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!

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Historic (?) Southeast Storm Could Be Next Northeast Snow Threat

Overall pleased with the forecast for the current storm for the Big Cities. Definitely underestimated parts of CT that saw 8-16″ of snowfall on average in the western part of the state, even down to New Haven County. Just a reminder… State of Occlusion is on Facebook. I’ve posted some additional cool links and snow maps early on that page. “Like” the blog by clicking here! On to the fun…

The Eastern 2/3 of the US are going to be peppered by winter events over the next five days or so. Let me run through things here.

Snowfall Forecast from Friday Overnight-Sunday Morning

First off, tomorrow, as all of the energy responsible for the unsettled eastern weather the last couple days starts to slide offshore, it will begin to develop into a nor’easter, but rapidly exit to the east. However, as it intensifies, it could produce a pretty well organized band of snow from about Southern NJ/Central DE through E Long Island and possibly Cape Cod. The snow map is over to the left if you want to enlarge it and see my thoughts through Sunday morning. Not a big storm, but there could be some heavy snow for an hour or two, especially east of Rt. 206 in NJ as the storm pulls away. Lingering snows will produce perhaps a couple more inches in New England, with upslope areas of the Green Mountains and Berkshires more favored. I don’t believe accumulations will be that high. There is some chance the Cape and Islands, as well as the Boston area may see some enhancement too.

GFS Forecast of Total Ice Through Tuesday Morning (Credit: wxcaster.com)

That will exit tomorrow night and by Sunday morning or so, things will be quiet. But that sets the stage for the next event, and this one might be an absolutely punishing doozy of a storm. The map to the right shows the GFS forecast for total accumulated freezing rain through Monday. A strong storm system is going to trek across the Southeast in an unusually cold air mass, and with it will come plenty of moisture…almost an El Nino type storm. Winter Storm Watches are posted almost to the Gulf Coast for Mississippi and Alabama, and for most of northern Georgia and Louisiana, as well as Arkansas. This amount of ice this far south would be absolutely crippling…that isn’t hyperbole either…these are places that almost never see frozen precipitation of any kind, let alone to this extent. The raw model outputs in some of these places is absolutely mind boggling. Atlanta is showing anywhere from 6-12″ of snow, with 1/4″ of ice! Of course, that’s raw model and has to be taken with a grain of (road) salt. But still, that’s absolutely insane, The all-time snow record for Atlanta is (I believe) 10″ in January 1940. It’s tough for me to put this in historical context, as I’m not THAT familiar with Southeast wintry climatology, but this would be, from a meteorological perspective, one of the most incredible things we’ve seen over the last couple winters (and we’ve seen a LOT). Check out the total snowfall forecast through Tuesday morning in the Southeast below (from http://wxcaster.com/regional_snowfall.htm).

Southeast NAM Snowfall Forecast Thru Monday Night (Credit: http://wxcaster.com/regional_snowfall.htm)

The next question becomes, where does it go? The three main models to look at for tonight, taking them (since the NAM only goes out 84 hours) to Tuesday morning shows the low sitting somewhere off the northeast South Carolina coast. Not surprisingly, where this storm sets up, will determine how it impacts areas up the coast. The European model sets up the furthest northwest. Not surprisingly, as you run it out further in time, the European delivers a quick moving, but solid snow event (6-12″ish) for most areas from I-95 south and east. The GFS is a glancing blow, but mainly a miss (not bad for New England). The NAM stops at hour 84, but is a little closer to the European model than the GFS. So my feeling is that despite model flip flopping the last couple of days, we could still see a pretty potent little storm from the Carolinas up into New England. The timing on the snow would be later Tuesday to the south, ending Wednesday from Jersey through New England. Stay tuned on this, especially if you have midweek plans. I’ll do my best to keep you posted.

 

Threat for Next Weekend Remains

PSU E-Wall 00Z GFS Forecast Next Sunday Evening

I’m a major proponent of NOT hugging models, but there’s no question that tonight’s 00Z GFS run was encouraging. The map to the left shows the GFS forecast for next Sunday evening. Keep that in mind…that’s a week away. We all know how fast that can change, but to see both the Euro and GFS in agreement on an approximate track/style of storm here is encouraging. Taken literally, this would be a significant snowstorm from DC-Boston and for most/all of NJ. I wouldn’t take things literally, but I want to at least bring the idea that this is a possibility to your attention.

We’ve got a ton of energy swinging into the West Coast, and ultimately that’s going to be the key to this I think…how that energy gets directed inland and across. And a couple things to note: Models notoriously handle this sort of energy infusion into the Pac coast poorly. And the ridge in the West is a bit flatter and less amplified than I’d really like to see to generate a big East Coast storm. So the big problem with seeing a great storm like this seven days out is that everything can go wrong between now and then. More on this in the coming days.

One thing the GFS certainly does though is continue to provide reinforcing shots of cold weather to the Eastern half of the US through the end of the year. Obviously, that’s something else you can’t take literally, but winter doesn’t seem to want to let up. And with the off the charts AO and strong NAO blocking in place, this makes some sense. Stay tuned.

Lastly, cool video to end tonight that I just found. Heavy rain in Washington State and the Northwest has produced significant flooding around Seattle and elsewhere. Here’s video of the Stillaquamish River at Granite Falls in Washington…flooding…and this is absolutely massive.