It won't be long now

I can see it... I can feel the beginnings of it... I am dreading it!!!! The Arctic Blast or Life In The Freezer or whatever other catchy names the national media come up with... well it's knocking on your door! By the way... my favorite is Arctic Blast because it's true!

I was glad to see daytime highs actually climb into the 40s out in southern Kentucky on Wednesday afternoon. Though wind chill readings took some of the heat out of the air. (Really... 40 isn't warm... but it will feel like a heat wave compared to Thursday-Friday)

You may not believe I am saying this... but after all this talk about super cold temps... well I am ready for SPRING!!! I can't believe I said it either. I love the snow and 30 degrees, but 2 above zero?!?!? Come on Mother Nature give us a break here. OK Now that my break-down is over how about we address the real situation at hand.

It's quite simple you see... The low that swings through here during the early morning hours on Thursday will bring us some mind numbing cold temperatures. Highs are going to have a hard time hitting the 20 degree mark. Though some locations will probably do just that... most will stay in the upper teens. You factor in the howling winds that will be present with the passage of the system and you've got single digit wind chill readings.

Now for the strong northwest flow that will follow the clipper into Kentucky. It's the source for the colder air and it will also be the trigger for numerous snow showers sticking around on Thursday. There could be some spotty accumulations of up to an inch or less in most locations. The snow shouldn't have any trouble sticking to anything with the cold surface conditions that will be present. The wind will just keep it moving around!

Once the winds calm down and the skies begin to clear on Friday morning... we'll then see the truly cold stuff finally settle into eastern Kentucky. I have stuck with this same number all week and I don't think I'll change it now... so lows that morning will be near 2 above zero. Just with the slightest little breeze temps could be knocked below zero at any given moment. Friday's winds will not be anything like Thursday's so a significant wind chill isn't anticipated. The cold air will come and it will pack a punch and a half. There is enough snow on the ground to our north to keep this airmass chilled. One of the factors you consider with cold or warm air advection is how will the surface change the airmass as it moves over the land. In this case it is just keeping most of the cold packed right there inside the heart of this blast!

WRF Friday Morning

GFS Friday Morning

These two look very similar! A good feeling this late in the game!

Now time to comment further on my "Too Cold To Snow" thought that I mentioned in my last post. This could be a very technical discussion, but I will try and keep it simple. The answer to the question of can it be "Too Cold To Snow " is NO , it can’t be too cold to snow, but is gets increasingly difficult the colder it gets.

First, an important concept. Warm air can contain more water vapor than colder air. That is to say, there is more water vapor present for producing precipitation in warm air than in cold air. When any air mass reaches the point where it can’t contain any more vapor, it becomes saturated (also called the dew point). When the dew point is reached condensation occurs, clouds form, and the more droplets that form, the greater the chance of them colliding and forming bigger drops. When they get big enough, they fall to the ground as precipitation and if the air is cold enough, they fall as snow. But when the air is really cold, it can’t absorb as much water vapor and therefore has less precipitable content for making snow.

You can see from the chart below, that as the air gets colder there is less water vapor present. The less water vapor in the air, the less precipitation that can be produced. When it is 32 degrees there is a lot more water vapor present than at 0 degrees so a lot of snow can be produced and the snowflakes are usually bigger. When the air gets really cold, there really isn’t enough water vapor in the air to get a whole lot of precipitable accumulations in a short amount of time and the snowflakes decrease in size. Therefore, as it gets colder it takes much longer for there snow to accumulate on the ground. And when it’s really cold, say below -40 very little precipitation can be produced. Ice crystals can form, but they are extremely small.

Stay warm and stay inside if at all possible!

C-Ya Bye

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