Wild weather swings ahead for NJ: From warmer to wet to icy
UPDATE as of 4 p.m. Wednesday...
ORIGINAL POST from 6:13 a.m. Wednesday...
The Bottom Line
After weeks of constant cold, we'll be treated to a brief break from arctic air. However, a slow-moving cold front will drive in about 48 hours of active weather. First we get soaked. Then potentially iced over.
I've decided to break the progression of that complicated storm system into five pieces, or phases. Some will be more perilous than others, due to the risks of heavy rain and ponding, wintry mix and icing, and also a flash freeze.
Wednesday: Warming Up
Happy Weather-Rodent Day. No matter what the groundhog has to say, it's going to be a February-ish day across New Jersey.
We're starting off mainly in the 20s. There are some pockets of light fog — that may be freezing fog, so watch for slippery spots.
Wednesday afternoon, high temperatures should reach the mid 40s. Our warmest day in a week or two, depending where in the state you are. And a few degrees above normal for early February. Clouds are rolling in, making for a mostly cloudy day overall. Even so, the warmup will be noticeable.
The daytime hours look dry, but showers may come into play as early as 6 p.m. Wednesday evening.
Phase #1: Initial Showers
As the aforementioned cold front approaches from the west, showers may creep in Wednesday evening through early Thursday morning. With overnight low temperatures mainly staying above-freezing, in the mid 30s, these initial showers would likely fall as light rain.
However, raindrops falling on snow cover can create an icy, crunch, slushy situation. So there may be some initial slippery spots as things get started. Something to keep in mind through Thursday morning.
Phase #2: Plain Rain
As pieces of energy ride through our atmosphere, Thursday will turn into a pretty wet day across New Jersey. Periods of rain are likely for all but the immediate coast, which will fall out of the "highway" of these impulses.
With mild high temperatures ranging from mid 40s (north) to mid 50s (south), anything that falls from the sky on Thursday will be plain ol' liquid rain.
There is one concern here. Rain is nature's most effective snow-melter. So there are going to be some big puddles around. And if storm drains are still blocked by snow/ice, ponding could cause localized issues on roadways.
Phase #3: Heavy Rain
As the main forcing of that frontal boundary approaches, it looks like everyone in New Jersey will get soaked Thursday night. By the time the sun rises early Friday morning, we'll probably one to two inches of fresh rain in the bucket.
Just as in phase 2, there will be substantial snow melt here. Combined with blocked drainage, there could be some ponding and flooding problems.
Phase #4: The Big Cooldown
This is where things will get tricky.
While Friday will start with temperatures mainly near 50 degrees, colder air will cause temperatures to plummet. Within hours, thermometers will fall to about 30 degrees. A dramatic change, which will obviously have an effect on our continuing precipitation chances.
The big transition looks to happen in North Jersey first, just after sunrise. The freezing line will then shift south into Central Jersey by around midday Friday. And then South Jersey should make the switch in the afternoon.
We're really not talking about snow here. Yes, colder North Jersey could end up with an inch or two of fresh snow by the time this thing wraps up Friday evening. But ice is the far greater concern across the Garden State — especially since even light icing can have severe effects on road conditions.
Not to get too technical, but it looks like freezing cold air will invade ground-level first. Meanwhile, about a mile and a half above the surface, temperatures will hold close to 50 degrees for a while longer. (We call this a "warm nose" because of how it appears on an atmospheric sounding.)
That means precipitation will begin as snow high up in the clouds, and then melt in the warm layer overhead. That will force an initial transition from plain rain to freezing rain — that's when raindrops fall and freeze on contact with a cold surface. Talk about slippery. (Especially since crews will not be able to pre-salt and pre-brine roads, due to the preceding heavy rain.)
As the "warm nose" shrinks, sleet will develop. That's from snowflakes melting and then refreezing into ice pellets in the lowest layer of the atmosphere. Again, a potentially slippery situation.
This wintry mix evolution will likely finish with a period of straight snow, as the entire atmosphere falls below freezing. Little to no snow accumulation is expected outside of far northern New Jersey, as I mentioned earlier.
Models are spitting out some incredible ice totals for northern New Jersey, on the order of an inch — enough to cause massive travel disruptions and widespread power outages. I'm not sure I'm buying into the full-fledged "ice storm" description. But conditions could become treacherous suddenly during the daytime hours on Friday.
For most of the state on Friday — south of about Interstate 78 — light icing is a possibility. We'll definitely be on the lookout for slippery spots. Again, it won't take much. And the daytime timing of this big transition will be especially challenging.
Phase #5: Flash Freeze
Any and all precipitation will wrap up across New Jersey by Friday evening, at the latest.
And then temperatures will continue dropping, into the teens by Saturday morning. Such a prolonged hard freeze presents one more problem: A flash freeze.
After an inch or two of rain and significant snow melt, there will be abundant puddles on the ground. I have no doubt they will freeze solid overnight, before having an opportunity to evaporate. Therefore, be mindful that icing could be an issue into Saturday morning too.
We return to the freezer for the first weekend of February.
Saturday will be mostly sunny. But with high temperatures only in the upper 20s, we'll be stuck below freezing all day. (So those frozen puddles won't be going anywhere.)
Sunday looks better. Partly sunny and mid 30s.
We had been watching a clipper system for the Sunday night to Monday time frame. Both the GFS and Euro show that system now taking a more southern track, keeping it away from New Jersey. We're not 100% out of the woods, so it's still worth watching. But let's call it a "miss" for now.
Long-range models show quiet, cold weather through the second week of February.