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    Frank Strait

    The Next Two Storms

    12/21/2012, 6:46:29 PM

    I arrived back here in town after four days away with a blizzard in the Plains and a developing tummy trouble that kept me from posting anything until today. With a week having passed since the last time I could post anything, it's just time to pick up the pieces now. This storm was quite a doozy out there in the Plains and around the Great Lakes and the snow is still piling up tonight in some places up north. The northwesterly flow snow down the spine of the Appalachians is starting to wind down but flakes were in the air all the way into North Georgia. Welcome to winter, y'all!

    Now that I'm back and the weather has my full attention again ... well, there's a big dome of high pressure centered right over coastal Texas, so things are quiet west of the Mississippi. Our departing storm is still causing some gusty winds farther east, though, and there's much colder air blasting way to the south, all the way through Florida now. It's certainly a far cry from what most of December has been like so far, all of the South has been well above normal, the biggest departures from normal are in parts of Arkansas, Western Tennessee and western Kentucky, more than 10 degrees month-to-date, which is a pretty big deal.

    The rest of the month looks different, though. The weather pattern is changing quite a bit with the storm that's moving through now and it's much more favorable for cold over the eastern part of the country, especially closer to the East Coast. While there might be one or two mild days in the mix, especially back in Texas, we should whittle a good bit away from those departures from normal for the remainder of the month.

    The arrival of cold also means the arrival of some chances for snow over the rest of the month. Of course, parts of the area saw some flakes flying today, several inches in the higher ground of Appalachians, and we appear to have at least two more good chances for snow in a part of the South now through the end of the year.

    It looks as though after a couple of chilly days, warmer air will return ahead of the next storm we have to deal with, so snow changes are not too good with this next storm, at least in the South. It's a different story up north; I might see some snow in my neck of the woods with this next storm that will cross my area Christmas Eve night, giving me a white Christmas (that I don't want, y'all can have it but none of us have a choice in the matter). The storm in question is off the West Coast now and will arrive in the southern Plains states on Sunday. At the same time, moisture will start to surge northward into the Southeast ahead of the storm. I don't expect to see much rain from it through the day Sunday but a few showers might start to pop up in the afternoon from Southeast Texas to the Tennessee Valley. The storm should get going that night with rain and thunderstorms blossoming over the Mississippi Valley. Y'all are probably wondering if I'm concerned that there might be severe storms, since there was a good bit of severe weather from the now-departing storm system and I am worried that we will see some severe weather on Monday across the Gulf Coast from Louisiana to the Florida Panhandle. Yes, weather geeks, I am leaning on the slower European model solution. But, even if the GFS is right there's a chance for severe storms right along the coast. By the end of the day Christmas Eve, the rain should be in Virginia and the western Carolinas, and covering a good bit of Georgia. It will push offshore that night with colder air settling back in behind it. It appears that some flurries could be around at least into West Virginia behind the storm that night.

    Hot on the heels of this storm will be another bigger and stronger one. There are differences between the models on the details, but it looks as though there will be snow on the cold side of it and more nasty thunderstorms on the warm side of it. It will also be a challenging storm to forecast for thanks to what we weather weenies call a "Miller B" storm setup ... that means the storm center will look like it will be cutting up west of the mountains but will then jump to the East Coast at some point. (This is opposed to the Miller A setup, where the low either rides along or near the Gulf Coast and then rides up the East Coast ... easier to forecast, often stronger, and more likely to cause snow in the Southeast.)

    If you believe what the European model is showing ... and I think it's got a good chance to be right ... a stripe of snow will begin in the Red River Valley with this storm on Christmas Day and then really go to town in Arkansas as the storm really starts winding up farther south that night. The model shows the stripe turning northeastward from there as the storm winds up and tracks toward Crossville, Tennessee before starting the jump to the coast. The model has a fairly big stripe of 6 inches or more starting in southeastern Arkansas and a lot West Tennessee and a good chunk of Kentucky getting a foot. Farther east, it's a lot of rain, but after the low jumps to the coast and with another round of northwesterly flow snow behind the storm, several inches could hit West Virginia and western Virginia.

    I don't want to even think about how much snow the model says I'll get up here. I might need a yardstick. It feels like the tummy bug is coming back now ...

    Actually, the GFS doesn't handle the storm all that much differently, it just has the stripe of snow farther north, from Amarillo to Oklahoma City, to Northwest Arkansas to the Ohio Valley ... and doesn't show as much snow falling.

    No matter which storm is right, I think we're in for a second round of severe thunderstorms close to the Gulf Coast. This may start in Southeast Texas late Christmas Eve night and head east Christmas Day. It's probably only a question of how far north the severe storms can get. This time of year, it's most likely only within 50 miles of the Gulf Coast. However, with a storm as intense as this one is likely to be, severe storms farther north, perhaps up to I-20, is a potential concern.

    The problem with these "Miller B" storms is that cold air tends to get trapped, "wedged in" as we say, east of the Appalachians and gives you the potential for snow or ice there. In December, it's not usually a problem all the way into Carolinas, but this will be a concern for Virginia and Maryland, especially the Shenandoah Valley. This far out, though, the devil is in the details. This would probably be Wednesday, "Boxing Day" as they call it in Canada, the U. K. and other places, when this would hit.

    The differences between the models are not big on this storm, but as I said, I am leaning toward the Euro on this one. First, it looks a bit farther south, which I like because I think the NAO will not jump to positive the way the GFS is showing next week (translation: a blocking high should stay in place over Atlantic Canada or Greenland). Second, it looks like the PNA is going positive (translation: it looks as though there will be a ridge close to the West Coast), which is typically is a better setup for snow in the Southeast. Actually ... if the NAO stays strongly enough negative and the PNA gets as positive as the GFS is showing ... even the Euro may not be far enough south and we would be looking at more of a "Miller A" setup instead. That should perk up the eyes of Carolina snow lovers that dig the jive I'm speaking here, as that would mean more of a "Gulf low" sort of setup ... see the 12Z Friday run of the Canadian for an illustration. Maybe it's not cold enough for any real snow outside the mountains and foothills even if the Canadian is on to something, but I know there are some giddy snow geese right about now.

    If this were not enough ... another storm could cause some snow at least as far south as I-40 next weekend. And maybe a few more severe storms along the Gulf Coast, too.

    I told y'all the weather was gonna get busier, and more fun for those that like snow!

    Historical Note: Those of you who are weather weenies ought to know who this Miller guy was. Back in 1946, a weather researcher named James Miller from New York University wrote a research paper called "Cyclogenesis in the Atlantic Coastal Region of the United States" (PDF of his paper), in which he discovered that East Coast storms follow two patterns. One is Type A where the low is well defined and tracks across the Southeast or Gulf of Mexico, then close to the East Coast and the other is Type B, where the storm center is not as well defined and often there is more than one, usually becoming consolidated near the East Coast as the storm intensifies on its way northeastward.

    The views expressed are those of the author and not necessarily those of AccuWeather, Inc. or AccuWeather.com


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