This app was mentioned in 1 comment, with an average of 1.00 upvote
/u/joshuat6 wrote an app just called "wX" I just started using it, but it already seems extremely useful for both forecasting and "day of" type stuff.
As other have said:
Pykl3 (android only)
RadarScope (apple and android)
SPC Mesoanalysis Viewer (android)
Check to see if your state has a mesonet-style app. Oklahoma has Mesonet and it's a pretty powerful app imo.
HazWx someone else mentioned. . . but I couldn't imagine using it on cell or even tablet. I have it installed and I think I've loaded it up at work once or twice just to look at something specific.