Producing these outlooks is very different from forecasting. Forecasting weather is basically the application of physics and math to the atmosphere through the tool of numerical models.
Seasonal outlooks like the ones for March, April and May can use a number of tools including historical analogues and statistical methodologies, and the persistance of typical flow patterns.
Also important are patterns of atmosphere-ocean interaction. To the public the most recognizable pattern is El Niño/La Niña.
There are others like the Madden-Julian Oscillation of the tropics, the Arctic Oscillation, the Antarctic Oscillation, the North Atlantic Oscillation and the Pacific North American Pattern. Essentially these all describe and quantify atmospheric flow patterns and their persistence in different geographic regions of the globe.
For example La Niña interacting with the North Atlantic Oscillation is blamed for the relatively harsh winter of 2010-2011 in Cincinnati. For the winter of 2011-2012 La Niña interacted differently with the North Atlantic Oscillation, because the NAO had changed, and though both winters were La Niña winters they were very different.
If a blocking pattern is expected to persist only slow changes to the jet stream flow may occur and as a result changes in the weather will be forecast to be slight or very slow.
Using all these tools the CPC issues extended outlooks from 5 days to 1 year in the future.
Here is what March, April and May are expected to bring:
The top map, precipitation outlook shows the La Niña "bullseye" of precipitation (as I call it) will continue over the Tristate. It is smaller and weaker as the La Niña. pattern starts to ease.
Temperatures here are expected to be warmer than average.
So at this point a repeat of the record-setting wet weather of Spring 2011 seems unlikely.
By the way CPC thinks Cincinnati will have about normal precipitation and warmer than normal temperatures for Summer 2012.
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