Christmas Post!

  Merry Christmas!

  Hopefully you've had a fantastic day. Tonight we're going to take a look at what we might have to look forward to, or not look forward to depending on your disposition, as we finish up 2017. Spoiler, there could be a lot. 

Current Conditions Across Kentucky

  Right now (10:10pmCST) there are actually light snow showers working their way eastward across western parts of the State.

Most of this is not reaching the ground since there is relatively dry air in the mid-levels of the atmosphere (the dry layers work to evaporate precip as it falls through them). It is showing up on radar a little better now though so it's possible to see light flurries throughout the next few hours. No measurable accumulation is expected either way. It is also a very cold night with temperatures generally in the mid 20's across the area. Unfortunately I think we will see even colder temps in the not too distant future. The next few days will be cold no doubt but some of the data coming in has absurdly cold air to start 2018.

Blend of forecast models showing high temps, yes HIGH temps. for the start of the year.

  A few inches of snow could also be possible should this system progress as suggested. We have been locked in a very favorable pattern for winter storms and it looks to stay that way for awhile but it takes the right storm track and so far they have stayed to our North for the most part. You all know that I don't like to pretend that I know something I don't and I certainly don't forecast based solely on model data so I'm not willing to make any detailed forecasts regarding this event just yet, and besides, there are a few days to really hammer this out anyway. At the same time, there is relative consistency with the model solutions so it's worth acknowledging (Yes, the models CAN be consistently wrong so that's something I'm considering).
    I do have above average confidence in a significant shot of cold air as we close in on New Year's though and that will be a big story going forward. I think we will be seeing single-digit temperatures at times and perhaps even colder.
 

  That's the GFS suggested "surface" temps for 28 December. It shows a very strong high-pressure over the central CONUS with a streamline of unbelievably cold air funneling into the area. If you look closely you will see that it seems to think we will see temps 20-30 degrees below 0 across the Midwest. I should point out that this is just one solution from one model at one particular time and we look at many runs of many different models but it does a pretty good job of showing the consistently suggested setup going into the end of the year and I didn't want to waste your time with 10 different model graphics for 150hrs out (which is kind of far). A few things I'm looking at in the above image: I'm not sold just yet that we will see a 1060mb high-pressure system. That is extremely high, almost record breaking, and I personally think that is overdone. I'm not necessarily saying we won't see it either but the strength of that feature is instrumental in just how cold it gets because it directly determines just how much cold Canadian air gets tapped into as well as how far South it goes and I can not jump on that bandwagon yet. Again, I feel somewhat confident that we will see a relatively similar setup with a high across the central U.S but the small details make the difference. 

Here is a "spaghetti plot" showing multiple different model forecasts of mean sea-level pressure in the same time frame as the GFS image. You can see that there is some consensus on the general surface pattern but that's really about it. 

Basically, the moral of the story is stay bundled up, make sure family, friends, and anyone else you know is prepared for the possibility of dangerously cold temperatures, and stay tuned for frequent updates while we stay on top of this as things come together.

DKK