Weekend snowstorm! 12/13/13
Hi folks. Just had a chance to review the latest computer models, and I wanted to update everyone with the impending winter storm coming for this weekend.
Well… here we go! After reviewing the latest data, it now appears as if a significant, albeit fast moving winter storm/nor’easter will impact much of central and eastern New England starting by mid-afternoon tomorrow. Although not one of our biggest storms that we have seen, will be siginificant in its own right. The fact that this is happening, still in the first half of December, is noteworthy.
If this trend were to continue, which I am fairly confident it will, we can expect even larger storms beginning sometime after Christmas and heading well into January. As my winter forecast pointed out, this may turn into a wicked old fashioned winter, with heavy snows, followed by bitter cold weather. I’m getting ahead of myself!
So let’s get into the details. Our storm is now developing as an area of moisture in the south central states associated with the sub-tropical jet stream. At the same time, energy from the northern jet stream is diving southeast towards the mid-atlantic region. While not actively phasing together, the interaction between the two will spawn a new low pressure area somewhere near New Jersey. While all of this is happening, a strong area of high pressure is building north of New England, supplying us with fresh cold air.
This is critical. Not only will it supply us with cold air, but it will also act as a block, forcing the storm to pass east of Cape Cod and Boston. As this is happening, the storm will rapidly intensify, sending a plume of heavy moisture up into eastern Massachusetts, southeast N.H., and most of Maine. With the cold air banked up to our north, alot of this moisture will be falling as heavy snow. Most computer models are painting 1 to 1.25″ of liquid precipitation. As a rule of thumb, 1″ of liquid equates to about 10″ of snow.
Many other factors come into play that can change this equation. If the air is colder, and the snow is dryer, a term called the “fluff factor” can actually accumulate the snow much higher, sometimes even double the amount! However, if it’s a wetter snow, or any mixing occurs with rain or sleet, these amounts can diminish to even half this amount. As you can see, it can become a tricky business predicting forecast snow amounts!
If this falls as all snow where you live, you can expect anywhere from 8 to 12″ of snow to fall. Now, because many of us live right next to the ocean, there may be some complications, which I will explain in my forecast. Fortunately, it will be a fairly fast moving storm, as we don’t have a Greenland Block in the negative phase to slow the storm down. Had it been in the negative phase, we could of been looking at a storm with the same type of intensity as the blizzard of last February!
Now for your storm forecast! Look for some increasing high clouds to overspread the area tonight. With the waxing moon, you may get a chance to see a halo around the moon later! It will be very cold, with lows mainly in the teens. Watch for lowering and thickening clouds tomorrow. It will look like snow is on the way, and sure enough, watch for some light now and flurries to begin falling sometime after noon. It will remain cold with highs mainly in the 20’s. Watch for the snow to pick up in intensty after dark tomorrow, and roads to become slippery. Winds will also begin to increase from the east northeast. As we head towards midnight, heavy snow will begin to overspread much of the Greater Boston area along with a gusty wind at times from the east northeast. From about midnight tomorrow night until approx. 8:00 am Sunday, snow rates may reach 1 to 2 inches per hour. At this rate, we can expect a general 8 to 12″ of snow to have fallen by the time the storm ends.
Now for the tricky part. With it still being early in the season, the ocean temperatures are still a bit on the warm side. If the storm passes close to the Cape, winds may veer in more of an easterly direction right along the coast including Boston. This may briefly warm up the temperatures to slightly above the freezing mark and mix the snow with sleet or rain for a time. So if you live within 5 miles of the ocean in eastern Massachusetts, amounts may be cut back a bit, say in the 6″ to 8″ range. If you live further away from the ocean in the West Roxbury, Newton, Needham areas, amounts should increase to 8 to 10″. Same holds true just north of Boston in the towns of Melrose, Medford and Woburn, where a good 10 to 12″ should fall. Further inland to the north and west of Rt 128 from Worcester, up to Nashua N.H. , up to Portland, Maine, amounts should increase to 10 to 14″. Further in the interior of New Hampshire and up in ski country, less precipitation may fall, however it will be colder, so you too can expect anywhere between 6 and 12″ of snow!
If you live south of Boston, this is another tricky call. Look for a burst of snow on the Cape with a quick 2 to 4″ accumulating before it turns to rain. As you travel off the Cape into interior southeastern Massachusetts, this is where the heaviest precipitation will fall from the storm, but there will be temperature boundary issues in the atmosphere. From a line from Providence, to Taunton over to Plymouth, you can expect a solid 3 to 6″ of snow to fall before it mixes with sleet and freezing rain, possibly changing to all rain as you head over to Plymouth, Scituate and Hull areas. This will keep accumulations down, and make for a sloppy mess. The further north you travel from there, from Easton to Brockton and Randolph areas, snow accumulations will increase rapidly, ranging from 5 to 10″ with less mixing.
Well that’s about it for now! Stay tuned for updates as there will always be some surprises with storms like this! Keep safe, and I will see everyone at my usual post time on Monday morning! This is my current thinking. If there are any major changes, I will update this blog on Twitter and Facebook.
~Thanks for reading!~
Pete