Messy Evening Commute

Just in case you forgot, we have not reached 32 degrees for over 180 hours now, dating back to last Sunday! Although I am sure that most of you already knew that it has been damn cold. Well, that cold air is about to finally retreat back into Canada. But not before we get a poorly timed few inches of snow.

One look at the current surface temps in the US will show you the large divide between the cold air and the warm air. The surge of warm, moist air has overtaken much of the Midwest and is heading our way.

Some of that warm air will begin to leak into New England today. Remember, warm air is lighter than cold air. And this cold air we've had for 8 days really doesn't want to leave quietly! So that surge of warm air will ride over the surface cold air and creates this.

All of the leading precipitation is snow, which will be ours to deal with sometime after 4PM. Bad timing. We aren't talking about a blockbuster storm here, generally 1-3 inches for most. But we all know that any snowfall that starts at the same time as the commute does creates big time problems. Expect a slow go of it tonight.

Notice the pink color on the image above. That denotes mixed precipitation. Eventually, the warm air will intrude at all levels of the atmosphere, including the surface. So we should all change to a sleet/freezing rain mix after midnight tonight and early tomorrow morning. Any untreated surfaces tomorrow might be a bit slippery.

Tomorrow is a transition day but we really tap into the warm surge of air on Wednesday. Highs around the area will be in the mid to upper 50's!

Active Week Ahead

Last winter, our problem was warmth. This winter, while warm at times, I think most of you would agree that cold air hasn't been an issue! I mean, we are going on 100 hours now of our temperatures being below 32 degrees. Even for New England, that is a long cold outbreak!

But as we know in the weather world,changes are ahead. Not for tonight however. Take a look at the current afternoon temps in the area.

There is still plenty of cold air for everyone.In fact, some new guidance suggests that the while the rest of us see some moderation in the temperature department over the next few days, northern New England will hang on to that Arctic air through the weekend.

As for any snow, well the fishies are going to get a good storm, but not us. Take a look one model run from this afternoon.

We see here that the energy diving from the mid-west eventually develops into a decent storm, just too far offshore. We have seen this happen with our last 3 potential storms. There is not one exact cause for why this is happening, but one definite reason is the strength this pool of cold air has. Just look at how dry and cold the air mass is above our heads.

This weekend, the dry and cold air wins out, giving us a shot at some snow showers tonight but thats all. We went 0 for 3 this week. That is starting to look like Paul Pierces first quarter scoring line.

Next week looks like an active weather pattern. The cold ail will back off a bit and give way to a warm up by mid week. By Wednesday and Thursday, we should see temps in the mid 40's.  Wednesdays high temps are shown below.

But this comes with a price. Two storms will make a run at us as our boundary between warm and cold air becomes very sharp. Both will feature a whole mixed bag of precipitation types, including ice. Interior areas should be cautious of the Mon/Tues and Wed/Thur time frame. But of course, I will have more about that next week! Enjoy the weekend!

PS. I added a new polling feature to the blog. Answer the questions and win prizes! I am just kidding, there are no prizes, unless you consider a lunch date with me a prize.

A Tricky Snow Forecast

Lots to talk about, so I shall get right to the point.

A small and relatively weak storm is currently moving out of the Great Lakes region.  This system will slide to our south rather inconspicuously until reaching coast, transferring its energy (as these storms so often do) to a new, stronger storm center over the ocean.

Under normal circumstances, this coastal storms track would be too far east to really give SNE any significant precipitation. But a few ideal atmospheric conditions have set up for accumulating snowfall and even heavy snowfall bands in some areas.

1.) Cold air. Shortly after the Patriots waxing, some real cold air settled in over New England. Most areas are currently in the mid to low 20's, even in Cape Cod and the Islands. What this means is any moisture that does fall will be snow. It also means that the snow will be light and have a high "fluff" factor. Normally, the snow to rain ratio is 10 to 1 (1 inch of rain equals 10 inches of snow). The ratio will be closer to 20 to 1 tonight, meaning snow can pile up higher with less moisture.

2.) Atmosphere Instability. I will try to avoid too much technical stuff here. First, a physics review.  Atmospheric instability is created when warm air at the surface rises uninhibited through a cold pool of air just above the surface. This phenomenon is commonly seen in those high and towering thunder clouds we see in the summer. The approaching storm will in a sense "kick-start" the comparatively warm air we have at the surface upwards, rising swiftly through the cold air and creating more clouds and enhanced precipitation. The areas of heavy precipitation can become localized along a trough (line) in a sort of inverted manner, like a tail hanging off the main storm. This phenomenon actual has a name, Norlun trough, named after the two meteorologists who first observed the pattern. With these troughs, its all about location. Where does the tail set up! The bands of heavy precipitation are quite narrow and don't move, resulting in high snowfall variability and a big bust potential in snowfall forecasts.

Alright, you hung with me through the boring stuff, so now to what everyone wants to know. How much? Since I can't make my own maps due to a lack of talent, I chose to borrow this map from NECN meteorologist Matt Noyes.

A couple of things to note. The snow won't really start to accumulate until around midnight. The heaviest snowfall will occur overnight, with most areas picking up a fluffy 2-4 inches. Not enough to cancel school I'm afraid. Some heavy snow bands will set up along the Norlun trough, which figures to be stationed over the outer Cape, Cape Ann and Portland, ME. It is here where some areas may hit the jackpot and a foot of snow. Unfortunately, we won't know where until the storm develops.

Its worth noting that this is a type of scenario where one town may get 2 inches of snow while the next town over gets 8 inches. Quite variable and hard to predict. Not that I would expect any sympathy from you good people. Some people will wake up tomorrow disappointed, while others might be pleasantly surprised.


Here are two interesting further readings on Norlun troughs. One from Matt Noyes concerning the last Norlun trough we had in 2011 and the other the summary of that last storm from the NWS.

Matt Noyes
NWS

Nor'easter makes a very close pass tonight

Those of us who love snow storms are getting pretty frustrated. Last winter, we suffered from a lack of cold air which resulted in record low snowfall totals. This year, we finally have the cold air but we are missing the moisture!

Over the next few days, a series of cold fronts will usher in some truly Arctic air in New England. The first such front will pass through tonight, dropping most of us into the teens tonight. At the same time, a relatively strong ocean storm will pass just to the south. Some models are hinting at light accumulation over Cape Cod, with some potential for a dusting over the south shore.

The above image shows one model's thinking on total accumulation. The further south and east you go, the more likely you will wake up to some snow on the ground. I wouldn't be surprised to see some higher totals of 4 inches on Nantucket and the outer Cape.

As always, a slight shift in the track of this storm could mean more of SNE sees snow or a complete miss all together. Regardless, I wouldn't change your Friday morning plans, which probably consists of wasting time on the internet or driving to work.

The second Arctic front arrives during the middle of the Patriots game, which could make for a very COLD finish.