Large parts of the Northern Great Plains are peppered with small but abundant glaciated wetland complexes that are often poorly represented in both the land-surface the land-surface schemes in numerical weather prediction (NWP) models, and the land cover characterization datasets on which these schemes rely. Moreover, since the early 1990’s, the region’s spatial wetland coverage has quickly increased to record extents altering not only the dry upland vs. surface water ratios, but also the resulting land cover has altered to accommodate this new regime. This would imply an underestimation of the net surface moisture availability over the northeastern Great Plains in current operational NWP model initializations. Given previous classical work on the influence of soil moisture gradients and anomalies on the pre-storm environment, it is hypothesized that the collective expansion of these subgrid-scale structures has possibly altered the regional pre-storm environment.

We will present results from a series of numerical simulations over the northern Great Plains using the PSU/NCAR Mesoscale Model (MM5V3) for a set of surface-and synoptically-forced convective events to demonstrate the influence of these unresolved and complex features. Preliminary results demonstrate an alteration of precipitation fields demonstrate a modest yet noticeable alteration on synoptically-forced warm-season precipitation in simulations using a 6-hr lead time to the onset of convection. We will then discuss the role of these wetland systems in the evolving regional boundary layer due to the alternative surface moisture initialization regimes for longer lead times, and the impact of representing these wetland systems on resultant precipitation forecasts.