Winter Wx Update (Issued 9:00pm Tues)

Believe it or not, this storm is more complicated than the last one. Now, we have this very bitter cold arctic airmass in place. On top of that, our neighbors to the west have significant ice, which makes it hard to warm up. Will the incoming warmer air be able to push the colder air north like last time? If so, will it make it as far north as it did last time? I’m becoming convinced that the answer to both questions is “no”.

The good news is that models have trended drier with this storm. Therefore, even if we do get all ice or all snow, amounts should be lighter than they would have been from this last storm. Never the less, accumulations would be enough to cause serious disruptions to travel and possible damage to trees and powerlines.

I should emphasize that forecaster confidence, whether it be me, the NWS, or whoever you watch on TV, is very low. I speak for us all. (ha)

I have updated my timeline. I have edited out the change to plain rain during the night Wednesday. I’m no longer convinced that changeover will occur during the night. This last storm came during the day and the heat of the afternoon, in part, helped many of us out. Much of the precip from this next storm will come in the night and morning, when we tend to be colder.

Please note that times may change by as much as a couple of hours either side of the guidelines. And please note that colder spots of the plateau could see a longer duration of wintry precip. I do think the onset for many of us will come later in the afternoon, though confidence is too low to say for sure.

NOTE: If you live south of Interstate 40 you have a better chance of warming up. If you live north of I-40 you have less of a chance of warming up. (Remember, Crossville Wal-Mart is south of I-40, for reference).

Worst Case Scenario:

Scenario #1: Dominant precip type is freezing rain and we get up to one half inch of ice. Ice storm criteria is met at 1/4 inch of ice. Probability of this happening at about 20%.

Scenario #2: The precip stays mostly snow and we get 3-6 inches of snow. Probability of this happening is about 30%. (Probability of this happening for northern Fentress and Overton Counties at about 50%)

Best Case Scenario:

Scenario #1: We warm up rapidly, even during the night Wednesday, and much of the precip falls as cold rain. Probability of this happening is at about 20%. (Chances for this happening north of Cumberland County are about 10%).

Scenario #2: Sleet mixes in at all times, significantly reducing accumulation of ice and/or snow. Probability of this happening at about 30%.

To Conclude:

I sure hope this helps you out. I will, of course, have a big blog update in the morning. Just do what we always do and prepare for the worst, while hoping for the best.

Today, we had some nice snow flurries and snow showers. Arctic air is very cold and very dry. Cold air can’t hold moisture very well and is forced to squeeze out any moisture that it comes into contact with. Like today, sometimes that moisture is squeezed out as snow flakes. During bitter cold times, especially in the arctic, the cold air sometimes squeezes out the moisture in the air even if there are no clouds! You’ve probably seen that happen here during times of sub-zero temps. The air just glitters with the tiny snow flakes. We call that “diamond dust”. So, it can snow without clouds sometimes! How neat is that? Air need not have clouds to have the moisture condensed out of it. It’s kinda like dew in the mornings, too. That moisture is condensed out without clouds dropping the moisture. It’s kinda neat when you think of it.

If it makes ya feel any better, we should be in the lower 50s by Tuesday! That’ll feel nice!

See you all in the morning!

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2 thoughts on “Winter Wx Update (Issued 9:00pm Tues)

  1. Excellent wx report mark. I especially like the discussion about confidence levels and confidence by area. Bigfoot would be proud!

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