(BIVN) – The next episode of lava fountaining in the ongoing eruption of Kīlauea volcano could begin at any moment.

Scientists with the USGS Hawaiian Volcano Observatory say revised models suggest Episode 33 is now likely to start between today, September 17, and Saturday, September 20.

“The appearance of magma within the north vent suggests that episode 33 might arrive earlier than tilt-based models predict,” the Observatory noted on Tuesday night, noting that Episode 32 showed similar behavior.

Gas pistoning events were occurring at the north vent on Tuesday. “Magma rises and becomes visible in the vent,” the Observatory scientists described. “Rapid drainback is marked by small spatter fountains and a spike in seismic tremor, 10 to 15 minutes apart.”

This story will be updated when the USGS HVO posts its daily update for Wednesday.