The Disturbance Impact Assessment System (DIAS) is a computer software package designed to assess and predict the impact of solar flares on high-latitude HF radio communications. The analysis spans the period between the flare onset (T0 hours) and the expected subsiding of its effects 5 days later (T120 hours). DIAS supports a HF communications system and when integrated into it, its operation will be entirely transparent to the user. A stand-alone PC version was designed for tutorial purposes. Key features combine the capabilities of the algorithmic PROPHET HF signal assessment system with expert system technology. The initial system provides qualitative advice and warnings. The rule sets in DIAS cover the following types of disturbances: (1) sudden ionospheric disturbances, (2) polar cap absorption, (3) ionospheric storm, (4) auroral zone absorption, and (5) auroral sporadic E and auroral E.