Deforestation reduces the magnitude of surface biomass that can actively transpire water vapor back to the atmosphere. Air that is less humid must rise to higher altitudes before clouds form. Mountainous regions downwind from deforested areas, therefore, likely will see higher clouds as a result. Lawton et al (2001) point out that in some areas like Costa Rica, these montane regions also host tropical rainforests that depend on persistent fog (low clouds). Deforestation upwind of these areas likely will have substantial effects on montane ecosystems.
Reference
Lawton, R. O., U. S. Nair, R. A. Pielke, Sr., and R. M. Welch, 2001: Climate impact of tropical lowland deforestation on nearby montane cloud forests. Science, 294, 584-587.