Scott beat me to it. There are also some non-met positions.
Hydrometeorlogical Technician (HMT)--Quality controls data for climate summaries and makes sure the current incoming data (ASOS, river gauges) isn't out of whack. If problems with the instrument sites are suspected, the HMT reports them to the ETs. Also responsbile for upper-air launches. Some offices also have one HMT that is designated the Observation Program Leader (OPL). The OPL oversees the Data Acquisition operation including the daily duties of the HMT and Intern. The OPL is usually in charge of maintaining the Cooperative Observer program for the WFO, including make house calls to maintaining the coop observers' equipment.
Electronics Technician (ET)--Maintains any electronic equipment that the WFO may be responsible for. This could be anything from the WSR-88D, profilers, local ASOS, or any computer hardware inside the office.
Electronics System Analyst (ESA)--Head of the ET staff.
Administrative Support Assistant (ASA)--The Office Manager of the WFO. The ASA deals with the Human Resources and general office needs of the WFO.
Typically, during an event, personnel are called in on their day off, called in early for their shift, or held over to work the event. Again, this is all dependent on the actual situation. The Senior Forecaster, acting as the shift supervisor, is constantly evaluating how the event is evolving and adjusts personnel numbers and duties as needed.
Each individual WFO is going to have slightly different methods (staff numbers, shift schedules, delegation of routine duties, etc.), but they all do basically the same things, with the exception of certain products that vary by location. For example, you're not going to see AMA issuing Avalanche Forecasts.
