A new lava dome is forming in the crater of Cleveland Volcano.  In response, scientists at the Alaska Volcano Observatory bumped the aviation alert level from yellow to orange on Wednesday.

It’s the fifth time since July that the Observatory has raised the alert.  A series of small eruptions earlier this month removed the lava dome that had been forming since January. None of the eruptions produced a significant ash cloud and there’s been no activity at the volcano since March 13.

Cleveland’s eruptions often draw international attention because the remote volcano lies on a major flight path and previous eruptions have disrupted air travel.

In a release about the growing lava dome the Observatory noted that “sudden explosions” with ash clouds “exceeding 20,000 feet” are possible at any time.

There’s no real-time monitoring network on Cleveland, but the Observatory does have an alert system that can detect the lightning that accompanies major ash clouds within minutes.