What will the weather be like two weeks from now?

At Climate Science a post by Roger Pielke Sr., WG1 IPCC Chapter 1 - More Scientifically Erroneous Statements has this to say about the IPCC:

Their claim that

Projecting changes in climate due to changes in greenhouse gases 50 years from now is a very different and much more easily solved problem than forecasting weather patterns just weeks from now.

is such an absurd, scientifically unsupported claim, that the media and any scientists who swallow this conclusion are either blind to the scientific understanding of the climate system, or have other motives to promote the IPCC viewpoint. The absurdity of the IPCC claim should be obvious to anyone with common sense.

Emphasis added.

The above quote indicates that the writers of the IPCC report are rather concerned about those skeptics who question why we should believe their predictions of CO2 driven climate change in the coming century, when everyone knows the unreliability of short to medium term weather forecasts. They were concerned enough to address the issue in their report.

So, just what will the weather be like two weeks from now? Has modern science really improved notably on the predictions of weather found here?

More importantly, why should we believe the climate predictions of the IPCC?