Your East Coast Winter Storm Run-Up Survival Guide

As a forecaster and communicator, I try and approach my audience a lot like I would my mother. Would my mom understand what I’m talking about? Sometimes I deviate and get nerdy; we all do. But when it comes to the forecast details, it has to be simple, clear, and easy to understand.

So my mother sent me an interesting text message today. She said:

Ok. I’m getting anxious. Or curious. I’ve heard so many maybe this or maybe that’s. I want the truth. I’m sick of speculation.

That’s such a great mom text.

In the run up to this major East Coast winter storm, blizzard, Winter Storm Jonas, whatever you use to describe it, you’re going to get a ton of this speculation.

So today, you’re all my mother, and consider this my survival guide for you.

What’s going on here?

The weather models have been hooked on this idea of a major winter storm in the Eastern US for awhile now. There is good agreement among all the various models we use that something is going to happen. Someone’s getting a major storm.

So how much snow am I getting?

No one can answer that question today unfortunately. What we know is that a number of factors are going to contribute to this storm being loaded with moisture. In other words, someone is going to get a *lot* of snow. It’s just not possible to say who that is yet.

Right, right, I get that, but give me your best shot.

This storm is big, slow, and it has a number of complex parts to it that will make it difficult to peg down until we are closer in than usual. But, some trends have evolved in the last couple days that lead us to believe a few facts about this storm.

First, it will be a *big* storm. That means even if you don’t get snow, you may get impacts. It will be slow moving. It will have wind…lots of wind. It will have major, major coastal impacts. Depending on track, we could be looking at a top 5-10 coastal flooding event for folks from the Jersey Shore into Virginia perhaps. That is a serious issue.

But what about snow? The storm has slowly trended south on the weather models. Additionally, it has a very, very sharp gradient on the north side. In plain English? If you live on the northern fringe of this storm, there’s going to be a razor thin margin between major snow and conversational snow.

Here now, a map of where I think things stand as of Tuesday afternoon. Remember, this is subject to change.

011916_snowrisk
My Own Tuesday Evening Snow Synopsis for the Weekend

The trouble is in New England, New York City, and Northern NJ. The models show a tremendous cutoff in snowfall here. The next map is a weather model’s output for precipitation (liquid, not snow). I’ve focused on the NYC area.

011916_precip
18z GFS Model Precip for New York City area (Weather Bell)

Why am I showing this? Notice how in the Central Jersey area, the model spits out about 1.5″ liquid. Go 50 miles north from there. So, like Orange County, NY? About 0.5″ liquid. A 1″ liquid is roughly equivalent to about 10″ of snow. So 10″ snow difference over 50 miles, and the reality is likely that it will be even sharper than this. You’re talking about (surprise!) a major difference in snow totals likely over a short distance over a major population center.

Bottom line in all this: I have higher confidence in heavy snow hitting Virginia and probably DC right now than I do for the Northern half of NJ, New York, or New England. I don’t focus on North Carolina much since the majority of my family and friends are between DC and Boston. But this has potential to be a big storm in a good chunk of NC also.

Alright, so when does all this unfold?

Snow should start in Virginia as early as later Friday morning, and it probably won’t end until about Saturday night. In Philly, it’s a Friday afternoon start and late Saturday night finish. Add a couple hours to all this as you go north to NYC. I have lower confidence in anything further north, so I won’t speculate beyond this.

What about this coastal flooding?

Yeah, this one goes unchecked sometimes. Snow is way sexier, but this is way more damaging potentially. The NWS office in Mount Holly has done an excellent job highlighting this risk. If you look at storm surge guidance for Cape May, NJ, you’ll see the first high tide cycle impacted late Friday ends up at a water level of about 8.5-8.7 feet. Sandy saw a tide level of 8.9 feet there, October 29, 2011 was 8.7 feet, the December 1992 nor’easter was 8.6 feet. An 8.5 foot tide level would rank in the top 8 all time at Cape May. This one’s big. It’s like a 90’s throwback nor’easter.

011916_Cape May
Cape May Surge Guidance shows a tidal level over 8.5′ Friday night/Saturday AM. This would be a top 10 event without much trouble. (NOAA)

If you live along the coast or Back Bays of New Jersey, Delmarva, Virginia, you should begin planning for the possibility of 2-3 high tide cycles like this. If the storm track shifts a bit or the intensity changes, we could see these values change. It’s a fluid forecast, but it’s a serious issue along the coast. Follow your local NWS office for info and guidance.

So will it be a blizzard?

Maybe for someone. It’s entirely possible, but specific criteria must be met regarding wind speed and visibility. It’s too soon to say exactly where and who or how long, but it’s a distinct possibility.

That’s all for now. Feel free to ask any questions and follow me on Twitter at @mattlanza.

Advertisements

Winter Doesn’t Give Up That Easily…

If you’ve lived in the Northeast for any length of time (in years), you know full well that spring almost never comes without a price. Temps in the 60s, 70s, and even 80s over the last week are going to give way to the harsh reality that winter can still rule in March and even April.

Latest plot of recent and forecasted NAO from CPC

To the left you’ll notice a plot of the NAO..the North Atlantic Oscillation. You’ve probably heard of it before, but in layman’s terms, it’s a measure of atmospheric blocking (high pressure) in the vicinity of Greenland. Traditionally in winter, a negative phase of the NAO spells more troughing and thus colder conditions in the Eastern US. You’ll notice from the graph that since the beginning of February, the NAO has been almost locked in a neutral or positive phase. As such, you haven’t seen quite the harsh conditions you all experienced earlier in the winter. But the red lines indicate the forecast, and that, my friends, is what we call a tanking NAO.

Latest Plot of Recent and Forecasted PNA from CPC

Off to the right, you’ll see another, similar chart…this for the PNA, or Pacific-North American Oscillation. This measures blocking near the West Coast. When this is positive, there is traditionally a ridge present out west, which usually can translate to a downstream trough. When you have the NAO in a negative phase and the PNA in a positive phase, that’s a usual rock solid combination to generate warmth out West and cold in the East. It appears, we have these factors ready to lock in for a good 10+ days, with the +PNA holding on a little longer perhaps than the -NAO.

What’s this mean? With them both in concert, it spells strong cold conditions for the Eastern US and a developing warm pattern and end to storminess out West. As the NAO starts to fade, but the PNA stays relatively positive, it means the cold in the East will ease some, but there’s absolutely no sign of a return to the 60s and 70s you’ve seen recently. Expect some 30s, 40s and maybe occasional 50s if you live in the Northeast Corridor through at least next weekend.

How about snow?

A few snow chances exist over the next week or so. I won’t go into many details about the one on Sunday and the one next Wednesday, but suffice to say, the conditions do exist for potential snow.

3/22 12Z GFS Snow Forecast from Earl Barker's Model Site: http://wxcaster.com/regional_snowfall.htm

In the immediate term, we’ve got a situation tomorrow. The map to the left is this morning’s projection of accumulated snowfall from the GFS model. If you live in NYC, you can ignore this for the most part (think the model is a little too aggressive with snow there). This is mainly west of I-287 and north of I-80…but you can clearly see the risk. For Northwest NJ and the Scranton area, despite what this model is showing, I’d be shifting those bands south a bit, and a solid 6-10″ thumping seems likely…very elevation sensitive this time of year, so the higher up you are, the better your odds for snow. The highest amounts seem banded in an area east of I-81, north of I-80, west of I-87, and south of US Route 20. There is some model debate as to how far south the snow will get (one model brings heavy snow as far south as Central NJ). I am going against that model for now due to a poor track record this winter. But you will want to keep an eye on this situation. And if you live in Northwest Jersey/Northeast PA, tomorrow and tomorrow night look very unkind.

Wish I had better news, but enjoy this last gasp of winter if that’s your thing.

Oh, and you can find State of Occlusion on Facebook too!

Facebook Us…Oh, And Snow.

It’s been a disruptive month for State of Occlusion! Transitioning my life offline from the West Coast to the East Coast, so haven’t had time to blog. I’ve discovered Facebook to be an extremely useful tool to communicate short bursts of information and post maps quickly. I will occasionally use this blog to elaborate on various significant events, but in the meantime, for the latest thoughts and information from me, like the Facebook page and tell your friends. We’ve already got 100 fans…let’s go for 200!

Follow State of Occlusion on Facebook for the latest!

In the meantime, while many in the Northeast enjoyed record warmth this Friday, winter is around the corner ready to take its season back. It will be cooler and extremely windy Saturday, followed by a leveling off of temps Sun and Mon. One storm will swing through Monday, potentially dropping heavy snow on Upstate NY, far N PA, into Connecticut and Southern/Central New England. Round two will affect areas south of I-80, somewhere between DC and New York, bringing the potential for very heavy snow on Tuesday as colder, Arctic air pours in. Right now the best odds for this appear to me to be between Baltimore and Allentown, back west across all of PA into Ohio and east into NJ. Potential does exist for 6″ or more with this storm, so this may cause significant travel issues in the Mid-Atlantic on Tuesday. Cold Wednesday followed by another semi-thaw (though not to the extent you saw this week).

I will post updates on Facebook through the holiday weekend.

So About Next Week…

Tonight's 00Z European Model Forecast for Next Wednesday Evening (http://www.meteo.psu.edu/~gadomski)

I’m not one to go bonkers when it comes to any particular storm (in fact, you read me discussing how I would be apt to NOT hype next week a couple days ago). But I think now it’s obvious we have something rather significant showing up here. The three major models tonight all went nuts for the middle of next week, showing an absolutely massive storm slowly rolling up the East Coast. When all three models lock in on a massive storm, that very often means that they’re right. Models struggle and they can be a bit inconsistent at times, but when it comes to the extremely large, widespread or historic sized events, they are usually quick to hit on things. I’m not saying that next week’s storm will be historic, but there’s no question we’re now looking at a significant to major event for much of the Mid-Atlantic and Northeast.

Tonight's 00Z GFS Model Forecast for Next Wednesday Evening (http://www.meteo.psu.edu/~gadomski)

So what are the details? Well, it’s far too early to speculate, but we’ll do just that because we can. Based on tonight’s model runs, we’d be looking at a snow to mix/rain ending as snow event from I-95 to the coast (and even a little further inland from there), with extremely heavy snow/mix possible from the Smokeys north into Upstate NY and interior New England. The storm is also extremely slow moving. For example, the precip begins in Philly on tonight’s Euro run at about Midnight Wednesday and does not end until about 9-11 AM Thursday. Snow moves into the Albany area around 9 AM Wednesday and doesn’t depart until after Noon on Thursday. These aren’t forecasts…they’re just examples of what the model is showing and emphasis on a 24+ hour event.

Tonight's 00Z Canadian Model Forecast for Next Wednesday Evening (http://www.meteo.psu.edu/~gadomski)

The other issue then is track. Tonight’s runs are up along or just inland from the coast. That is extremely unfavorable for heavy snow from DC-Boston…that’s a wet track, not a white one. However, if you look closely at each model’s ensemble mean, you’ll see the track is still fairly far offshore. What does this mean? That the operational models *may* be on the extreme west edge of the track forecast envelope. I wouldn’t go shouting from the rooftops just yet, but it’s something to keep in mind.

We’ve seen a lot of storms the last couple winters, but this one I think is the most impressive looking in terms of physical size and slow track. We’re in a powder keg pattern right now, and this may be the fuse that helps things explode. I’m not going to get into details of the meteorology behind what’s happening right now, but we need to watch things very closely over the next few days. But each model run has looked more impressive with this storm, not less impressive, and that trend may continue as we get closer.

Unfortunately, I’m heading out of town Friday afternoon…well, actually I’m moving, but taking a week or so to drive to Texas, so my updates will be much more infrequent. However, make sure you “like” State of Occlusion on Facebook, as I’ll post updates each night/morning with the latest information. This really could be a big time event, so stay tuned!

What 2 Watch 4

Watching the Onion Sports Dome tonight, so there’s a play on SportsCenter. A couple things to watch. As the annoying snow/ice/sleet/rain storm exits the Northeast tonight, attention focuses on the next two systems. The first one looks to bring a quick hitting shot of snow in a couple days, followed by a much stronger and larger system next week, who’s ultimate fate remains to be seen.

GFS Forecast for Friday Morning, credit: PSU E-Wall (http://www.meteo.psu.edu/~gadomski)

A very quick moving system will swing through the Mid-Atlantic and Northeast Thursday night and exiting Friday afternoon. The map to the left shows the GFS forecast for Friday morning, which has a pocket of moderate to heavy precip in Central Jersey and just south of Long Island. This is a pretty cut and dry situation, with the system sliding through. The only final question is on track. Once that’s in line, we can pin down amounts and locations. Right now it appears that there will be a solid stripe of 2-4″, surrounded by lighter amounts. At this point, the models pin it north of the Mason-Dixon Line and northwest of I-95. So Philly-NYC expect roughly 2-4″ right now. There is the chance it could be closer to 5-6″ in spots, but this will not be a major storm. Then, as the storm blows up exiting the New England coastal region, we could see some heavy snow fly back toward Boston and Eastern Massachusetts. I wouldn’t be shocked to see higher amounts there. Heavy snow will also fall in western Maryland and western PA and parts of WV.

Now heading into next week, the models continue to advertise a significant East Coast event. I’m not entirely convinced this will be a big snow event for anyone in particular. The three main models (Canadian, American, and European) all show the storm. The GFS is a little more suppressed, which isn’t abnormal. So it would just be a mild snow event. The European and Canadian models are much stronger and hug the coast. So what we have here is a situation. We’re a week away and we have a storm showing up, and it could be potentially strong. We’ve got it showing up a little further west than more recent big snow events on the whole. And we have disagreements on overall track.

So, I’ve gotten a lot of questions about next week. The bottom line: Way too far out to hype this thing. It could do any number of things. It could be snow, it could be rain, it could be a mix, it could be nothing. So stay tuned!

————-

State of Occlusion is on Facebook! I’ll post some additional cool links, quick model status updates, and snow maps early on that page. “Like” the blog by clicking here!

Here We Snow Again!

Snowfall Forecast for Tues/Wed.

There’s the snow map at the left. Here’s some ideas by region.

– Boston area could see some very high snow amounts of 16-20″, depending on the exact track of the storm. If the storm tracks just right, they could get slammed, as some models suggest. Interior Southern New England right now would appear to be the jackpot, but I wanted to emphasize the risk to the Boston area. Parts of CT and MA may see some 20″+ amounts, with generic 8-16″ amounts as you approach the coast (some coastal areas and the CT River Valley may see lesser amounts). Cape Cod will likely be close enough to the storm to mix or change to rain. This will cut down on snow amounts a bit there. Additionally, wind will crank on Wednesday, leading to blizzard conditions in parts of New England.

– Metro NYC area/NE NJ won’t be the jackpot this time around. However, this still appears to be a respectable, business hampering snow. Think of the last system that went through, think of post-Christmas, and expect this storm to end up somewhere in between the two. There will yet again be a very sharp cutoff to significant snows, somewhere within the I-287 corridor. Blowing and drifting snow will occur in this region Tuesday night and Wednesday.

– Southern NJ will be close to the center of the storm, so I do expect the possibility of a mix. It also appears the storm will really explode a little too far away from this area this time. I still expect a respectable 4-8″, with the potential for higher amounts in mainland Cape May, Atlantic, Burlington, and Ocean Counties (6-10 perhaps?). Coastal sections may even see less, primarily in Cape May County. If mixing for some reason does not occur, tack on an additional 2-4″ to these forecast amounts. Blowing snow will cause a few problems Wednesday.

– Philly/Trenton will be solidly in the 4-8″ range, with potential for higher amounts (8-12) as you get closer to Trenton/New Brunswick and slightly lesser amounts as you slide south and west of Philly. Blowing snow will be a problem on Wednesday.

– DC/Baltimore appear to be in the 1-4″ range, with again potential for higher amounts in the northeast corner of the map. Much of the interior back through OH/MI will average 1-4″ as well, with potential for a few 4-6″ amounts in spots, depending on how things shake out.

And that’s that! After this storm, it appears we’ll head into a relative period of calm in the Northeast. So enjoy this if you like big storms and snow. Winter is certainly not over though, so stay tuned.

————-

Just a reminder… State of Occlusion is on Facebook. I’ve posted some additional cool links, quick model updates, and snow maps early on that page. “Like” the blog by clicking here!

Norlun Troughs?

Going to get a little technical briefly. Going to put this pretty plainly: What’s coming Friday will more than likely not be forecasted very well. Why? We’re dealing with a phenomenon that’s pretty common in the Northeast in winter…it usually rears its ugly head at least once. We call this an inverted trough…Norlun trough…or instability trough. What is it? Well, typically, when you think of an atmospheric trough, you think of a “U” or “V” shaped pattern. In an inverted trough, this, well, inverts. It looks more like an upside down U. The lower pressure, or lower heights end up on the north side, rather than the south side. These sorts of setups can produce some nasty weather, heavy precipitation, and thunder.

Here’s more info on Norlun troughs (recognized in the 90s and named for the meteorologists who discovered it).
A technical paper on Norlun trough events.
And here’s more on inverted troughs.

So what’s it to you? Well, the models are beginning to hone in on how this storm on Friday and Saturday is going to behave. And they are indicating that an inverted/Norlun trough type setup may occur. The bottom line is that there will be snow. The question is twofold: Will the Norlun event occur, and if so, where will it setup? This morning’s models pegged it right over North Jersey and NYC. This evening it looks to be shifted a little further north. This is important, because outside of the Norlun trough there will be a generic sort of snowfall. But under the narrow Norlun trough, there should be significant snow, with the possibility of thundersnow and more.

Right now, the NAM model (a mesoscale, small scale, higher resolution model) is showing extremely heavy snow (and has on three straight runs today) for areas immediately north of NYC, Long Island, the Catskills, and the Western Mohawk Valley. The GFS model is suggesting this will be further north and east into New England and the Adirondacks.

Latest Snowfall Risk Assessment for Friday and Saturday

So my snow “assessment” has a broad area of potentially significant snow showing in red. I right now have this from about the Bronx, east-southeast into Long Island (yes, that places the division of snow vs. heavy snow within NYC). It stretches up into the western Hudson Valley, Catskills, western Mohawk Valley and southwestern Adirondacks. I also include much of southwest Connecticut as well, including Bridgeport and New Haven. The problem is that it’s next to impossible to pinpoint exactly where within this idealized zone the prolific snow will be. The yellow territory indicates the basic “cone of error” of sorts. I don’t foresee the risk of heavy snow shifting south of NYC much, if at all. The risk to me is clearly on the northern and eastern sides. This could shift further north, so the axis of the heavy snow stretches from Syracuse/Utica through Albany, the Berkshires, and Central Connecticut to the coast. And it could even shift further north too.

The heavy snow band will be awesome though, with extremely heavy rates of snow, likely some thunder, lightning, and whiteout conditions. I could see max amounts of 10-15″ in this band. You will only need to go a few miles from that core of heavy snow however to find amounts of 6″ or less…that’s the type of storm we’re looking at: Very narrow gradient, very sharp gradient, with extremely variable snowfall totals. Thus, this makes forecasting this system extremely difficult, if not impossible at this point. So if you live from NYC into Central New York and all of Southern New England, stay tuned. As I said, the forecasts for this will more than likely be challenging, vague, and possibly even wrong initially. But that’s the story.

Outside of the heavy snows, expect a brief period of maybe some heavy snow, with a coating or so, up to about 3″ in spots across much of NJ, PA and central New England. Closer to the heavy snow axis, there may be some 3-6″ amounts. But those will be isolated.

New model data indicating the possibility still of a major snowstorm Tuesday of next week. There are still a multitude of questions as to whether it will track in the sweet spot for a DC-Boston hit, as tonight’s GFS is showing, or if it will pass further south. More on that after this first event passes.

———–

Don’t forget, State of Occlusion is on Facebook! I’ll post some additional cool links and snow maps before they’re published here on that page. “Like” the blog by clicking here!