Great Sitkin (ORANGE/WATCH): Faint thermal signal observed in Suomi VIIRS MIR image from 13 Dec 2025 13:20 UTC (attached) and 13 Dec 2025 15:01 UTC, in NOAA-20 VIIRS MIR image from 13 Dec 2025 13:41 UTC, and in NOAA-21 VIIRS MIR image from 13 Dec 2025 14:31 UTC. The thermal anomaly is very faint despite clear viewing conditions. Nothing was observed in clear web camera views over the past day. Nothing was evident in TROPOMI or VIIRS SO2 data.

Associated Images:
375mAKKN-MIR-d20251213t1320465416Z.png

Associated Keywords:
Elevated surface temperatures: barely elevated;
Cloud cover: mostly clear;

Shishaldin (YELLOW/ADVISORY): Small area of elevated surface temperatures at the summit crater in NOAA-20 VIIRS MIR image from 13 Dec 2025 12:02 UTC (attached). The thermal feature is probably from hot gasses in the crater. Clear web camera views showed minor to no vapor emissions at the summit, possibly because of high winds at the volcano. Nothing was evident in TROPOMI or VIIRS SO2 imagery.

Associated Images:
375mAKSH-MIR-d20251213t1202721825Z.png

Associated Keywords:
Volcanic clouds: steam/water;
Elevated surface temperatures: barely elevated;
Cloud cover: mostly clear;