Life is all about timing and so too can that saying be applied to the weather Wednesday. By about 5 AM snow is going to overspread the area even in Boston. This means for the commute anywhere from a coating to 2 inches will have fallen, depending on where you are located. Since the storm is coming up from the south, areas over interior Bristol and Plymouth counties should have the most on the ground during the morning. Let's call it now, a horrible commute Wednesday is in store. I am also expecting many schools to stay open adding to the traffic. Since we aren't getting a major storm and there will only be a few inches of snow during the day, schools and businesses should stay on a regular schedule. However, as you know, the tolerance for bad weather has declined exponentially in recent years and it seems like some towns are close to calling off school for flurries. I feel old lamenting about school not being called unless we woke up to half a foot of snow and the same was expected during the day. I'll save that rant for another blog. Follow me and my forecast during this storm and others on Twitter at @growingwisdom
Tomorrow is going to be all about the temperature. Along the coast the precipitation will start as snow, change to some rain and then back to snow before ending. This will make for a very difficult forecast of accumulation. This map shows the surface temperature pattern as predicted tomorrow. You can tell by the colors that it's too warm to snow over Cape Cod, but cold enough for snow in Boston, at least to start. The exact thermal profile of the atmosphere will have to be evaluated throughout the morning. In other words, just like the last storm, a few miles will make all the difference in what you see at your house. I expect the rain-snow line to try move inland early in the morning but how far it gets we don't know yet. I am confident it will be snowing in many places, including metro Boston, in the morning and the radar prediction clearly shows the entire area covered with something. The radar only predicts that precipitation will fall, we have to determine the type. It will be cold enough for several hours of snow in the Route 495 area and even east to Route 128. Boston, Lynn, Rockport and south to Quincy and Plymouth you are in the zone where it will snow, then rain, then end as a bit of snow or drizzle. Lawrence, Fitchburg, Natick and Milford you should be all snow with areas in central Worcester county seeing the highest amounts of 4-6 inches of snow.
As mentioned, the rain-snow line will be tricky to forecast. This means the amount of snow will increase as you move west. The distance between who gets 5 inches and who gets an inch won't be more than 20 miles in some cases. The gradient of accumulation can shift west or east depending on how the system evolves. Right now I expect Boston to see up to an inch or two of wet snow but those amounts will increase quickly as you move west and north.
The reason we can't tell temperature gradient more specifically is that the computer models don't yet have the ability to see small scale features much under 10 miles. Think of it this way, I can take a picture of you with my camera and see your face, I can't, without a special lens or zooming, see your eyelashes. The models can see the warm air at the coast and the cold air inland, but we just can't resolve the few miles between the two very clearly. I expect this to change in the coming years as computer power increases.
Another blast of cold air will be headed for New England Sunday. The timing of the arrival of this air is not definite so it may be that we are just chilly for the game and not windy with low wind chills. Give me a few more days to evaluate the weather for the game. First thinking is that temperatures will be falling during the game with a gusty wind.
Overall pattern shift
As usual, winter has not been affecting the country evenly. For the past week, the west and the southwest have been significantly colder than normal. From San Francisco to Tuscon, Arizona frost and freeze warnings are up and farmers are concerned about damage to their crops. In the east, from Florida to Maine, temperatures were running up to 20F degrees warmer than you would expect in the middle of January and much of the snow has melted. Now, we are watching the pattern slowly undergo a change which is bringing some colder air east of the Mississippi and into New England. The big question is, just how cold will it become next week?
Let's do a quick lesson in meteorology. I want to talk about how warming high above the earth can actually create cooling down here where we live. To understand this phenomena you have to remember the atmosphere is like a layer cake. The layer closest to the ground is called the troposphere and is where most of our weather occurs. Just above that is the tropopause and that is the dividing layer before you get to the stratosphere, the next layer up. The stratosphere is also where the ozone is located. The ozone keeps that layer somewhat warmer than it would be without ozone as the ozone traps some of the sun's ultraviolet light from reaching the earth below. Even with this warming, it is still very cold at 50-80 below zero! Another aspect of the stratosphere is that there is a whirlpool of spinning air up there called the polar vortex. This vortex is also three dimensional and extends to the ground. While temperatures in the stratosphere are very cold, sometimes, in a matter of days, temperatures can suddenly spike and become warmer. Now, warmer up there might mean going from 80 below zero to a balmy 35 below zero, but that increase is dramatic and significant. This phenomena is known as sudden stratospheric warming (SSW). This warming can change the way the winds blow in the stratosphere and create changes in the troposphere below.
One way these change manifest themselves is by bending the jet stream beneath the warming. These changes can also affect ocean currents, ice flow and water temperatures. The jet stream will buckle and allow the cold air over the arctic to spill south. One problem is that it is difficult to forecast the exact location of the buckling wave and thus the eventual penetration of the cold air south. These SSW events, when they happen, produce a cooling somewhere at the surface about 75% of the time. Another problem is that our computer models have a difficult time with this phenomena and the accuracy in forecasting the extent and intensity of the resulting cold isn't as good as the general day to day forecasts. The last SSW event, a couple of week ago, most likely helped create the recent extreme cold over parts of the United Kingdom and the cold across the southwest United States.
End of January
There are still indications of more blasts of arctic air entering the United States throughout January. Later next week another round of SSW is predicted. You can see this prediction on the image below. The result may or may not be additional blasts of cold arctic air which end up on this side of the world or perhaps affect parts of Europe or Asia. More on this in the coming days.
Gardening this week
I have a new video to show you this week on moving a tree. You might think big deal, right? However, the tree that got moved was done so without hurting any roots. They used something called an air tool to blow the dirt away and then lift the tree to its new home. Check it out.
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