Sunday, December 1, 2013

End of Week Winter Storm

Things could start getting active this week in the winter weather department.  Bitterly cold air will be on the move from Alaska/Canada and moisture could be coming north through the Mississippi River/Ohio River valleys.

Before I get too far in to this I want to remind you that the items I am going to discuss are still MANY days away.  Things can and likely will change in the forecast.  The data I am going to show you is not the actual forecast but instead a weather computer model projection of what could happen.

Ok, now that all of that is out of the way lets talk about later this week, specifically in Missouri, Illinois, Kentucky and Indiana.

One basic concept we need to discuss before going any further.  Cold air is denser/heavier than warm air.  Hence, hot air balloons rise.

All computer forecast data is indicating COLD air will be on the move through the central United States late Wednesday and Thursday.

Projected Surface Temperature - 6am CT Thursday
(Click image to see larger version.)
The cold front will be somewhere near the Ohio River by Thursday morning.  Again, keep in mind that cold air sinks, so the cold air will undercut warmer air, which will reside a few thousand feet in the sky.

Temperatures at the surface will be dropping and it will be cold at the end of the week and cold for the weekend.  Here is a look at forecast temperatures from the European forecast agency's computer model for Friday afternoon.
Projected Surface Temperature - 12pm CT Friday
(Click image to see larger version.)
Computer models also project a couple waves of energy riding up and over the cold front.  The moisture will be riding in the warmer layer above the ground.  As the moisture falls it will encounter the below freezing air.  Depending on how thick the layer of warm layer and cold layer is will determine what type of precipitation it could be.  In other words, we could be talking a cold rain, freezing rain, sleet and/or snow.

At this point, it is too difficult to say with any certainty the form will be.  We are talking about trying to determine the temperature in a layer of air along with how thick the layer will be (A few hundred feet or thousands of feet?) for something that is 96-120 hours away.  That being said, at this time, I think there potential for snow and/or freezing rain.

What could make this interesting is there could be a couple waves of moisture and there could be ample moisture to work with.

Here is a look at the National Weather Service’s Global Forecast model, the GFS, using a program called BUFKIT.  Specifically, the data is for Cape Girardeau.  Keep in mind when looking at the data, the timeline runs from right to left.
12z Sunday GFS for Cape Girardeau
(Click the image for larger version.)
The colored bars indicate what the program is projecting what form the moisture will fall.  Green = rain | Orange = sleet | Red = freezing rain | Blue = snow.  See all the green and blue?  Right, neither do I.  It is showing up as red.  That means the software/computer model is suggesting it could be falling in the form of freezing rain.

I mentioned "ample moisture".  The GFS is projecting 0.4" to 0.8" of liquid Thursday through early Friday morning for much of southeast Missouri, southern Illinois and western Kentucky.  The European computer model is also putting down some decent moisture (0.5" to 0.8") for the same areas through Friday afternoon.  The one difference is the European model is suggesting it would fall as snow, especially north of the Missouri bootheel and western Kentucky

Also to note, there are hints of another round of moisture coming up through the area Sunday in to Monday.

At this point this is nothing to get concerned over.  My "Freak-Out-Meter" is at maybe a 2 out of 10.  However, I point out the possibilities for later in the week to try and get you to pay attention to the forecast over the coming days.  As more data becomes available, as the computer models are able to sample more of the atmosphere, we will start to get a better idea of what may happen.  As I like to say... Stay tuned.

Bottom line... It is going to turn much colder for the end of the week and the weekend.  There is potential for rain, snow, and freezing rain.

1 comments:

Thank you John for keeping us here in Missouri informed! Your blog is my go to when winter weather arrives.

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