Nor’easter update: 48 hours of wintry weather will peak on Monday
Not much has changed amongst the forecast models lately. That's a good thing in weather forecasting, as it adds to our confidence that we have a decent handle on the storm. We will, of course, continue tweaking and tightening our expectations until the storm arrives. (And yes, that includes calling double-digit snowfall likely for a substantial chunk of the state.)
The biggest piece of news is that the National Weather Service rejiggered their warnings, watches and advisories, now that we're within 24 hours of first flakes. Here's the breakdown:
—Winter Storm Warning from 5 p.m. Sunday to 1 p.m. Tuesday (44 hours!) for Hunderdon, Mercer, Middlesex, Morris, Somerset, and Warren counties.
—Winter Storm Warning from 10 a.m. Sunday to 10 a.m. Tuesday (48 hours!) for Camden, Gloucester, and Salem counties.
—Winter Storm Warning from 1 p.m. Sunday to 10 a.m. Tuesday (45 hours!) for Burlington, Monmouth, and inland Ocean counties.
—Winter Storm Watch from 5 p.m. Sunday to 1 p.m. Tuesday for Sussex county.
—Winter Storm Watch from Midnight Monday to 6 a.m. Tuesday for Bergen, Essex, Hudson, Passaic, and Union counties.
—Winter Weather Advisory from 10 a.m. Sunday to 10 a.m. Tuesday for Atlantic, inland Cape May, Cumberland, and coastal Ocean counties.
Warnings mean it's time to get serious. No matter where in New Jersey you are, you're likely to see at least some snow. For much of the state, you'll see a lot of snow. Travel will very difficult for a period of 24 to 48+ hours.
For this evening's snow map, I decided to do something a little different. Because this is such a complicated, high-impact, and long-duration winter storm, I decided to show how much snow will be on the ground Monday morning, at the start of the Monday evening rush hour, and then the grand total as the storm departs on Tuesday. (Note: These are cumulative totals — in other words, how much snow I expect to be on the ground at each time marker.) Hopefully that extra information makes planning your Sunday, Monday, and Tuesday easier.
For the rest of this post, I want to concentrate even more on the timing of the storm's impacts on New Jersey. Let's break up the storm's 48-hour evolution into 4 phases.
Phase 1: A Slow Start (Sunday)
After several days of unseasonable cold, our atmosphere is very dry. So as our storm system initially approaches from the west, it will take a while for the air to moisten up enough to allow snowflakes to make it to the ground.
For the southern half of the state, I expect first flakes between about 1 p.m. and 4 p.m. Sunday. They will spread from southwest to northeast, eventually reaching the top of the state by about 9 p.m. (give or take). This initial precipitation will be all snow and fairly light. Slow accumulations are possible, especially since the cold ground will allow snowflakes to stick immediately.
Phase 2: Ramping Up, Warming Up (Sunday Night)
Overnight, the inland low over the Ohio Valley will start to fade, transferring its energy to a new coastal low forming off the coast. As it does, we anticipate a warming trend in the lowest mile of the atmosphere. That will have little consequence for the northern half of the state, as scattered light to moderate snow will continue to fall and slowly accumulate. But for southern New Jersey, a flip from all snow to sleet and/or plain rain seems likely. (How far north the rain-snow line gets overnight is one of the big "bust points" of this forecast, by the way.)
Phase 3: The Brunt (Monday)
After sunrise on Monday, our coastal storm will make its closest pass to New Jersey. That means we face the heaviest precipitation and strongest winds. As long as the storm track holds close to what I'm thinking, much of the area that flipped to mix/rain overnight will transition back to snow by about midday Monday. Heavy snow bands, with snowfall rates potentially in excess of an inch per hour, will really make travel conditions sloppy. (How widespread and heavy the mesoscale bands get is the other big "bust point" of this forecast.) Again, peak storm intensity will be from Monday morning through Monday early evening.
The nasty wintry weather will be made worst by the fierce northeast winds, gusting up to 50 mph. That will cause blowing and drifting snow — near-blizzard conditions are possible, as visibility is severely reduced. Those wind gusts, especially when combined with the weight of snow and ice, could also bring down trees and power lines. Power outages during a powerful winter storm are not good.
Finally, we face a pretty serious threat of coastal flooding, as all that wind will drive ocean water toward the Jersey Shore. Tidal models have been very consistent in showing about 3 feet of storm surge along all east and northeast facing coastlines. That's easily enough to cause moderate category flooding for three or four high tide cycles in a row, Monday and Tuesday. I'm especially concerned about flooding in the back bays and tributaries, as they will not have an opportunity to drain much at low tide. Some spots may exceed major flood stage.
Phase 4: Tapering (Tuesday)
Additional accumulating snow is likely for all but far southern and coastal New Jersey Monday night through Tuesday morning. (Even the rainy southern coast could see a burst of snow at the tail-end of the storm, as winds become northerly and temperatures crash.) Eventually, things will start to wind down after daybreak Tuesday. I think snow will substantially end by around midday on Tuesday, but wouldn't rule out scattered snow showers and flurries into the afternoon.
The Bottom Line
Our recent blast of cold air will NOT go to waste this time around. This nasty nor'easter will drive heavy snow, sleet, rain, wind, and surge through the Garden State for an extended period of time. As long as you don't try to drive anywhere, you'll probably be just fine.
Now that warnings are issued, I expect many school districts will opt to announce closings for Monday and possibly Tuesday, given the expected severity of the storm.
I'll take at least one more stab at a snowfall map early Sunday morning, to be posted around the 9 a.m. hour. And then we'll move into "nowcasting" mode to guide New Jersey through what will likely be our most widespread and substantial snowstorm in quite some time.
Until then, have a wonderful night!