More Wintry Mayhem

This might be the worst period of travel of all the storms we’ve seen the last two winters. With 1,000 flights cancelled in Atlanta tomorrow, and the odds increasing that this southern storm is going to become a major Northeast snowstorm, airline schedules are going to be absolutely logjammed this week. This is looking ugly right now. Travel in the Deep South is becoming difficult if not impossible in spots. A stripe of 3-6″+ of snow, plus a stripe of 1/4-1/2″ ice accretion, and you have issues.

Snowfall Outlook for the Midweek Storm (Not a forecast)

My snowfall outlook for the Northeast is at the left. We’re still a solid 48 hours away from things beginning. But this is just meant to give you an idea of the highest probabilities of the highest snow. This is not meant to be a forecast and should not be treated like one. To sum up the models this morning: All models take the low and develop off the Northeast coast. Some are closer than others (NAM/Euro) and bring heavier precip. There’s going to be (again) a sharp cutoff of the western extent of the real heavy snow, vs. generic 3-7″ totals. There will also be a sharp southwestern cutoff to this as well.

So what does this mean? It means that in specifically New Jersey I think, there’s going to be a very sharp gradient that cuts off somewhere between Atlantic City, Trenton, and about Parsippany. North and east of that line, odds for heavy snow (6-12+) increases significantly. South and west of it, the odds drop off. It will be a little while before we can really peg that down. So for now, roughly from about NYC into New England stands the highest odds for significant snow. There is a strong possibility of a 12-18″ area of major snows, somewhere between the immediate north and east side of NYC into Southern New England. Mixing may cut down some totals in Eastern Long Island and coastal S New England, but for now, I just carpet bombed the whole area for potentially significant snows until we can know more. The DC and Baltimore areas, as has been the case most of this winter, look to get shafted by this storm, caught in between the developing coastal and dying inland low. I think this means 1-3″ at most, but we’ll see. Philly is on the cusp between the heavy stuff and nuisance stuff, so think 4-8/5-10 type snows for now.

Can things change? Yes. The NAM and Euro models are the beefiest right now in terms of heavy snow. In my opinion, they’ve had some strengths this winter, so I’m leaning more heavily on them together. The GFS model is a little too far offshore in my opinion, and thus produces lighter snow. The short range ensembles are also not very excited about this storm, but they also underestimated snow in the last event, so I would take them with a grain of salt.

So stay tuned, as there will be tweaks and changes, but I feel personally that this will be a nuisance event in DC/BWI, moderate event for Philly and South Jersey (potentially significant for the Shore), a significant to borderline major event for NYC, and a major event for much of interior Southern New England (some shadowing may occur in some areas, so it may not hammer ALL of SNE, but it looks promising to be good for many).

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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!

Polar Pain

First a quick reminder that S of O is now on Facebook, so if you haven’t already, “Like” the page, and I’ll be posting intriguing links from time to time, as well as posting snowfall forecast maps as needed a little faster than you’ll get them here. Click here to “like” State of Occlusion, and feel free to tell anyone you pass snow forecasts on to!

In what’s turning out to be quite an interesting winter across the entire US this season. We’ve had a blizzard in the Northeast, record low pressures in the Upper Midwest, a blizzard there too, one of the coldest Decembers on record in spots, snow in Vegas, graupel in Phoenix, and snow in many of the foothill and desert communities north of Los Angeles, record rainfall and snow in California, flooding in the Northwest, record brutal cold and snow in Europe, and on, and on. And that may have just been the appetizer.

6-10 European Ensemble 850 mb T Anomalies - Credit: Allan Huffman's Weather Model Site: http://raleighwx.americanwx.com/models

What’s coming over the next 1-3 weeks is nothing short of awesome to watch unfolding on the weather maps. Over the next 10-15 days there will be some of the coldest air of the season draining into the Central part of the country and possibly into the Southern and Eastern parts as well, at least 2-3 *chances* at storms in the Northeast/Mid-Atlantic, the potential for the Southeast as well, and possibly even a winter storm deep into Texas. All *possibilities* in this pattern.

The image I posted (click it or any other image to enlarge) is a map from Allan Huffman’s model site (http://raleighwx.americanwx.com/models), which illustrates the European ensemble mean 850 mb temperature anomaly over the period 6-10 days from now. Basically, just an average of how much warmer (yellow) or colder (blue/purple) than normal this model is predicting over the period 6-10 days from now. And notice how almost the entire US (except Maine) is in the below normal range. Keep in mind, 850 mb temperatures are just temperature about 5,000′ above sea level. Translate this down to the ground and under clear skies and/or calm winds…that is cold, even for January, even for these areas. Also keep in mind that these temperature anomalies are in degrees C, not F, so 23F colder than normal aloft could be 30-40+ degrees colder than normal at times on the surface. And I’m not posting it, but the 11-15 day forecast looks equally as cold, if not even colder.

Does it get any better? One of the main drivers (probably the easiest to explain, but certainly not the only driver) is the Arctic Oscillation, or a measure of atmospheric blocking in the Arctic region. High pressure can set up there aloft, and it basically displaces the cold air that’s supposed to be there and dumps it southbound into the US, Europe, etc. The AO tanked in December and really has not recovered, and it seems to be reinforced this month. This happened last winter and helped make it one of the colder winters in recent years for the Southeast and parts of the Central US. This looks as impressive as anything that was seen last winter or this past December. Coupled with things we’re seeing elsewhere, this adds up to what looks to be a long-duration and impressive period of cold in the US. The biggest question is whether or not the extreme cold can spread south and east far enough to impact larger population areas. But for the Northern Rockies and Northern Plains, this looks awful.

GFS Forecast for Saturday Morning, credit: NCEP

So what about snow? This will be the more challenging forecast to make. The map to the left is the GFS forecast for this coming Saturday. Last night’s European model absolutely bombed areas from Baltimore northeast into Boston with extremely heavy snow. Today’s GFS tries to do something similar, displaced further north a bit and behaving differently. This is the first of several threats. I’m not on board with this being a major storm at this point, but a weakish “clipper” type system with a widespread light snow, isolated pockets of heavy snow (potentially a squall line type of scenario with embedded thunder as it moves through NY/PA and New England). Right now there’s a low risk of this being a big system for most of PA/NJ and south, and a medium risk for New England. Stay tuned.

GFS Forecast for Next Wednesday Evening, credit: NCEP

The more important storm comes early to middle next week. The image to the right shows the GFS forecast for next Wednesday evening. Depending on how things play out over the next week, this one could be the one that presents a major threat to the I-95 corridor again. There are threats beyond that, but primarily for Texas and the Deep South….in other words, it may be “too cold to snow,” as they say.

I’m going to be non-committal on any of these threats at this time, but if you live in the Northeast or Mid-Atlantic, keep an eye on this Friday-Saturday and next Tuesday-Thursday, and load up on cold weather essentials…when us as meteorologists start saying that the winter weather is interesting, that’s usually not a good sign. I will keep you posted however.