Joe Lundberg

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Just Cold Enough For Snow

January 16, 2013; 10:59 AM ET

Wednesday, 11:30 a.m.

Make no mistake about it; the weather right now is wild and fascinating, and it will remain so for a while. Even in the wake of two storms passing off the East Coast, a non-stormy weather pattern will be anything but boring late this week and through the weekend as the stage is set for some brutally cold air to invade the U.S. and make deep inroads into the South and East next week.

The first 'storm' dumped several inches of snow across parts of Pennsylvania southeastern New York state, and interior southern New England overnight and this morning. That snow is still falling in Maine as of late morning, but it's largely over with elsewhere. As storms go, it was hardly a strong one. If you look at a pressure analysis map, there's a 1012mb low right now over West Virginia, and something marginally deeper pulling away from southeastern New England. That's it. Not much of a storm, but it did yield a good quarter to one-half inch of liquid in the zone where it was cold enough to snow.

And that's part of the point of my message today. The snow geese that we all know and love are drooling at the prospect of bitter cold coming next week, with the idea that the very cold means it has to snow! Well, not so fast, my friend. By and large, as I outlined in yesterday's post, once the arctic air is in, there won't be a lot of moisture to be had, so the prospects for snow are not very high in a lot of places, save for the potential for a storm in New England next Tuesday - more on that at the end of the post.

If you have been a regular reader of mine through the years, you know one of mantras happens to be that it doesn't have to be bitterly cold to snow, just cold enough. That was exactly the case in the areas mentioned above. Look at where the 850mb 0C line happened to be overnight:

In last night's case, there was a warm layer above 850mb, so that places like Harrisburg and Allentown ended up with more freezing rain than anything else. That aside, there's no evidence of arctic air anywhere around the region, yet a decent snow fell with a wimpy little wave of low pressure.

And that brings me to storm number two, the one rolling out of Texas this morning:

Let me show you a wider view of the 850mb temperature forecast for tomorrow morning off the 12z NAM model:

The real arctic air on the map is way to the north, stretching from the Midwest through the Great Lakes into New England. However, underneath that upper-level low, it will become cold enough to see rain change to snow in a lot of places as moisture gets wrapped around the surface storm. That means snow will fall on parts of Mississippi and Alabama into northern Georgia tonight and tomorrow morning before the storm moves east and the snow shuts off. While the NAM precipitation forecast seems excessive tomorrow, I do believe its telling the right story - the atmosphere will become colder top to bottom with moisture getting wrapped around the deepening surface storm. So, as the intensity of the precipitation picks up, and the upper levels cool with the approach of the upper level low, rain will go to heavy, wet snow, and there will be a good thump in the southern Appalachians that will stretch up into Virginia and at least southern Maryland. There will be some places with more than six inches of snow in the mountains of upstate South Carolina, western North Carolina, and the higher ground of western Virginia into the southeastern slopes of West Virginia. Snow could even graze southeastern New England. All from a system that initially has virtually no cold air associated with, and only grows colder with each passing hour.

Then we go into a relatively quiet weather pattern, but one that is no less exciting. I'm no fan of arctic air by any stretch of the imagination, but it does make for challenging temperature forecasts. For instance, raise your hand if you forecast rain in Minot, N.D., last night and early this morning. I knew temperatures would go up under the cover of darkness across North Dakota last night. You could see the incredibly warm chinook winds blowing across Alberta into Saskatchewan early yesterday. And it seemed a given (at least to me, anyway), that the machine-generated numbers were going to bust. So did I. It not only reached 20 in Grand Forks last night, but it actually reached 37 at one point before the cold air started coming back in from the north early this morning.

That warm surge is weakening as it is moving through southern Minnesota toward southern Wisconsin and northern Illinois, but it will still be enough with wind to send temperatures well above normal for mid-January.

Another similar surge seems likely this weekend ahead of a much stronger cold front coming into the northern Plains and Upper Midwest. The trick will be how much warming, and how much wind. The more wind, the more effective the mixing. The less wind, the less effective the mixing will be - just look at the mid-Atlantic and southern New England this past weekend for how that worked out.

As the really cold air drills south and east through the Mississippi Valley and Midwest into the Lakes and Ohio Valley next week, there is the possibility of low pressure coming through the Lakes to be impacted by a southern branch feature. If the two come together in the right way, it could mean a very intense storm developing around the Northeast. The models are all over the place with it, but here's the Canadian forecast for Tuesday:

It may not come together like that, but there is still a real possibility of that impacting New York and New England ahead of the real arctic press. I'll keep tabs on that between now and then. In the meantime, I'll keep repeating my mantra - it doesn't have to be bitterly cold to get snow, just cold enough.

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

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About This Blog

Joe Lundberg
Joe Lundberg, a veteran AccuWeather.com forecaster and meteorologist, covers both short and long-term U.S. weather on this blog.