Sunday, January 25, 2009

"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?

6 comments:

John;
where do you get the models at, are they on the web? I just started reading your blog,well done. Keep up the good work.

John,

What am I hoping for out of this storm?? Personally, I am hoping for a miraculous error in weather forecasting...I'd be happy till next winter if the models are all wrong and instead of tree-breaking, roof-crushing, power-outing ice we have an early spring thaw that's here to stay!! At this moment, global warming could slap me in the face...at least I might be able to go back to wearing only ONE pair of socks to keep my feet warm...lol...guess I'll have to start recycling some of those darn old plastic Wal Mart bags. Maybe we could lash them together and form a protective canopy over the Heartland! They will never disintegrate and go away, you know. Just kidding, though I wonder if it's a global warming effect that has taken us from the mostly snow events we had when I was a child to more of these ice events that seem more and more common in the Cape area. Hmmmmm...

P.S. Is it obvious how I feel about winter and its weather?? :-)

Pretty cool to have a weather blog. I agree with one comment that in the last three or four years we experience more in the way of ice storms than a pure snow event. I still would wager some money that warmer air will turn this forecast around. Last year B.A. and everyone else within 12 hours of a storms onset said that up towards Perry County and Jeff. county Illinois upwards of a foot of snow could be a possibility. 3-4 inches of mostly sleet was the result. I believe that was the one that iced over Carbondale and surrounding areas really bad. A real push of warm air did that one. Tough job predicting the future huh:-)

John,
I would prefer just snow, and lots of it.

I'm wanting snow!!!! Enough to shut everything down and have a day off!

I'm wanting snow!!!! Enough to shut everything down and have a day off!

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