Lag? What lag? Metars are issued every hour aren’t they. How much lag can there be?
Lag between the issue time of the METAR and the time the METAR is processed by the Azure servers and served to your sim.
Might be seconds, might be days. We’ve seen it all happen.
Keep in mind that clouds at FL410 (or high level clouds that aren’t cirrus) can be associated with an upwind thunderstorm. Not the top of a thunderstorm, but the “blowoff.” Think “anvil” in the weather books- however it can extend for several hundred miles as carried by winds aloft.