TFree

Thanks a lot for the sources of info and ideas on how to address the temp index parameters

I am using HEC-HMS to model snowmelt, and have several questions: 1. What are reasonable values for the ATI (antecedant temperature index) meltrate function? Similarly for ATI meltrate coefficient? Alternatively, what are some reasonable methods to determine these values? It isn't clear to me what these really are. 2. When I run the model, I get an error message that melt rate is undefined for my first time step (even though I have numbers for ATI function and coefficient. Any insight as to why I am getting this error message and how I can correct it? Thanks, TFree