That's the random element of the forecast coming into play. The conditions were boarder line light-rain/overcast. I did not want to make the forecast totally accurate. It did 'almost' rain.
If I remember correctly, wunderground said 20% chance of light showers. If the potential of rain is forecast but the randomness of the weather generator decides that it will not rain (like rolling a 10 sided dice and saying 'we have no rain if we roll higher than a 2') then, we will get overcast conditions. That is what should have happened.
