Air carrier Dispatcher relates the impact of excessive workloads on his ability to monitor the needs of the flights under his purview.

Narrative

During work in Dispatch on the 'swing shift' excessive workload requirements caused a complete failure on my part to maintain operational control of flights on my 'watch' due to an inability to monitor weather and enroute progress of various flights. Due to marginal weather conditions (both forecast and unforecast); runway conditions with reduced braking due to snow and ice on the runways; and the performance considerations demanding close monitoring/evaluation; I realized later that I had completely neglected numerous flights originating from Southern California. I was totally unable to monitor any weather; or weather trends in California; and to some extent in Oregon; where some of the flights on my 'flight watch' originated and terminated. This is the first ASAP report I have filed regarding this workload issue; but I have voiced my concern twice in the past in the form of a Safety Report. There have been numerous other safety reports submitted by other Dispatchers with similar experiences and concerns. There may have been numerous other ASAP reports filed also. It should also be noted that during this particular time period; there were no ATC holds; no Medlink calls; mechanical problems; or their time-consuming issues that are very common that would have only increased the workload further. I spoke to one other Dispatcher who was on duty at the time; who voiced an opinion that their workload was excessive also.