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Joe Lundberg's Weather Blog

A Different Kind of Cold

Jan 27, 2012; 10:49 AM ET

Friday, 11:10 a.m.

And no, I'm not referring to my head and chest cold that is now at day 10 in residence in my body. It's a cold that has been more tenacious and more debilitating than any illness I have ever suffered through. I cannot wait to get it behind me so I can get out and enjoy some of the mild weather that is occurring and will occur.

I'm instead referring to the different kinds of cold air masses we see in the course of the winter season. A week ago, a true Arctic air mass moved through the pattern, one that dropped temperatures below zero across portions of upstate New York and northern New England, including a 23 below zero chill Sunday morning in Caribou, Maine.

That type of air mass is actually colder in the low levels than it is aloft, a stable air mass that is almost always found with large high pressure systems. With a clear sky and light winds associated with the presence of the high, you promote ideal radiational cooling conditions at night, which can be enhanced with snowcover (especially a fresh one), the freshness of the air mass on the scene and any natural collection places in the local terrain to enhance the draining of the coldest air into low places.

If you look at the 1000-500mb thickness being forecast this weekend across the Ohio Valley into the mid-Atlantic and Northeast, you'd think some similar temperatures are to be expected. Here's a close-up look at the 12z Friday NAM forecast for Sunday morning:

Yet the forecast highs are marginally below normal for a couple of days. The difference is that the cold is more centered aloft than it is in the low levels. That's a more unstable kind of cold, one that promotes some overturning of the air mass and allows you to get as much out of the air mass as possible. In other words, the low levels will be about as warm as you can get given the amount of cold aloft.

In the spring, this often leads to temperature forecast busts by being consistently too cold on the forecast, especially if there's plenty of sunshine and any kind of wind. For now, it's still the dead of winter, so that kind of dissipation of the instability via sunshine and wind is not nearly as effective.

And that leads me to the forecast a week to 10 days or so from now, when another fairly strong, upper-level trough dives into the East. Sure, it looks impressive:

However, the cold air is most likely to be stronger aloft than at the surface, and the source region is hardly going to be cold. It would seem that despite the 'cold' look to the upper pattern, when it all comes out in the wash, it probably won't be very cold air all. Now, if that same pattern had a 1040mb high bearing down on the Midwest and Great Lakes, I would guarantee you a stretch of below-normal cold for at least two and probably three days over a fairly large area, but I don't see that happening.

Time for more hot tea. Maybe with lemon and/or honey. And some chili. And more rest.

The good news is that a week from now, we'll already 'know' if there are six more weeks of winter, or of spring is just around the corner!

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

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