AVO reported that during 8-12 and 14 February cloud cover prevented satellite views of Bogoslof; no other data indicated eruptive activity.
At 0724 on 13 February seismicity significantly increased, prompting AVO to raise the Aviation Color Code (ACC) to Red and the Volcano Alert Level (VAL) to Warning.
Satellite images acquired through 0930 showed no ash emissions above the 3 km (10,000 ft) a.s.l.
cloud deck, and no lightning was detected.
AVO concluded that, despite the intensity of seismic activity, a significant ash emission was not produced during this event; the ACC was lowered to Orange and the VAL was lowered to Watch.
Source: US Geological Survey Alaska Volcano Observatory (AVO)