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.

"Snowfall, Sleet & Ice Oh My!"

It never can be an easy forecast around here. Why can't it just be all snow? It would sure make forecasting this storm much easier.

By now, you might have heard about a winter storm headed our direction. It still indeed is. The National Weather Service (NWS) in Memphis, St. Louis, and Paducah has issued a Winter Storm Watch for the entire Heartland (Southeast Missouri, Southern Illinois, Western Kentucky, Northwest Tennessee). The watch is in effect Monday evening through Tuesday evening.

There are still a lot of uncertainties with the storm.

1. What will temperatures be at different heights of the atmosphere?
2. How much moisture is there to work with?
3. What type of precipitation will we have?
   

Looking at temperature profiles are interesting at times. Basically, I am talking about taking a slice of the air above the ground and looking at it from the side. Think about it this way. When you are looking at an aquarium, you can look down at the water just above the bottom. Then you can move up the glass until you see the waterline. It is just a cross section of the water in the aquarium. That is what we have to do when determining what type of precipitation we will have.

Here is an example of what one of the computer models is suggesting for Monday/Tuesday. It allows us to see the cross section over Cape Girardeau.

If you click on the graphic you can see a larger version. I want you to notice the yellow lines on the screen. At around 5k to 10k (5,000 feet to 10,000 feet) see the 0 line? That is the freezing line at different heights above the ground. Notice all around the outside of the 0° line there is colder air. Inside there is warmer air. That means that anything falling through that area of the atmosphere will warm up and probably melt to liquid.

Also notice how it then gets below 0° near the surface. That is when the moisture would refreeze. In that situation we would probably be talking about freezing rain. Freezing rain = ice = yuck!

When you look at the graphic, you see different colored vertical bars. That is how much precipitation and the precipitation type. Green=rain Red=freezing rain Orange=sleet Blue=snow. (Also, when looking at the graphic, the time runs from right to left. I know it is backwards, but I didn't write the program. haha)

This particular model is indicating mainly freezing rain. Not just a little freezing rain, but a lot! On the order of over an inch. That would definitely not be good!

When I look at one of the cross sections from this model for Farmington, Missouri it indicates mainly snow. And a lot of it! This specific model is trying to suggest 8.1" of snow.

Again, this is just a model. A suggestion. When I forecast I look at a minimum 5 computer models. For major snow storms, I might take a look at 8 models.

If you were watching Heartland News at 10pm Saturday night you might have heard me say that I had a gut feeling this could be a bigger ice storm than snow storm. My gut still feels that way. (Although, I am also hungry, so it could be telling me to eat something.) As is usually the case, we are going to see the dividing line between freezing rain, sleet, and snow over the top of us. I think some people could get some heavy snowfall out of this. I think some could get a decent amount of freezing rain.

Here is a map showing what one of the computer models is calling for with regards to freezing rain.

Here is what the forecasters at the Hydrometeorological Prediction Center (or HPC) are forecasting. (This forecast was updated Sunday morning.)

Like I mentioned before, there are still a lot of uncertainties with the storm. Some of the models are trying to bring only a tiny bit of moisture through the area. If that were to be the case, then the numbers would be held down drastically.

I'll be looking over the models this afternoon while I try to put together my forecast. Hopefully, I'll feel strongly enough about a snow/sleet/freezing rain amount forecast to have it on TV tonight at 10pm.

I now need to go find my colored markers. Even though we have all kinds of computer technology to do things, I still like to take out a map (on paper) and mark it up with the colored markers while putting together the forecast.

So all of that said, what are you hoping for out of the storm?