Friday, January 11, 2008

All hail the pattern change

Very good news for winter weather lovers in the medium and long range -- all signs point to a major pattern change with sustained cold and a much higher chance of storms.

Almost all models point to a major cold outbreak across most of the central and eastern U.S. starting late next week into next weekend.

It all gets started in the Wed. night/early Thursday timeframe. As cold air begins to seep southward from the arctic regions, low pressure forms in the Gulf of Mexico. Will cold air arrive in time to make this a winter event? Way too soon to tell. Here is the storm depicted on the just-finished 12z GFS run.

More cold is ushered in the wake of this system, then another low tries to crank up in the Gulf. By the following week, cold is entrenched over the U.S.

One reason is the emergence of what pro mets call "blocking" over the Greenland area. This blocking "locks in" a cold pattern. If you've noticed, we've had what is called a "progressive" pattern thus far this winter -- it gets cold and warm, but nothing lasts very long.

With blocking, which can be measured by the North Atlantic Oscillation, cold air is continuously funneled south for weeks at a time, meaning one part of the N.C. snow equation is basically set -- then, all we need is lower pressure for a nice snow.

Check out this long-range map from the 6z GFS run. It's plenty cold here for snow, but notice the bitter cold on our doorstep -- this is all "fresh" cold, not the old stale airmasses out of which we have been hoping to squeeze a snowstorm.

Bottom line: GREAT pattern emerging -- first chance at a payoff is Wed. night/Thursday morning, with good shots every few days thereafter for the next couple of weeks.

BOLD PREDICTION: We will see accumulating snows in Cleveland County before the end of January!

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