It is not unusual for land to ascend into the clouds in regions where Moutains abut large valleys or gently sloping plains. This is especially apparent in California on either side of the Central Valley. The toggle above shows IFR Probability fields at 1645 UTC on 9 March, and a high-resolution topographic image. High IFR Probabilities are well correlated with high terrain. This is something a user must consider when using the product.