Weather

Monday Snowstorm Rain-Snow Line May Become An Issue

Late update
As new data is coming in, I am thinking I will be lowering totals from Boston southwest to Providence closer to 6 inches. More in the morning.

8PM Update
A few things changed in the afternoon model run, but not enough for me to move the snow bands much at all, yet.

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What I’ll be watching for tonight and early tomorrow is if a trend develops to move the warmer air further north or not. I don’t like to flip the snow amounts down only to move them back up again. I don’t see enough evidence to bring the warm air into Boston and lower totals yet.

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If tonight’s run brings the ocean air further inland, I’ll drop them tomorrow morning. There are a few models that are surging the warm air north. There is one model called the RPM, from Weather Services International that brings a lot of warm air into the system. If this is correct, the forecast will change dramatically.

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Most of the rest of the forecast is the same and you can read my thinking from earlier today below.

Morning Blog
Winter, some of us love the season, some of us hate the season and some of us feel a little bit of both. No matter how you embrace the cold and snow, you still have to move around in it. Living in a crowded place with narrow streets, lots of cars and many determined people can add lots of challenges to winter.

If we lived where it wasn’t so congested, I think all the snow that comes along with winter wouldn’t be such a big deal. I can deal with cold, because I can just add a new layer, it’s all the snow that becomes the real problem and it’s about to get worse. All this after the snowiest 5 days on record in Boston (29.7″) and Worcester 40.7″).

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Monday Snowstorm
We have another storm coming and many areas will see a foot or more of snow. Some towns will get less than that and others more. For much of the storm, temperatures are going to be very cold and this is mostly a good thing. The cold keeps the snow light and fluffy, especially from about Boston to Providence and points northwest.

Milder air will work into the south coast during the storm. I’m still unsure exactly how far north the milder air will move. I do think parts of Cape Cod and the Islands will see a mix of rain and snow during the storm and perhaps even a change to all rain, briefly.

The temperatures are critical during this storm, not so much because of snow versus rain, but because of the amount of air in the snow or fluff factor. Check out the image and chart below. Notice, the colder the air the more snow the exact same amount of moisture creates. In other words, if you melted 10 inches of snow that fell at 28F you would get about an inch. If you melted 15 inches of snow that fell at 20F you would still get an inch. Drop the temperatures even further and you could get 20 inches of snow from just an inch of water.

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The GFS is forecasting close to an inch of liquid from the upcoming storm and the European model is also in that range.

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When I put together the accumulation map, I take into account all sorts of variables including temperature. Some areas could see 15-20 inches of snow or more, if this amount of moisture does fall as snow and it’s 10F. I’m not putting that on the map just yet.

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I want to get another look at the models this afternoon and will update again this evening, but I don’t expect much change. I think generally we are looking at 10 to 16 inches of snow in a large swath, with less across the south coast and Cape Cod/Islands where the snow will be wetter or even mixed with rain.

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Those numbers are large, but if you do get a foot of snow in these very cold temperatures it will be super easy to move around and settle to about 60% of the total in 24 hours.

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Timing Of The Storm
Low pressure moves south of New England Monday and brings more snow to the region. The storm will move into the Gulf of Maine Monday night and onto Nova Scotia from there.

Snow begins after 2AM Monday and continues throughout the day. I think it winds down early evening. The first inch or two will fall before the morning commute which means if you are someone who operates the plows, you might want to keep that in mind when watching and celebrating with adult beverages during the Super Bowl.

The map below is a predictive radar for 4AM Monday. I’ll update the timing on the storm later today here and on Twitter @growingwisdom

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Pattern Continues
A lose rule of thumb I learned when studying meteorology is winter weather patterns often lock in for about 6 weeks. They can then relock into the same pattern another 6 weeks. Think of the snowiest winters on record as having done this.

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Consider the fall and winter, we had a very cold November. This was followed by a break in December and early January. Our current cold and snowy pattern started about a week ago and will likely go well into February. To that point, there’s the chance of more snow later in the week and the long range forecast for February keeps the coldest of the cold air centered over the northeastern part of the country. Whether you love it or hate it, you might as well embrace it, because it’s not melting anytime soon.

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Map Credit
Many of the image I use come from WeatherBell Analytics. If you love weather and want to get view great maps, they are a wonderful source.

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