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

Cold, Flooding, Snow…Just Another Spring!

Trying to hit a few key issues today. First, the potential for accumulating snow in the Mid-Atlantic over the weekend. It’s snowed, sleeted, thundered, etc. across much of the Mid-Atlantic and Northeast in the last 36 hours…why not add something else to the mix?

12Z NAM Snowfall Forecast (From Earl Barker's Site: http://wxcaster4.com)

Map to the left is the NAM model depiction of snowfall for the next 72 hours. It shows you snow stretching from Omaha to Kansas City to St. Louis to Louisville to Cincinnati to just south of Washington, DC. This has been shown off and on throughout the week on all the models. It looks like we’re game on for a snow event. The problem is (of course) the exact storm track. The GFS forecast is *slightly* further north, which would bring more snow into DC and much less around Richmond. I would side in between the two right now…with light snows south of Baltimore to south of Richmond, with an axis of heavier snow, probably in the middle, through, say Fredricksburg, VA. Could be a decent event for the¬† northern part of the Blue Ridge. This will not be a *major* event, but given that it’s almost April, every snow event is extra painful.

So if you have weekend plans, specifically Sunday, keep this in mind. It is the time of year where it’s tougher to get snow to stick on the roads, but given that we’re leading into this event with several cold days, we could see more sticking than we normally would in late March.

In other news, spring may be delayed somewhat in the East. Just got a look at the latest weekly forecast from the European model…and, yeah, it looks cold if you live anywhere north of about Florida. Not guaranteed to verify, but this is certainly not what you want to see if you live in the Northeast, Plains, Great Lakes, or Mid-Atlantic.

However, this may help slow snow melt some over the northern tier…which is good because the latest river forecasts show major flooding likely on the Mississippi near St. Paul. Could be another painful Upper Midwest flooding season.

Follow State of Occlusion on Facebook!

Boxing Day Storm: TKO

As if dealing with some of the intricacies and inherent uncertainties of the weather wasn’t enough, you occasionally have days like today, where everything suddenly shifts and it looks like that monster storm you discounted yesterday may not be dead after all. And you start to wonder what has happened in 12 hours to completely change your thinking. And then the Hydrometeorological Prediction Center issues its discussion on the models and says this:

PREFERENCE: EQUAL BLEND OF THE 06Z GFS/00Z ECMWF OR THE ENSEMBLE
MEANS

INITIALIZATION ERRORS IN NUMEROUS DIAGNOSTIC
QUANTITIES...INCLUDING HEIGHT/VORTICITY FIELDS/RH...ARE EVIDENT IN
BOTH THE 12Z NAM/GFS WITH SMALL BUT LIKELY SIGNIFICANT SHORTWAVE
TROUGHS OVER SOUTH DAKOTA/NEBRASKA ALONG WITH
SASKATCHEWAN/MANITOBA...WITH THESE AREAS ALSO NOT PARTICULARLY
RESOLVED OR PREDICTED WELL BY THE 00Z ECMWF. THUS...THE SPECIFIC
PREDICTIONS BY ALL DETERMINISTIC GUIDANCE ARE IN QUESTION...WITH
THE RECOMMENDATION TO FOLLOW CONTINUITY...WITH THE FINAL OUTCOME
MOST BELIEVED TO LIE BETWEEN THE 06Z GFS AND 00Z ECMWF...WITH ALL
ENSEMBLE GUIDANCE INCLUDING THE SREF MEAN/GEFS MEAN/ECMWF ENSEMBLE
MEAN ALSO CONSIDERED USEFUL TO ADDRESS THE CONTINUED UNCERTAINTY.
THIS APPROACH DISREGARDS THE SUBSTANTIALLY DEEPER AND WESTWARD
SHIFT OF THE 12Z GFS REGARDING THE POWERFUL LOW TRACKING UP THE
EASTERN SEABOARD...AND TO A LESSER EXTENT THE 12Z NAM WHICH LIES
NEAR THE FAST EDGE OF THE GUIDANCE WITH THE DEVELOPING LOW

 

In other words, trust NOTHING. In reality, it’s more or less that there was a problem initializing both the NAM (short range model) and GFS model that was serious enough to make them believe that their solutions showing a much further west and stronger storm should be discounted completely. Basically, when the model is run, it’s run off of a snapshot of the atmosphere taken at the beginning…the initialization. If that’s significantly incorrect, you better believe the rest of the run of the model is also incorrect. So you literally trash it.

That said, there still will be a storm, and it still could be significant for a couple places, primarily southeast Massachusetts again, as well as potentially southeast Virginia and northeast North Carolina. There’s really not much else to say, except you’ll just need to keep an eye on things to make sure they don’t change…a 50-100 mile shift either way will shift those already tight banded snowfall amounts in one direction or another. But frankly, I’m not too worried about this one. So your post-Christmas return rush and Monday for the most part look okay, unless you live on Cape Cod. Forecast map is below (the Comic Sans font for the title was done intentionally to emphasize how much of a joke this storm has been)…not planning to do a new one unless there’s a significant change. I was a little generous with how far inland the “coating-inch” zone was. That’s mainly to account for remaining uncertainty. Many areas may just see flurries that don’t really accumulate. Only area I didn’t really look too terribly closely at is SE Virginia. Really seems to be a toss up there as to how much will accumulate depending on timing and track…could be more or could be less. We’ll see. Merry Christmas!

Snowfall Forecast Map for the Boxing Day Coastal Storm
 

PREFERENCE: EQUAL BLEND OF THE 06Z GFS/00Z ECMWF OR THE ENSEMBLE
MEANS

INITIALIZATION ERRORS IN NUMEROUS DIAGNOSTIC
QUANTITIES...INCLUDING HEIGHT/VORTICITY FIELDS/RH...ARE EVIDENT IN
BOTH THE 12Z NAM/GFS WITH SMALL BUT LIKELY SIGNIFICANT SHORTWAVE
TROUGHS OVER SOUTH DAKOTA/NEBRASKA ALONG WITH
SASKATCHEWAN/MANITOBA...WITH THESE AREAS ALSO NOT PARTICULARLY
RESOLVED OR PREDICTED WELL BY THE 00Z ECMWF. THUS...THE SPECIFIC
PREDICTIONS BY ALL DETERMINISTIC GUIDANCE ARE IN QUESTION...WITH
THE RECOMMENDATION TO FOLLOW CONTINUITY...WITH THE FINAL OUTCOME
MOST BELIEVED TO LIE BETWEEN THE 06Z GFS AND 00Z ECMWF...WITH ALL
ENSEMBLE GUIDANCE INCLUDING THE SREF MEAN/GEFS MEAN/ECMWF ENSEMBLE
MEAN ALSO CONSIDERED USEFUL TO ADDRESS THE CONTINUED UNCERTAINTY.
THIS APPROACH DISREGARDS THE SUBSTANTIALLY DEEPER AND WESTWARD
SHIFT OF THE 12Z GFS REGARDING THE POWERFUL LOW TRACKING UP THE
EASTERN SEABOARD...AND TO A LESSER EXTENT THE 12Z NAM WHICH LIES
NEAR THE FAST EDGE OF THE GUIDANCE WITH THE DEVELOPING LOW.

 


Monday Evening Storm Update

PSU E-Wall European Model Forecast for Next Weekend

So here’s my evening update on the storm and more. I won’t get to analyze the 00Z Euro til I’m at work tomorrow. But we can look at the 12Z Euro and the 00Z GFS. The 00Z Euro had backed off last night and sent the storm out to sea. This morning’s run was a little further West, but still primarily offshore enough to only impact the coast north of Delmarva with some light snow and hits Maine pretty good. The map to your left is the12Z run, showing the position of the low. Frankly, it’s not in a bad spot right now on the models. Sure, you’d like to see a big hit, but this far out (138 hours), I like having a track just offshore from my own personal experience. Last winter there were a few instances where the storm tracked like that this far out and then bounced back in the last 72 hours and ended up hitting. This is not last winter (despite the similarities), but still I like this. Again, the west will be what to watch…how the energy shoots in this week (almost a pineapple express scenario…not classic, but close) and how that weak ridge over the intermountain region sets up as well.

Watching the GFS come in and it’s clearly a bit deeper and wetter and probably further west, closer to the coast with this. The big, big question to me is what happens with this Pacific energy undercutting everything out here Thursday…the system actually goes into Baja, Arizona, and New Mexico, which is extremely odd to see in Nina I think. That’s your key right now, because it hits the block and explodes off the coast.

So the GFS is further west…good trend for snow lovers. Literal solution is mod snow for most of VA, southern 2/3 of NJ, and maybe Long Island/Cape Cod, with a secondary blast for Norfolk/NE North Carolina and Delmarva as the storm bombs offshore. This is really in the sweet spot this far out. Timing is Saturday night to Sunday, and again I think the key is almost entirely the energy in the Southwest. Stay tuned.