Hmmm... the NWS has a SW-NE axis of heaviest snow (6-12") from the Omaha suburbs to Des Moines and Ames to Waterloo to Decorah in the far NE. The NW and SE areas are mostly excluded, including the Quad Cities and the strong Santorum/Huckabee areas NE of Sioux City. Dubuque is right on the edge of heavy vs. light snow. Temperatures are generally in the mid-20's to low 30's.
By Upper Midwest standards, this isn't all that much snow or all that cold. To the extent the storm does impact the caucus, I would expect it hurts the candidates most dependent on relatively upscale urban voters with college degrees, given that Des Moines and Ames are in the bullseye. That's clearly bad news for Sanders, and on the Republican side probably hurts Rubio most.
But again, this is Iowa and they are used to snowy winters. If, for example, the VA/MD/DC primaries had been held last Monday, this would be a very different story!
After taking into consideration the Weather.com poll, I think you are right. Rubio and Sanders will be hurt.
I am changing my projection of Iowa winners to TRUMP and Clinton.
