Saturday, December 19, 2009

11:00am Christmas Eve Storm Update

New data has come in from the morning's computer model runs of NOAA's global forecast model. It has taken the storm a little further north meaning more rain for southeast Missouri, southern Illinois, western Kentucky, and south/central Indiana.

Here is the GFS forecast panel for 12pm CT Thursday, December 24 from the 12z 12/19 run:

Here is a look at a visual representation of accumulated snowfall over a period from this morning through 7pm ET Saturday. (Click on the graphic to see a larger view.) The graph is called a meteogram. The dark blue line indicates the 1am CT run of the model. The brighter blue line indicates this morning's 6am CT run of the model.

Cape Girardeau, Missouri:

Indianapolis, Indiana:

Snowfall amounts are obviously not as impressive as they were with last night's run. For Cape Girardeau it is showing very little snow. Instead it is showing rain. The heaviest snow is depicted across northern Illinois. In fact, the model is putting down 11" of snow for Chicago.

The flip-flopping going on with the model is to be expected. In fact, this happens with almost every winter storm we have.
I wanted to show you what we, meteorologists/forecasters, have to deal with every storm. This is why it is sometimes difficult to tell you 4-5 days in advance how much snow we are going to get. We continually get conflicting information.

Here is the storm we are going to be watching. It is currently over the eastern Pacific Ocean.

The models should start to get a better consensus once the surface and upper-air portion of the storm makes its way onshore Sunday/Monday. Once onshore, the models can have a better sampling of more weather elements in the storm at the surface and 30,000 feet up.

If this storm should track further south than this morning 12z run, then we could be talking about higher snowfall amounts. If the storm tracks further north, we are talking more rain. For a big snow in southeast Missouri, southern Illinois, and western Kentucky we would need the surface low to track over southern Arkansas to Memphis, TN to Nashville, TN.

For people in central/southern Indiana it would need to track north of the previously mentioned track for higher snowfall amounts.

I will be continuing to update the blog with new information as we get closer to the storm. I will also be sending out updates via Twitter. Follow me on twitter at

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