Further evidence for the influence of the spatial structure of soil moisture and temperature fields on atmospheric processes (within the boundary layer and lower troposphere) may be found in the mesoscale modeling studies of prestorm environments. Fast and McCorcle [1991] show that a heterogeneous soil moisture field induces variations in the boundary layer structure that modify the spatial distribution and intensity of precipitation from a baroclinic disturbance in central United States. Chang and Wetzel [1991] show that localized differential heating at the land surface (brought about by strong gradients in surface soil moisture content) enhance stationary atmospheric fronts that may lead to heavy surface precipitation. The mature storm environment for such baroclinic systems in mid-latitudes can potentially modify the variability in surface conditions. The spatial pattern of soil wetting by the precipitation due to these storms closes a feedback loop between the surface and the atmosphere. For example Harrington and Flannigan [1993] show that dry days for many Canadian locations may be statistically represented by a double markov process. The transition out of a drought condition is dependent on the prevailing atmospheric circulation, whether it is blocked or non-blocked westerly. As a result, the weather pattern is bimodal in terms of its transition characteristics and prevailing conditions. A significant effort to capture the two-way interaction between soil moisture conditions and baroclinicity is reported by Castelli and Rodriguez-Iturbe [1993]. They show that soil moisture gradients force modifications in the baroclinic circulation that reinforces the anomaly fields, both within the atmosphere and at the surface.