Forecast update on overnight snow, wintry mix, and rain
Light snow fell steadily in North Jersey Sunday, but a potentially treacherous transition to sleet, freezing rain, and then rain is expected by Monday morning.
This winter storm forecast boils down to what happens at about 4 a.m. Monday morning. Period. That's when an influx of warmer air is expected to bump temperatures above freezing throughout New Jersey. (Yes, temperatures will rise significantly overnight, particularly in North Jersey.) That is also when the heaviest precipitation of this storm system will start to arrive.
Therefore, the faster and earlier the transition from snow to rain, the better it will be for the Monday morning commute. Any deviation from this timing - warmup, then heavier stuff - could result in a quick pileup of snow and/or ice, especially along and north of Interstate 80. (And possibly as far south as Interstate 78). As I'm sure you're aware, there's a big difference between a wintry commute and a wet one.
As of this writing (8 p.m. Sunday), we are entering a relative lull in snowfall, after a healthy coating to 1+ inch of snow fell and accumulated across North Jersey earlier Sunday. A slot of dry air will keep snow to a minimum through early Monday morning, before precipitation increases again by daybreak.
As the aforementioned overnight warmup changes the temperature profile of the atmosphere, any snow will (hopefully briefly) change to sleet and/or freezing rain for a time, before going all rain. A prolonged period of freezing rain would be a worst case scenario here, as just a little bit of ice can lead to major headaches. A next-worst case scenario would be colder air allowing up to 5 inches of snow to accumulate in around far North Jersey - for many, that would be the first "plowable" snow of the season.
A Winter Weather Advisory continues for Sussex, Warren, Morris, Western Passaic, Hunterdon, Somerset, Middlesex, and Mercer counties through Monday morning.
My biggest meteorological concern at this point? Temperatures have been holding 3 to 5 degrees below forecast so far in spots. That would lend toward a slightly later transition time, and hence a more wintry solution. Having said that, I have no real reason to change our thinking - this has been a remarkably consistent forecast for days now.
At this point, there's nothing more for a meteorologist to do but sit back and watch what falls from the sky. Keep your fingers crossed that Mother Nature keeps on schedule, and enacts the warmup by the time the heavy stuff arrives. 4 a.m. Monday morning.
As always, New Jersey's First News will be live on-air at 5 a.m. with the latest weather and traffic updates to start your day.