There's update for FSUIPC at ASE homepage, that enables it to report weather to Radar Contact and other apps in DWC mode (no more excuses for: no Wx radar? kidding...), which means that most of problems will/might be resolved this way. DWC mode with Visibility Graduation plus REX2.0 textures is all I need for weather. It looks great and it works great.

RC first looks at AI patterns and that has priority regarding runway assignment on approach if the runway meets the necessary minum characteristic for the class of aircraft. If AI are not active then weather plus runway characteristics dominates.In the ASE manual unless revised it suggested that FS9 users use FSUIPC to get the same benefits as DWC for weather smoothing so global mode need not be used in FS9.