What Went Wrong with Winter 2011-2012 for Snow Lovers (and Right for Snow Haters)

Good Sunday evening.

As February draws to a close, I’ve decided to take a look back at the Winter – or essentially non-Winter – of 2011-1012, with an emphasis on why we saw such an extensive snow drought.

Here’s a map of the current snow cover across the lower 48 as of today:

And for exactly a year ago:

It’s easy to see that we’re far below the level of snow  cover when comparing this year to the prior. This year, the deepest snows are confined to northern New England, the upper Great Lakes, and the higher elevations of the central and northern Rockies and Sierra Nevada and Cascade mountain ranges out west, while last year, essentially the entire northern half of the country was covered by a decent snowpack.

So how is this year different from last? The are a lot of factors, but I’m going to try to simply it to just a few, which I believe are the most important.

The first factor is the El Nino Southern Oscillation, or ENSO, which fluctuates from:

(1) El Nino, where the equatorial waters of the Pacific west of  South America are warm, as depicted by the bright white shading below,

And (2) La Nina, where the waters are cold, as shown by the blue and purple shading:

This year was predicted to be a weak to moderate La Nina, which in fact was pretty close to what verified:

On the graph above, the line through the center is a neutral (or La Nada) ENSO state, whereas the red peaks are El Nino’s, and the blue troughs are La Ninas. One can see how this year was in fact a weak to moderate La Nina (last trough to the right on the graph), and the year before was an even stronger La Nina (second to last blue trough). La Nina’s generally favor warmer conditions along the East Coast, colder conditions across western Canada, including Alaska, as well the Pacific northwest:

It’s hard to argue those facts this year. Alaska had record cold and snows, and well, the East Coast was very far from anything like that. But what gives? 2010-2011 was a La Nina as well, and stronger at that, and the results were much different. There have to be other factors involved, and this is why you can’t define the winter based on the ENSO state – it’s just not that simple.

Another important factor which has garnered significant attention in the weather world over the past several years is the North Atlantic Oscillation (NAO).  Those that follow me will recall the NAO is an index which measures the degree of Greenland blocking (in the form of a ridge as seen below) which slows storms down and prevents them from quickly exiting the east coast.

Such a negative NAO, as seen above, promotes a storm track along and paralleling the coast, as well as an increased threat of Arctic air intrusion into the eastern US.

A positive NAO means there is a lack of blocking, the ridge is displaced to the east over Europe, and storms race due east and out to sea, in progressive manner, with the majority of our cold locked up to the north.

Unfortunately for snow lovers, this year has featured an extended positive NAO, exactly the opposite of the previous 2 years:

So, in a weak to moderate La Nina year, the lack of blocking or positive NAO we have had for most of the winter has had a pronounced effect in our overall lack of winter weather.

But there have been other factors as well. The Madden Julian Oscillation, or MJO, has been another major player this year. The MJO is not a standing pattern such as La Nina or El Nino; but rather, it’s a traveling pattern characterized by an eastward progression of large regions of both enhanced and suppressed tropical rainfall, observed throughout the tropics, but mainly over the Indian and Pacific Ocean.  It is divided into 8 phases, each corresponding with the geographical location of the active phase (or greatest convection/rainfall) of the MJO:

Phase1 includes signals both from the initiation of an MJO event in the western Indian Ocean basin and the breakdown of MJO events in the mid-Pacific Ocean. During phases 2 through 8 the MJO travels east at 4-10 days/phase.

To put it more simply, think of phase one of the MJO as a large string of thunderstorms dying in the mid Pacific ocean, and re-firing in the western Indian Ocean. Then, every 4-10 days, this active center of thunderstorms propagates east across the tropical Indian and Pacific Ocean, as the MJO advances from phases 2-3-4-5-6-7-8-1 above on the map, and the cycle can then repeat itself. These thunderstorms can vary in intensity, and can die off at any point in the cycle of the above 8 phases. For example, the MJO may start in phase 1, and every 4-10 days advance through phases 2-4, and then weaken or die off completely. They may re-emerge in the same location for phase 4, which is in the region of Indonesia, or may go back to phase 1, or any other phase for that matter.

As you can imagine, this is extremely difficult to forecast, given the high variability. An example of a plot for the MJO can be seen here:

It’s a little busy, I realize. But the number in each of the 8 octanes represent each of the phases of the MJO. The plotted line shows where the MJO wave has been for each day of the past 40-45 days or so. This line cycles in a counterclockwise fashion as the MJO propagates through each of the phases discussed above. Currently we’re in phase 2, and by simple logic, one would expect the MJO to progress into phase 3 and 4 over the next 8-20 days, as is seen by the GFS model forecast plot:

Notice the GFS has the line going towards the center circle of the chart after going through phase 4 – this reflects what can happen when the thunderstorms weaken or even die off completely. It may stay rather dormant, can re-emerge in phase 4, or in any other of the 8 phases.

So, why the hell is this so important? I mean, it’s half way around the world, it’s very confusing, and we don’t forecast it very well.  The reason is simply this – because each of those 8 phases has a rather strong influence in the weather here more locally in North America during the winter months of January to March, as illustrated by the graphic below:

The maps above represent the temperature composites across North America from January to March for each of the phases of the MJO. As you can see, phases 8, 1, 2, and 3 correlate with colder temperatures for the east coast, while phases 4, 5, 6, and 7 are significantly warmer for those of us in the east. With that information, take a wild guess as to what phases we’ve spent most of the winter in – and here’s a hint, it wasn’t the first group. And for bonus points, guess what phases we were in the majority of the winter of 2010-2011 (that’s right, it was the first group).

So keeping track so far, in this winter with a weak to moderate La Nina, we have had a mostly a positive NAO, and  lack of blocking, and an unfavorable MJO. 

And finally, we come to the Pacific. The pattern over the eastern Pacific has been rather dreadful all year. We’ve been largely stuck in a progressive, fast paced flow in the upper levels of the atmosphere:

This firehouse of warmer Pacific air has kept our temperatures rather warm for nearly the entire winter. True Arctic air has been bottled up in Canada and Alaska, minus a few days here and there.

This of course is a somewhat simplified (and I know, some of you are thinking this post was probably too complicated) look at what went lead to the lack of winter weather for 2011-2012. The largely positive NAO, unfavorable MJO, and poor Pacific pattern have all had a hand in it.

La Nina is starting to fade and we will likely be in a weak El Nino come next winter. What does that mean? Well, we’ll leave that for a future post. For now, I leave you with what I always think of whenever I hear the words “El Nino:”

President’s Day Weekend Storm – What’s going wrong for those in the Northeast

Good morning.

At first glance, the enhanced water vapor loop below would probably have snow lovers in the northern Mid-Atlantic and the Northeast jumping for joy. An active subtropical jet stream streaming across central and southern Mexico is acting like a fire hose and injecting a tremendous amount of moisture and energy into a developing storm moving northeast over south Texas. Normally, in the winter, that would mean a serious winter storm threat for those in our area. But unfortunately, there are several factors stacked against those north of the mason dixon line for significant, if any snow.

Let’s look at this morning’s upper level map from the 6z NAM model run:

There are 5 features that are important with regards to the behavior and development of this storm (or non-storm):

 

1. The initial southern jet stream shortwave energy responsible for the storm itself, now over southern Texas. This area is easily seen on the water vapor (WV) loop above.
2. A pretty potent shortwave over the Great Lakes, also well seen on the WV loop.
3. A small focus of energy from the northern jet stream over Nebraska. This is a little harder to see, but is the small swirling area over southwest Nebraska with a darker green center.
4. Energy associated with a large low pressure system over the Pacific northwest, which is only partially visualized on the WV loop above, but not hard to pick out.
5. An area of confluence, represented by the two red lines on the upper level map, and the streak of blue on the WV loop above. Confluence just refers to winds that come together or meet up. You can see on the upper level map that the lines (representing upper level winds) that bend up over central Canada come down and meet up with the lines bending down over Texas in the Midwest region. This is important because confluence is not a good thing for promoting precipitation. The sinking air that results chokes off precip, and in some cases it can be pretty abrupt.

The upper level map above corresponds to the surface map below:

And this morning’s radar, which is pretty impressive by the way:

You can see above that the area from the central plains to Ohio is devoid of precipitation – that’s the result of the confluence I talked about above. The precip shield is hitting a brick wall from central Kansas to central Missouri. This is very important with regards to our weather tomorrow.

Now back to those five feature describe above:

The map above is the forecasted upper level pattern for tomorrow afternoon around 2 pm. I know it’s a little busy, but I’ve tried to simplify it as best I could. By this time, the energy from Texas on the previous map (#1) is trying to combine or phase with the energy that was over Nebraska (#3).  This causes a deeper trough, or U shaped structure, over the southeast US, and rising heights, or upper level winds to flow southwest to northeast, along the east coast.  Normally, this would carry our developing low pressure area straight towards us. But there are two problems. First, the energy over the Great Lakes on the previous map (#2) has now become incorporated into a 50/50 low (so named because of its position at 50 north, 50 west). This (A) prevents our storm from climbing up the entire eastern seaboard, and (B) creates confluence right in our backyard.  Think of it like two opposing magnets – they bounce off one another.

The low is only able to gain a certain degree of latitude, and then is forced off the coast. The second problem is the energy in the Pacific Northwest we talked about earlier – it’s racing in behind our storm. The low over the southeast climbs to a position to northern Georgia, hits the resistance from the 50/50 low, and is pushed out by the energy to our west, or kicker, due east, off the southeast North Carolina coast.

So, in the end, we’re left with some clouds and not much else, while eastern Kentucky, West Virginia, and a large part of Virginia see significant snows.

Can this change? Perhaps. If the energy over the Great Lakes moves out faster, the 50/50 low is weaker or further east, or the kicker system is a little slower, this could bring the precip shield up into our area enough for a few inches of snow. The 12z NAM just came in a little further north, and brings some light snows into the southern 1/3 of PA. I’ll be watching the next few model runs through this evening and will let you know if there are any major changes.

Later…

FINAL CALL FOR 1/21/2012

This will be a moderate snowstorm, with most of the area receiving a general 3-6 inches of snow, with some local amounts to 8 inches. There is a small chance it could go a little higher, with possible banding towards the end of the storm late tomorrow morning, but for now I’m happy with this map, which was also posted on Lehigh Valley Weather Patrol on Facebook.

 

FIRST CALL FOR FRIDAY NIGHT TO SATURDAY EVENT

This was issued last night around 6 pm on our sister site, Lehigh Valley Weather Patrol on Facebook, in collaboration with the chief meteorologist Bobby Martrich. I’ve believed the models are underdoing the cold air currently coming into the Midwest – this is fresh Arctic air, and the storm will likely be colder than modeled. In fact, the overnight model runs have done just that, and these amount may be a little too low, and another inch or two may be added to the totals below. More later today as new information comes in, but it looks like the first real snowstorm of the winter season will happen this weekend.

INCREASING THREAT FOR MODERATE SNOW EARLY THIS WEEKEND – WHAT ABOUT FEBRUARY?

The overall theme for the past few days has been MUCH colder, with below zero temperatures for portions of the northeast as well as very heavy lake effect snows over the past 72 hours, both of which have not been seen much at all so far this winter. After a brief warmup with some rain tomorrow, the colder weather will return, as well as an increasing THREAT of a moderate snowfall (3+ inches) Friday night into Saturday for the Mid-Atlantic north of the Mason-Dixon line. This will precede a significant warm up the following week (Jan 23), which will last about 5-6 days. The pattern for February is becoming more and more interesting, as there are signs of a negative NAO and Greenland blocking returning for the first time this winter. This was the wildcard I had discussed in my last in-depth post, and if this should occur, would mean a greater chance of bigger east coast snowstorms. I’m going to try to post a more in-depth discussion in the next 1-2 days, after a few more model runs and more in depth analysis – being on call this weekend has taken its toll…

PATTERN CHANGE ON TARGET – WHAT TO EXPECT

I must warn you this is a rather along read, so I apologize in advance.

First of all, in my previous discussion I talked about the possibility of one or two storms affecting us around the 8th and 12th of January. It appears there will be only one storm, and it will likely be a big rain producer for anyone from the Appalachian mountains east, which would include I-95, mid week next week. It could end up being a VERY powerful storm, as is often the case with storms that immediately precede pattern changes. However, after that, well, let’s just say after that it looks like winter is coming back with a vengeance.

Let’s review a few things that were discussed in the previous blog.

The biggest key to this pattern change is the sudden stratospheric warming (SSW) event, which is PRESENTLY very impressive:

Remember, that warming over Alaska breaks down the cold polar vortex that’s been stubbornly present there for the last several weeks, and has prevented true Arctic air from invading the U.S. for any sustained period of time, and instead flooding North America with relatively mild Pacific air:

But, with that warming over Alaska, the vortex breaks down and retrogrades west, allowing for ridging and development of cross polar flow, bringing Arctic air into North America including the northern U.S.:

You can easily see the ridge over Alaska. But look at Greenland. There’s no ridging – YET. What do I say yet? Well, because the European ensemble model run from yesterday is advertising an even bigger SSW event in the coming days:

That bright white shading over the pole is literally off the scale regarding the degree of warming. More importantly the area which is warming now includes Greenland. Just as the ridging developed over Alaska due to the current stratwarm, warming over this large of an area including over Greenland would result in ridge, and blocking along the East coast of the US:

This blocking prevents storms from exiting the eastern seaboard stage left. Currently, we’re in what’s called a very progressive pattern – storms come and go in a matter of hours, and cold snaps and warming periods last a matter of days. But with blocking, everything slows down. The Arctic air is funneled across the north pole and into the central and eastern parts of North America, and it sits. Meanwhile storms come along and are prevented from quickly moving out to sea, increasing our chances for snow, and in some cases big snow events.

But there’s more at work here than just the SSW event, ridging in Alaska and Greenland, and the negative NAO. We’re currently in a weak, east based La Nina. La Nina refers to cooling of the waters in the eastern Pacific ocean, which has a profound impact on the weather pattern over North America. I’m not going to go into an entire explanation on the El Nino Southern Oscillation (ENSO) here, that’s another discussion for another time. But just so you know what I’m talking about, here’s another pretty picture:

This is in contrast to El Nino, as depicted by the late Chris Farley:

I can never get enough of that.

There are two relevant things one needs to know when it comes to a weak, east based La Nina and this pattern. The first is the southeast ridge, which will fight the cold air bleeding in from the north – remember the picture above:

And the second is the subtropical jet (STJ) stream:

which is relatively active BECAUSE the La Nina is indeed weak. If this were an El Nino, the STJ would be raging, becuase the WARM waters of the eastern Pacific allow for greater convection in the eastern Pacific. That being said, a weak La Nina allows for some convection, and an additional source of fuel for storms as they cut across the southern US. Look at the convection currently in the eastern Pacific west of Mexico:

The southeast ridge will fight back against the advancing Arctic air, while the STJ provides an extra fuel source.

Here’s a modified image from the afternoon run of the GFS, for next Thursday morning, to tie everything together:

Now, first of all, I’m not saying anything is going to happen next Thursday. I just used this image as a way to illustrate what I’m talking about here. The arctic air and southeast ridge will be at odds, creating a storm track somewhere between TX/OK and the Mid-Atlantic/eastern New England. Where exactly this sets up is still a little up in the air, but you get the general idea. Storms will be able to gather moisture from both the Pacific (via the STJ) and the Gulf of Mexico (also courtesy of the southeast ridge).  As blocking develops later, the storms slow down and can’t exit as quickly as they have been doing. The warm air from the south rises up and over the colder Arctic air just north of the storm track, causing overrunning precipitation:

Notice how there’s not just snow in this depiction. Ice is also a possibility. But in areas where the precip remains snow, it can really pile up, even though such storms aren’t true nor’easters, at least not to start. The President’s Day Storm of 2003 was largely an overunning event:

Again, this is for illustration purposes only, to show potentially where this pattern could go. I’m not saying something like this is a certainty, but it can happen.

So that’s it for now. Currently I expect a large, probably pretty powerful rainstorm to affect the eastern US mid week next week, followed by Arctic air, which should be sustained rather than transient starting late next week into next weekend. And then the real fun should begin.

Winter is far from over.

INCREASING CONFIDENCE IN A REAL PATTERN CHANGE – HOW WINTER WILL MAKE A COMEBACK

It’s been a while since I’ve done an in-depth blog on winter weather for the area, but there’s a reason for that – there hasn’t been much to talk about. That appears to be changing over the course of the next 1-2 weeks. Let’s dig into it….

First of all, there is a significant stratospheric warming event that has and is currently occurring, as discussed in my blog from yesterday. I like lots of pretty pictures, so I’ve included a few to get my point across:

The image above I posted yesterday. I think everyone can see the warming taking place on the upper left hand part of the figure. These same areas were a good 30 degrees Celsius lower just a few weeks ago. But the cine loop below has an even bigger visual impact:

You can clearly see rapid warming occurring over northeastern Siberia, the northern Pacific and Alaska, and northwestern Canada. Keep these areas in the back of your head for later in the discussion.

Let me say, this is an impressive event. There were some hints on the models back in late Noevmber of this occurring, but it took much longer than anticipated – the stratosphere started out unusually cold this year. However, it IS occurring and therefore it’s the first OBSERVED positive sign that things are truly changing. Of course, the next logical argument is – does it translate down to the troposphere, or the lower portion of the atmosphere, where we live? It doesn’t always have to happen. But given the rapid warmth that is occurring, I believe it will.

The models I believe are already starting to pick up on this. The lag time between a sudden stratospheric warming (SSW) event and changes in the troposphere can be anywhere from 1-3 weeks, depending on what you read. Now remember the location of the warmest anomalies above? Here’s another global perspective to refresh your memory:

Again, over northeast Siberia, Alaska and the northern Pacific, and northwest Canada. Remember the lag time discussed above, look at the GFS ensemble forecast for about 3 days from now:

There is a stubborn vortex over Alaska (dark blue blob) , which is is one of the reasons why Arctic air has been locked up in Canada for the past several weeks, to the dismay of snow lovers on the east coast. This combined with the vortex over northern Canada effectively blocks any true or sustained arctic air from entering the United States. The result is transient cold shots of modified Pacific air, as evidenced by the upper level winds blowing from west to east.

Now lets look at the ensemble forecast for about 2 weeks from now:

A ridge has now formed over the exact position where the stratospheric warming is taking place, as the warming effectively breaks down the vortex.  This allows for a cross polar flow of Arctic air from Siberia to directly discharge into the northern United States. Although the trough axis is centered in the western US, the coldest air is actually centered farther east towards the middle of the country because of the cross polar orientation. The cold then bleeds east over time. This bleeding of cold air in conjunction with the warming southeast ridge which has been prevalent this year because of the weak La Nina, creating a gradient for storms to travel along, roughly from Texas to the Mid-Atlantic and New England states. Moisture from the southern branch of the jet stream is also a bigger contributor this year due the the relatively weaker La Nina when compared to the last. This situation is a much more wintry scenario than what we’ve seen thus far, setting the stage for overrunning snow and ice events in the coming weeks right through February. Notice I included ice, and not just snow, in the equation – these will not be the snow or no snow storms we were used to in the past. Those to the north of the storm tracks will see more frozen precipitation, while those farther southeast will see more of the sloppy variety.

Now, the models are just starting to see this change. It will play itself out over the next week to 10 days, assuming the SSW event does indeed affect the troposphere, ridging develops near Alaska, and cross polar flow develops, providing a source for cold air, which we’ve lacked for just about the entire late Fall and Winter season so far. I know there will be skeptics out there, saying they’d heard the same thing for weeks. But remember, this is the first time we have actual evidence that the stratosphere has warned SIGNIFICANTLY. This is conjunction with model solutions which correlate with what we’re seeing presently is what’s important. All the other theories on when the so-called pattern change would occur (if ever) were based upon model forecasts of the SSW event, not observed data.

So, what about the more immediate future? There appear to be two potential events on the table, one around January 8th (this Sunday), and the other around January 12th (Thursday). The first is showing up on the European, GFS, and Canadian models. The second is seen on the Euro and GFS, but out of range on the Canadian.

1/8/12 Euro:

1/8/12 GFS:

1/8/12 Canadian:

And then the 1/12/12 event:

Euro:

And finally the GFS:

Now, I’m not big into details this far out. But both storms take a general track from the Texas and lower Mississippi valley into the Mid-Atlantic region. Both will have rain/snow line issues, and in fact one or both may indeed be too warm for I-95 for much (if any) snow at all.

Let’s look at the North Atlantic Oscillation index:

There are two relatively distinct dips toward negative to slightly neutral which roughly correspond to the time periods in question. Additionally, there is relatively good agreement among the ensemble members during this time period. This lends more credibility to the two storms in question. It also provides some hope to those along I-95, lessening the threat of a coastal hugger or inland storm, which would bring rain (although it still may not be enough).

I’m not completely sold on either storm being big snow producers for the Mid-Atlantic or New England just yet. These storms may actually precede the above described pattern change that is anticipated. Given the current SSW event, the lag time, and what has been showing up on the ensembles, the actual transition to more constant colder and more wintry weather may not happen until the second half of the month. But based on the changes discussed above, I believe it is coming.

One more thing, as I type this, the new CFSV2 weekly forecasts have dramatically flipped to a colder solution, in line with the GFS ensemble run I’ve posted above, courtesy of Joe Bastardi’s recent tweets:

You can see how this nearly matches the GFS ensembles in about 14 days:

And results in the week 3 temperatures as below:

The blue is very cold air. Take my word for it, this is much colder and a complete flip from what they were showing on the last run. This NEVER happens, and only further confirms my suspicions that the models are picking up on the change at hand.

Winter is not dead, it just took a break for the first half. I expect a change to more classic winter weather for the second half of January and into February.

More on the upcoming storms discussed above during the next few days as warranted.

Stratospheric warming is FINALLY occurring….

This figure above shows there has finally been a significant stratospheric warming event in the last few weeks – the temperature of the upper atmosphere has warmed over 30 degrees Celsius since mid December. You can see just how cold the stratosphere was for the past several months – a finding which is not generally conducive to winter weather. 

This warming should displace the polar vortex, or markedly cold pool of air residing far to our north, farther south and put more arctic air on the table for the United States, something that has been non-existent for the last few months. This will increase our chances at snow. The first threat looks to be around the January 8-12th time frame, but I want to see a little more consistency among the models before I discuss it in more detail.  More later…

FINAL CALL – DECEMBER 6, 2011

This will be the final call for the storm occurring tomorrow (Wednesday) night. Please realize this storm will start out as a heavy rain, and transition to heavy snow rather quickly from west to east from late evening to midnight. Snow will continue for only 5-6 hours or so, but it will be very intense, with rates of 1-2, maybe 3 inches/hour, and possible thundersnow. This will result in very hefty accumulations in a very short time. Where banding does occur, the higher amounts are possible. The storm will be over by Thursday morning. There is the chance of more (albeit likely less) snow towards the weekend, but one thing at a time.

BEYOND THE MODELS – CHANGES IN THE QBO AND STRATOSPHERE AND THEIR IMPLICATIONS

This is a repost I did from yesterday from liveweatherblogs.com, but it’s very relevant this morning as some of the models are beginning to pick up on what I discuss below. It’s a bit technical, and more for the hard core weather enthusiast (nerd), but I’ll try to simplify it some so that most will understand.

Since people continue to follow the ups and downs of the models, including teleconnection forecasts like a yo-yo on a string, I wanted to get away from that this morning and briefly explain why I’m not as pessimistic as some on the winter as a whole, including December.

Two days ago, I stated that “the QBO continues to fall and stratospheric temps continue to rise, which mean eventually the Polar Vortex will slide south. Eventually the NAO and AO will go neutral to negative due to this, based on physics.”

But what exactly does that mean?  Here’s an excerpt from Steve DeMartino’s discussion from yesterday morning, which sums it up well:

“when the QBO is negative at a level, that means the warmer stratospheric air at the tropics can be transported at a much faster rate into the northern latitudes.  The warming leads to expansion of that level towards the surface, which leads to a cooling effect on the troposphere, where we live.  Under areas of strong stratospheric warming, deep upper lows develop.  A negative QBO phase leads to the Polar Vortex to drop south and strongly supports a negative AO/NAO pattern.”

Here’s the latest cine loop showing stratospheric temperature changes across the globe:

You can easily see the warming taking place at the upper latitudes (at the top of the image above), because the QBO index continues to fall. I’ve simplied this a little, but the bottom line is the NAO and AO should improve as we go through December. Just looking at the GFS through 384 hours and it’s teleconnection forecasts doesn’t cut it for me. If you look beyond these, I think it helps. The GFS has in its defense trended colder, the NAO is on the downturn on the latest GFES forecast:

One could argue that the teleconnection forecasts have been all over the place the last few weeks, which they have, so why believe them, but with the above evidence I’m more inclined to believe them this time around than not. If you look at the cine loop above for mid  November, the stratosphere was pretty cold – favoring a positive NAO. Now that the startosphere is warming, this should, and the NAO should head toward neutral and then weakly negative. We’ll have transient cold, and nothing extremely warm, for the next 10-14 days, and even a chance of some snow for those farther north. After that, we’ll know a lot more, and we should be in a pretty good spot if things unfold as I think they will. Will the blocking be like the last two years? It very well may not. But there will be some. Which is why I still believe those farther away from the coast will benefit the most this time around. 

The bottom line is this – it will become much colder mid week next week, with a chance at some snow with minor accumulations in the Wednesday-Thursday time frame in at least east central and northeast Pennsylvania. The cold will be somewhat transient at first, but if I’m right about the above, should be more prolonged for the second half of the month, with increased chances at bigger snows. A white Christmas is a definite possibility for a lot of people in eastern PA.