IWX pointing out that the NAM is bad for ice throughout their northern CWA, the just above ground temps are below freezing
Have favored the cooler models for the shallow cold air Saturday
that originally included just the GFS, but now the NAM is showing
a very shallow layer of cold air just above the surface that will
likely be below freezing for several hours. Believe the greatest
winter weather impact if the surface temperatures are cold enough
will be from freezing rain. NAM BUFKIT 00Z and 06Z runs showed
several hours of freezing rain Saturday into Saturday night. After
coordination with Chicago and Grand Rapids NWS offices have
greatly increased ice amounts. Given the strong upper level system
just reaching the Calif coast, concern that upper level sampling
of this system may still be lacking, so confidence was not high
enough to post a winter storm watch for ice. Otherwise, Sunday
will be dry with highs in the 30s. Travel late Saturday and Saturday
night may become hazardous depending on weather types and pavement
temperatures.