1.) The Timeline

While I had previously promoted the idea of an uneventful Wednesday morning commute, the latest data suggests a slightly earlier onset to the wintry precipitation than I had hoped. With first flakes in NJ pre-dawn, and heavier precipitation potentially arriving in the 7-8 a.m. neighborhood, things could be slippery in a hurry by the end of the AM rush. The general mantra to this forecast: The earlier you can get out the door Wednesday morning, the better your chances of missing the messiest weather.

The peak for snow and wintry mix will occur from mid-morning (8 a.m.) through early afternoon (2 p.m.). Roads will feature some combination of snow, slush, ice, and/or water. If the worst-case scenario comes true (significant freezing rain), driving conditions may be extremely hazardous or even impossible for part of the day.

By late afternoon Wednesday, an influx of warmer air will force all wintry weather to become wet weather — yes, just rain. That will help to melt and wash away some of the ice and snow accumulation from earlier in the day. However, some of that rain could be pretty heavy, and the risk will remain for pockets of freezing rain. Road conditions may be poor, although probably better than earlier in the day.

As the storm system exits Wednesday night, temperatures will drop again, which could bring about one last hit of snow at the very end. It will be brief, it will be fairly light, and no additional accumulation is expected (especially since the ground will be thoroughly wet by that point).

I honestly don't know what to advise schools to do on Wednesday. It is totally possible that buses will make their morning run before the wintry precipitation starts and their afternoon run after the transition to rain. A delayed opening would be pointless, because that would put the school start time right in the window of worst potential icing. Same deal for an early dismissal. Maybe you delay until weather conditions become clear, and then upgrade to a closing if necessary? Maybe you close out of an abundance of caution? Maybe you risk it and hope for the best? I highly respect any school administrator who has to make a call based on this complicated forecast!

2.) The Snow

NAM model forecast as of precipitation onset Wednesday morning, showing snow (blue) in North Jersey and some wintry mix (pink) in Central Jersey. (College of DuPage Meteorology)

This is a storm where a few degrees on the thermometer (31° vs. 32° vs. 33°) will make all the difference in what weather conditions you experience at a given time.

With temperatures below freezing at precipitation onset Wednesday morning, we'll likely see a burst of all snow from I-78 to the top of the state. Because the ground is so cold, the snow will begin to accumulate rapidly on untreated surfaces.

Far northern NJ, in and around Sussex County, 3 to 6 inches of snow is expected before an eventual (slow) change to rain late-day Wednesday. A couple of inches may accumulate further south, again along and north of the I-78 corridor, before the eventual transition to wintry mix and rain. I'm maintaining a forecast of "up to an inch" from central NJ down along the I-295 corridor.

3.) The Ice

NAM model forecast for midday Wednesday, showing significant wintry mix and potential icing across the northern half of New Jersey. (College of DuPage Meteorology)

So yes, there will be some snowfall accumulations in North Jersey. But the bigger problem for Wednesday, by far, is the potential for sleet and freezing rain causing significant ice accretion (accumulation).

Let's remember the definition of freezing rain — it is not ice pellets (that's sleet). Freezing rain looks, feels, and tastes like regular liquid rain until it hits a cold surface and freezes on contact. As you can imagine, this can lead to an incredibly slippery sheet of ice developing in a very short time. It doesn't take much freezing rain to cause this dangerous "glaze" to occur.

The biggest threat for a glaze of ice (on the order of a few tenths of an inch) will exist from the "snow zone" around Sussex County down to about northern Mercer and Middlesex counties. South of that point, away from the coast, there could be upwards of a trace of ice — certainly still enough to cause treacherous travel.

I've been saying it all day, and I'll say it again. You have to "keep your head on a swivel" and stay extra vigilant to the constantly changing weather and road conditions on Wednesday. There will be windows of safer travel in the early morning and late afternoon hours, but you may have to be patient.

4.) The Rain

NAM model forecast as of late Wednesday afternoon, showing all rain (green) and possibly freezing rain falling across the Garden State. (College of DuPage Meteorology)

Models continue to show good agreement that almost the entire state of New Jersey will transition to all rain. That will likely happen sometime Wednesday afternoon.

Southern New Jersey (south of I-195) and the Jersey Shore will experience almost exclusively rain from this system. That's pretty much the best-case scenario, avoiding the worst icing potential that will probably occur further north and wes.

5.) The Advisories

Right on schedule, the National Weather Service upgraded the watch to a Winter Storm Warning. Concurrently, a slew of Winter Weather Advisories were posted for northern, central, and southwestern New Jersey.

Latest warnings and advisories from the National Weather Service. Pink=Winter Storm Warning, Purple=Winter Weather Advisory.

Here's a rundown of what's in effect and where. (The reason for so many different products is to reflect the varying impacts and timing of Wednesday's messy weather.)

--Winter Storm Warning for Sussex County, from 4 a.m. to 9 p.m. Wednesday.
--Winter Storm Warning for western Passaic County, from 6 a.m. to 10 p.m. Wednesday.
--Winter Weather Advisory for northwestern Burlington, Camden, Gloucester, inland Monmouth, and Salem counties, from 4 a.m. to 9 a.m. Wednesday.
--Winter Weather Advisory for Mercer and Middlesex counties, from 4 a.m. to 11 a.m. Wednesday.
--Winter Weather Advisory for Hunterdon and Somerset counties, from 4 a.m. to 2 p.m. Wednesday.
--Winter Weather Advisory for Morris and Warren counties, from 4 a.m. to 9 p.m. Wednesday.
--Winter Weather Advisory for eastern Bergen, eastern Essex, Hudson, and eastern Union counties, from 6 a.m. to 3 p.m. Wednesday.
--Winter Weather Advisory for western Bergen, western Essex, eastern Passaic, and western Union counties, from 6 a.m. to 5 p.m. Wednesday.

Confused by all that? Me too. Offering such a long and precise list of advisories to cover the state is a little ridiculous, in my personal opinion.

Bottom line: Wednesday is going to be messy, with some combination of wintry and wet weather throughout the daytime hours. Be smart, be safe, and you can count on our weather, traffic, and news teams to keep you updated.

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