Any period of sleet and/or freezing rain will be brief, so widespread heavy icing is unlikely (although not entirely impossible). Not bad.

4.) Advisories

A Winter Weather Advisory has been issued for 12 counties in northern and central New Jersey. (It has been expanded southward one tier of counties since Friday.)

A Winter Weather Advisory has been issued for 12 northern New Jersey counties, from 10 a.m. Saturday to 1 a.m. Sunday.

The WWA runs from 10 a.m. Saturday through 1 a.m. Sunday for Bergen, Essex, Hudson, Hunterdon, Mercer, Middlesex, Morris, Passaic, Somerset, Sussex, Union, and Warren counties.

An advisory is simply a formal heads-up that accumulating snow and hazardous travel are on the way. It is not as severe as a warning — again, this is not a major winter storm.

5.) Confidence

There are still some differences among our forecast models about how the warming temperatures will ultimately impact snow totals. (For the record, I largely sided with the rock-solid consistency of the Euro this time around, with some help from the NAM.)

Even with a few hours to go before snowflakes begin to fall, I have to contemplate what could go wrong with this forecast. That way, we can all be prepared to adjust our expectations of the ongoing weather and conditions as the storm goes on. Remember: There is no such thing as a "perfect" winter storm forecast.

How might this storm overperform? (In other words, how could more snow fall than predicted?) Models have waffled a bit with the maximum snowfall in the state, at times suggesting 5 or even 6 inch totals are a possibility. And yes, if the storm track wiggles south or pumps out some inch-an-hour snow bands, there is an outside chance of half-a-foot of snowfall in North Jersey. Additionally, if temperatures stay colder-than-expected (i.e. the warmup never happens), everyone in the state would be prone to seeing an inch or so more snow than forecast.

How might snowfall underperform? (In other words, how could this snow forecast possibly bust?) Warmer-than-expected temperatures would obviously make for a rainy rather than snowy situation. If that warming happens primarily above the surface, an extended period of sleet could impact snow accumulations too. I'm also concerned about the dryness of the air. If dew points are too low at onset, or if we get an ill-timed slot of dry air in the middle of the storm, snowfall could come up short (and even be downright unimpressive).

6.) The Rest of the Forecast

Showers should be all wrapped up by the time you wake up Sunday. On paper, increasing sunshine and a high temperature around 40 degrees should help begin the snow melt. However, that high temp will happen early Sunday morning, as a brisk west-northwest wind brings back cold, dry air. By Sunday afternoon, temperatures will dip below freezing again with a wind chill potentially in the teens. A refreeze is possible Sunday night, so watch out for black ice spots.

And then the forecast just looks COLD next week. High temperatures will be stuck in the lower 30s at best for Monday, Tuesday, and Wednesday (at least). The next storm system we have to watch is currently scheduled for next weekend — and an influx of warmer air there could very well lead to wet weather, not wintry.

Please be smart and stay safe out there Saturday. (Unless something crazy happens, this will be my final weather blog for this storm and I will slide back into paternity leave for next week. Have a great weekend, and see you soon!)

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