Nasty blast of winter: 7 things to know about ice, cold, & snow
This is your Friday evening forecast update for this weekend's potent winter storm. We're now less than 24 hours away from feeling the impacts of this blast of wintry weather. It's time to start really getting serious about the potential for some heavy snow, significant ice, and pouring rain. Followed by an arctic wind, extreme cold, and a flash freeze.
1.) Part 1: Initial Burst of Snow
Our winter storm is expected to arrive in New Jersey Saturday afternoon (between about 1 p.m. and 5 p.m.) Initial precipitation is likely to be snow for most of the state. For southern and coastal New Jersey, it might be all rain, even at the start. (But that's not a guarantee — given the colder temperatures that associated Friday morning's snow, I think it's worth keeping the door open to a brief period of snow at onset.)
The big concern in this phase is how heavy the initial bands of snow might be — you don't be caught off-guard by rapidly deteriorating travel concerns. It's wholly possible that northern/central NJ has an inch of snow on the ground by about 6-7 p.m.
2.) Part 2: Transition to Mix/Rain
Saturday evening, warmer air is going to surge up from the south. This will force a transition from snow to wintry mix (snow/sleet/freezing rain) to rain, as the freezing line drifts from south to north. By Sunday morning, it looks like almost all of NJ will have seen a transition to rain, with snow/sleet limited to far North Jersey (along and above I-80).
The big concern here, hands down, is significant ice accretion (the technical term for accumulation). If warmer air only invades the atmosphere just above the surface, while the ground remains cold, we could see an extended period of freezing rain. I've seen models spitting out upwards of a half-inch to an inch of total ice — that would be incredibly disruptive and dangerous. Driving and/or walking would become very difficult, and widespread power outages due to downed trees and line would be possible too. Ice storms are nasty business — please do not underestimate the icing potential of this storm.
Another concern is the potential for flooding, given that up to 2 inches of rain will fall in the warm sector of the state (southern 2/3). If storm drains are blocked by snow, ice, and/or leaves, minor street flooding may occur.
3.) Part 3: Final Hit of Snow
As the storm begins to exit New Jersey midday Sunday and precipitation tapers off, temperatures will start to crash. As we once again fall below the freezing mark, one more quick hit of snow is possible. Additional accumulation is expected to be light in this stage. Precipitation should exit the Garden State completely by Sunday mid-afternoon.
The big concern overall is that far North Jersey will remain snowy for the entire duration of the storm, contributing to some big snow totals. While the truly heaviest snow from this storm (up to 2 feet) will fall across Upstate New York and New England, 6+ inches of accumulation is more than enough to make getting around very difficult.
4.) Part 4: Bitter Cold
A brisk northwesterly wind will kick up around midday Sunday, sustained 15 to 25 mph with gusts to 40 mph. That wind will cause temperatures drop sharply through Sunday afternoon. It's going to fall so far, so fast that any residual puddles and wet surfaces could easily ice over Sunday night.
By Monday morning, temperatures will be in the single digits for most of New Jersey. With a continuing bitter breeze, the wind chill will sink as low as -15. That brand of cold is painful and downright dangerous, especially given the likelihood of power outages from the storm.
All or part of the six northernmost counties in New Jersey have been upgraded to a Winter Storm Warning:
--Noon Saturday to 6 p.m. Sunday... western Bergen, western Essex, and Passaic counties
--1 p.m. Saturday to 4 p.m. Sunday... Morris, Sussex, and Warren counties.
A Winter Storm Watch continues for:
--Noon Saturday to 6 p.m. Sunday... eastern Bergen, eastern Essex, Hudson, and Union counties.
--1 p.m. Saturday to 4 p.m. Sunday... Hunterdon and Somerset counties.
The Warning means significant wintry weather is expected to lead to poor, if not downright dangerous, travel conditions. The Watch is a "wait and see" message — depending on which way the forecast leads (colder and snowier/icier, or warmer and wetter), that will become wither a Warning or a less-severe Advisory on Saturday.
I could see additional advisories issued for minor snow/ice across central and southwestern NJ at some point. South Jersey and the Jersey Shore, this ain't your storm.
By the end of the weekend, we may also have advisories and warnings posted statewide for wind and extreme cold too.
6.) Coastal Flooding
Even though this is not a coastal storm, the surf is predicted to rear its ugly head during two high tide cycles — Saturday afternoon and Sunday morning. About a foot of surge could cause minor saltwater inundation issues in vulnerable areas along the Jersey Shore.
Freezing spray could be a problem along the oceanfront too, given how cold it's going to be Sunday night into Monday morning.
7.) Forecast Confidence
No weather forecast is complete without a statement of the forecaster's confidence that it will come true. I think we've got the timeline nailed down pretty well. It's also very clear that the heaviest snow will stay well west and north of the Garden State. Despite the complicated nature of the storm, I also think it's pretty certain that the warm air and snow-mix-rain transition will occur as predicted.
The trouble is in the totals. The numbers. It is incredibly complicated — dare I say impossible — to nail down exactly how much snow, ice, and rain we're going to see area each area of the state. (I wish I didn't have to produce a specific snow map for an event like this — but the people of New Jersey would revolt if I didn't.)
Even the models are having trouble resolving the precipitation type makeup of this storm. The last few runs of the GFS and NAM show a transition from snow to mix even for North Jersey, which would limit snow accumulations to a category less than I'm currently predicting. I've been purposefully leaning toward a colder, snowier solution, and that's where I'm going to stay. Not exactly happy or comfortable, but I think I've produced a reasonable forecast here.
We'll take one more shot at this forecast Saturday morning (I'm aiming to publish by about 9 a.m.) And then, we'll be live on-air and online with updates as conditions roll downhill starting Saturday afternoon.