heavy rain advisory
An official weather advisory issued when heavy rain is expected, below the level of a warning (警報).
The Japan Meteorological Agency issued a heavy rain advisory at 3 p.m.
大雨警報 is a more serious warning indicating that heavy rain is already occurring or imminent, while 大雨注意報 is a lower-level advisory calling for caution.
Compound of 大雨 (heavy rain) + 注意報 (advisory, from 注意 'caution' + 報 'report').