The Question of Snow

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The answer is simple if you’re in New England tonight, but it’s not so easy in Alabama or Tennessee down the road. A nor’easter working up the East Coast could dump as much as 24 to 40 inches of snow tonight and Saturday in Massachusetts north through southern Maine. This is the latest warning advisory map for the NWS in Taunton, Massachusetts (that’s the Boston office):

NWS Advisories from Taunton (Boston), Mass.

NWS Advisories from Taunton (Boston), Mass.

This monster storm system whipping up hurricane force winds along the coast and dumping feet of snow will strengthen a north-northeast wind coming from a dry, cool air mass just north of the Tennessee Valley on Saturday. That translates to a sunny, mild afternoon that feels a little cool if you’re out in the breeze. A strong area of high pressure just west of the nor’easter blocks the stormy weather west of us for a day:

Alabama and Tennessee are in just the right place for a nice, mild Saturday with a northeast wind.

Alabama and Tennessee are in just the right place for a nice, mild Saturday with a northeast wind.

What happens after Saturday starts to get interesting for the rest of our extended forecast period as well as the rest of the month to be honest.

Time nor space here on the blog allow for me to show you every map that backs up a cold/snow threats for the South and specifically the Tennessee Valley over the next few weeks, but here are some of the basic ideas we are looking at right now:

Sunday to Tuesday: Rain is the big weather story. Some cold air will move in behind the first batch of wet weather on Monday, but it will not get cold enough for a winter weather worry. Some of us may have to deal with flooding; up to 5 or 6 inches of rain are possible on the high end, but most of us will be in the 2-3 inch range between Sunday and Tuesday.

Wednesday: This is the first chance of wintry precipitation over the next 2 weeks. It looks minor at best, and will probably be a non-event for North Alabama and Southern Tennessee; however, snow rarely shows it’s hand more than 48 hours in advance (sometimes not even 12 hours in advance)! That means we will keep an eye on it and adjust accordingly. Right now, all you should expect in our little corner of the Tennessee Valley is some light to moderate rain Wednesday with a chance of it turning over to some mixture or light snow as it ends. Temperatures will be above freezing, so whatever falls will have the same impact as rain for us.

Here’s the GFS output for snow accumulation through 6 AM Wednesday morning; it indicates a tiny, tiny amount of snow coming east from Oklahoma toward Middle Tennessee. On a scale of 1-10 (1 being “spitting snow” and 10 being the nor’easter impacting New England), this would be around a 1 or 2 – not a big deal. We’ll be watching for any surprises! Just FYI, the Canadian model is much more aggressive with snow, but the European look is practically snow-less. Like I said, adjustments may be necessary as this system “shows it’s hand.”

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Beyond Wednesday and the Seven Day Forecast: A wise man (Dr. Charles Wax) once said “anything past three days is magic” when referring to a weather forecast. I like to think we’ve gotten a little better with the over-all pattern since he formed that opinion in the 80s and 90s, but he’s right when it comes to local specifics. That’s why when you see a map like this one for next Saturday night, you should understand the uncertainty involved:

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On the left, you see the “operational run,” and on the right the “ensemble spaghetti plot.” See how a lot of those blue lines on the spaghetti plot mirror the pattern in the operational run? That’s pretty good confidence that (1) it will get much colder and (2) there could be a chance of wintry weather in the Deep South and Tennessee Valley next weekend.

So what are the odds? Historically, this is the kind of set-up you’d look for if you’re going to find heavy snow that lasts a few days on the ground in Mississippi, Tennessee, Alabama and Georgia – especially the I-20/59 corridors. Is it likely? Not yet…

Dr. Wax’s words always come to mind when looking at things like this. It’s a possibility, but anyone that tells you that it definitely will or won’t happen is practicing something other than science. We’ll keep you posted!

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