I can confirm this process was required on my end as well. Got into a situation where it was sunny skies everywhere (which, c'mon in real life on the ground would be great ). Forcing weather reloads did not help, changing from current to historic situations in both ASXP and FSGRW did nothing. I also tried to remove/re-added RWC to no avail. In the event that you wanted to further investigate this a a possible bug, I've tried to collect some info.
Here are a couple of screens that I was going to use to create a new post before I came across the above suggestion. I looked for a SMP specific log file, but didn't see one in the plugins folder. I did see that the settings.dat was updated after closing XP, so perhaps its useful to you. I've also included a log file from XP... (which I'm now realizing is almost 100mb as it's uploading). At any rate, glad to have some clouds back in sim.