Construction beginning/end
The Dwarvish decide that when the Great Storm returns that they will retreat to the safety of the underground caverns. At which point they do, they will close the entrance behind them and ensure their survival into the near future. The Dwarvish existence in the timeline stops here - and are modernly considered extinct.
The Dwarvish were the least affected people when the Storm came to pass - but this did not leave them the better off. For weeks they starved in the confines of the caverns, food-less and at times heat-less as supplies ran out a mere 8 months into the storm. The Dwarvish tribe made a species-wide agreement that when the next storm struck that they would be better prepared, better equipped and wouldn't lose a single life. Their solution was to prepare themselves for cave life by preparing mounds of supplies enough to last several years worth - should the Great Storm ever last longer then the initial year. This involved making infrastructure better then the current log based systems and preparing themselves for all situations possible from the confines of the mountains.