I'm running the Windy.com website on Edge (always updated) and having made an "app" out of the site. That said, I see these issues whether I'm using a normal browser window or the "app" version of Windy.
The Clouds layer too frequently loads as a blank map when I switch to it. I have to switch to another layer, then back to Clouds again to actually get the layer to load. It's not an every-time issue, but it is frequent enough for me to suggest y'all need to take a look at that.
The scrubbing issue, which affects any layer with a 24h lookback timeline, goes like this: I'm on the a layer (typically Clouds or Radar) and want to look back in time to get an indication of the trajectory a storm or entire weather system is/has taken over time. So, I grab the scrubber and take it to the left. Let's say I go all the way left, i.e., back to 24h ago. I can then watch as the data loads in as indicated by the scrubber bar acting as a progress bar turning white as it goes. Once completely loaded, I begin scrubbing through. Rather than a smooth scrub through the timeline, it frequently stalls and the scrubber bar indicates that the data is being loaded again, either partially or completely. But wait... didn't it just load the last 24h worth of data? Why is it re-loading it and lagging out the scrub? I think it ought to load once and then let me scrub smoothly through that data, shouldn't it?
As an aside where the load times are concerned, it can sometimes take quite a long time to load these historical lookback data sets. Perhaps look into ways to optimize that, too?
Thanks.

