Someone stacked the deck...

Here in Carroll County anyways.  Last weekend a clipper dropped 5" of snow.  This past weekend, a cold front supposed to be all rain, dropped around 1-3" of snow depending on your elevation.  What's so good about this you ask?  These two snows, both within a week of each other, in a La Nina winter, are very very rare exceptions.  We usually don't see accumulation of snow out of a clipper, and very very rarely, do we see a cold front come through, with just mainly snow.  Blame it on the cold air.  It has felt like February for the first half of the month, and the pattern shows no signs of letting up until after Christmas. 

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The gun is loaded:

Let me try to explain this to you in simple terms.  Earlier this winter, we were seeing storm systems slam into British Columbia, and the Pacific Northwest.  It is an old saying that wherever a storm enters on the west coast, it will leave at that lattitude on the East Coast.  While we haven't seen a single Nor-Easter yet this year, we haven't had a storm dig far enough south in the Jet stream to do this.  This was the pattern til about the first of December.  However, each time a storm would run this way, the cold air, (The cold air is always in the trough, a trough is essential to storminess), it would push the trough further east. This is the pattern depicted in the picture above.  To the East of the cold front, the atmosphere was simply warm, with ridging going on.  Eventually though, the storminess, and a Block over Greenland, forced the Trough to set up over the Eastern US. ( Below)

Here we have the current pattern.  It is incredibly warm in the SW, with records being set all over the place in California.  While in the Eastern United States, the trough has set up, and given the coldest start to the Winter in recent memory.  The one problem, there is no southern storm track.  When this happens, it is hard to get snow in the winter months.  Our snows here in the South come from the Gulf of Mexico.  We are always on the fine line between snow and rain, warmth and cold, due to our lattitude.  However, we have seen a couple a system dive in from the NW that brought us several inches of snow.  Even Yesterday, we had a brief respite of the pattern described earlier, only the air was so cold on the front end of it, what is usually rain turned out to be snow in the Mountains.  This type of pattern is good, for cold weather but not for snow.  So now, onto how the gun is loaded.  I'm about to show you.

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We have two oppurtunities for significant winter weather over the next week.  The first will be a rather light to moderate event.  An overrunning event, that won't be a monster, but will probably cause some headaches. It's a very simple setup.  The warm air to the South will try to fight the cold air to the north.  A weak wave of low pressure will form somewhere in the Tennessee Valley, finally a Southern piece of energy, albeit weak, we will finally have a classic setup for Southern Virginia.  The problems:  It is a fast mover, and weak, and the track will be huge to if we get snow, snow and ice, ice, or rain.  Here is the setup.

Scenario One:  This is a good setup for snow in the Mid Atlantic. Ice, in the Kentucky, Tennesee Regions. Someone will get several inches.  Fine tuning where, is tough.  In the first scenario, the cold air surpresses the storm somewhat, allowing the cold air to remain along the Eastern slopes of the Appalachians, providing a significant ice storm for the Piedmont of NC and Virginia, and several inches of snow from the Mountains of North Carolina up through the entire Southern Half of Virginia. 

Scenario 2:  This is a good setup for snow over the Shenandoah into DC.  and Ice into the Southern half of Virginia, with rain over North Carolina and Kentucky.  Right now, the models are showing this scenario. 

Really, there is no difference, except the placement of the low, and how far north the warm air can intrude.  Two things: 

1. This will be a fast mover, no one should see more than 6" of snow, or .25" of ice.  I think Virginia will get the main beef from this snow.  If it sets up North or South, or right over Roanoke, is where we have to fine tune.  One thing we could have going for us is this.  The cold air is so incredibly deep, that even if the warm air does nose in, it may not matter.  We saw this last year twice.  Two "Miller B's", (storms that traditionally bring warm air and rain), rode to the west of us, however the cold air was so deep and hard to dislodge is ended up snowing with ice at the end.  This could happen again, time will tell.  Right now, my early early call is 2-4" of snow followed by a layer of ice. 
2. This storm sets the stage for the next one.  It could very well be a good opening act, to the main show. There are some signs showing this could be a historical storm, or a no storm.  Many of the early signals are lining up with the January 1996 storm that obliterated the Mid Atlantic. Or, it could dissappoint, and the main show might not even come to the stage at all.

I will post on this storm maybe later tonight or tommorow.  It's on and off the models.  Also, if anyone is interested in joining an in depth weather discussion, check out Kevin Myatt's Blog at Roanoke.com