A foot of new snow fell in the Panhandle on Wednesday, while rivers and creeks already swollen from melted ice and snow jumped their banks across eastern Nebraska.State officials urged Nebraskans to stay put in areas where heavy snow and high winds have made travel dangerous, and asked those threatened by flooding to heed evacuation warnings and to avoid water that has spilled over roads.The weather system — which Gov. Pete Ricketts and other state officials alternately described as “unprecedented,” “significant” and “prolonged” — flooded several communities and caused the interstate to be shut down for hundreds of miles.