Agreed...this has been a bit problem is a quite a bit of dry air to contend with. I think the airmass is even drier then Monday's. It's going to take some time to really saturate I think.
Also, the storm ingests a ton of dry air from the southwest. Looping RH at 500/700 is pretty uneasy looking. Sure, where you're lift is stronger and ulvl divergence is greater you'll offset this some, but we're playing with time here.