Tuesday, December 3, 2013

Slip Slidin' - Tuesday Morning Update

Not a lot of time this morning to update the blog but I did get a few minutes to look over some of the new data trickling in from the morning computer model runs.

First take-away... The models are a little further north with the track of the system.  Which was expected.

There is a lot yet to be determined on placement/precipitation type.  As usual, the National Weather Service's NAM computer model is a little hyperactive with the amounts of precipitation.

Let me run you through several maps that can give you an idea of where the models are placing different types of precipitation.  Before I say anything else, PLEASE remember that this is not locked in stone.  These are just computer model projections and far from the actual forecast.

First, here is the NAM's projection of snow accumulation through 6pm CT Friday.

12z NAM - Snow Accumulation through 6pm CT Friday
(Click image to see larger version.)
 Now here is the NAM's projection of sleet accumulation through 6pm CT Friday.
12z NAM - Sleet Accumulation through 6pm CT Friday
(Click image to see larger version.)
Now the dread "ice" word.  Freezing rain accumulation through 6pm CT Friday.
12z NAM - Freezing Rain Accumulation through 6pm CT Friday
(Click image to see larger version.)
As you can see, the NAM is perhaps a little overzealous, especially with snow in the St. Louis metro.  (12"+?!?!)  The model is also heavy handed with the sleet for southeast Missouri and southern Illinois.  I could buy this scenario.

This event is at the edge of the model's projection view.  I have a feeling we will see these numbers dropping over the next 24-36 hours.

Now a look at the National Weather Service's Global Forecast model, the GFS.

Here is a look at what this morning's run of the GFS is suggesting for snowfall accumulation through 6pm CT Friday.
12z GFS - Snow Accumulation through 6pm CT Friday
(Click image to see larger version.)
 GFS sleet accumulation through 6pm CT Friday.

12z GFS - Sleet Accumulation through 6pm CT Friday
(Click image to see larger version.)
Finally, the GFS suggestion for freezing rain (ice) accumulation through 6pm CT Friday.
12z GFS - Freezing Rain Accumulation through 6pm CT Friday
(Click image to see larger version.)
Observation of the GFS... First, it is further south than the NAM.  It is also not as bullish with snow.  The GFS tries to hit the sleet and freezing rain a little harder.

Again, the models should start to line up better as we get closer to the event.

Bottom line... Cold air is expected to arrive later this week.  Moisture will be in place and there could be a mix of rain, freezing rain, sleet and snow across parts of southeastern/eastern Missouri, southern Illinois, western/northern Kentucky, northern Arkansas, northwest Tennessee and central/southern Indiana.  If you have travel plans Thursday-Saturday pay close attention to the forecast.

Reminder:  Follow me on Twitter for more information as it becomes available.  @johndissauer

Freak-Out-Meter:  4 out of 10

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