Possible Winter Weather next Weekend 12/2/18 Morning Update

Sunday, December 2, 2018 - 9:00am

Good Sunday Morning everyone! I started posting yesterday about the chance for some wintry precipitation next weekend. This morning I am able to start to talk about some of the timing and potential impacts for this system. Please keep in mind as you read through all of this that there are two factors you need to remember. 

  1. Models do a horrible job of differentiating between rain/snow and ice accumulation. Some of the accumulations you will see in the model data look extremely high. Even though its possible you could see accumulations this high for the event it is highly unlikely at this time. There are ingredients to consider, Warm air aloft, the timing of the moisture arriving and leaving the area, Ground and soil temperatures. 
  2. This is still a system that is around 6 days out. There is still plenty of time for the data to change and this could easily be a rain system or nothing at all. 

I mention these factors first because anyone can post model data and scare you into a false sense of concern. I am here for credibility and to keep you informed of the most likely scenario. 

With all of that said let's take a look at the models and what they are showing as of this morning. There are 2 min models that I focus n this far out and then I use a mix of all of the available model data for an ensemble approach of what you could see. Let's start with the GFS Model Data.

 

 

Based on the current timing with the GFS we could see precipitation move in late Friday evening in the form of rain as warm air will still be out ahead of the moisture. As we move into the overnight hours we will see the chance for rain to transition into mix of rain and snow. The precipitation could turn into all snow as the air aloft begins to cool.

 

 

As we move through the day on Saturday we could see a warm nose of air begin to push in that could cause a transition to a snow and freezing rain mix. As the warm air continues to move in we could then see based on the image below a period of sleet. This could cause travel problems on the backend of the system as ice would form a layer over the snow that has already accumulated. (Remember this is likely but not a sure thing at this point)

 

 

The GFS I feel is doing a good job at this point of laying out all of the likely possibilities with this system as indicated below. We are likely to see all elements of precipitation from rain, snow sleet and freezing rain. The real question at this point is for how long with each type of precipitation as this will make all the difference in the world for accumulation totals. 

 

 

Now with the image above the better chances for possible precipitation at this point are rain and snow with rain having most of the impact. As we move through the overnight hours we could see the change to more of a mixed bag of accumulation with cold air moving in aloft. 

 

Here is where I feel the GFS models are struggling. The potential for accumulation. As I mentioned at the start of this blog post. Models do a horrible job differentiating between the types of accumulation. The six inches of snowfall here to me is a bit overstated. I will get into how much snowfall accumulation I think we could get at the end of this blog post.

 

Now let's take a look at the European Model and what the data is showing from that model for next weekend.

 

 

The European Model is showing moisture moving in a bit later into the early morning hours of Saturday. Now if this occurs we will see less rain on the front end and more of a mixed bag of wintry precipitation from the system during the daytime hours Saturday. 

 

 

The European model shows the system moving out later as well. The system would move out Sunday Morning and would likely end with some icy accumulation on the back side. 

 

 

Here is where the European Model changes from the GFS. Both models feel we will get rain, snow, sleet & freezing rain from this system. The timing is a bit different. The accumulations are vastly different. The European Model is leaning toward 11 inches of accumulation around the county. I feel at this point this is vastly overstated. Again the models do a horrible job of differentiating between the different types of accumulation totals. When you mix in snow and ice. The accumulation totals get inflated. 

 

 

The Ensemble Models seem to have a better grasp on the accumulation totals around the area and the county. The ensemble models are showing accumulation totals for snowfall of 4 inches for the county. This certainly seems more likely at this point based on the current timing of the system. 

 

Here is how I am forecasting this event at this point. 

 

  • Rain will move into the county late Friday evening into early Saturday. The later the system arrives the less rain we will get with more of w wintry mix of precipitation instead.
  • During the overnight hours of Saturday morning we will begin to see snow move into the county. 
  • As we move through the day on Saturday warmer air will begin to move in aloft causing a transition to a mix of snow and sleet. 
  • The system will begin to pull away late Saturday evening into the overnight hours of Sunday morning ending with a brief period of freezing rain and possibly all rain before the moisture moves out. 
  • Accumulations will vary. Snow at this point looks to have the most accumulation with around 3-5 inches around the county. Ice accumulations of around a tenth of an inch are possible with this system.

As we move through the week I will of course keep you updated right here and on my social media outlets. Remember this is still 6 days out and much of the forecast will change as we get closer to the event. As always thank you for following Rowan County Weather!

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