Date: 201807
Local time of day: 0601-1200
Location: ZOA.ARTCC, CA
Flight conditions: IMC
Weather elements / visibility: Thunderstorm; Turbulence
Light: Daylight
Aircraft: B737 Undifferentiated or Other Model
Flight plan: IFR
Flight phase: Cruise
Airspace: Class A ZOA
ATC / advisory: Center ZOA
Reporter organization: Government
Reporter function: Enroute
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Workload; Situational Awareness
Anomaly: ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Air Traffic Control Provided Assistance; General Flight Cancelled / Delayed
Contributing factors: Company Policy; Human Factors; Weather; Procedure
Primary problem: Company Policy

Narrative: As the mid-shifters took over LAS was in a GS (Groundstop) for severe thunderstorms over LAS and a GS was in effect for the airport. METARs showed winds gusting to over 60 knots with multiple convective SIGMETs for the area and the area going into LAS. Aircraft that were already airborne were holding short of ZLA and trickling in as they had room.Seemingly as TMU (Traffic Management Unit) left they must have cancelled the GS as no one was available anymore and all the airports in ZOA airspace began launching their LAS departures. By this point it was just the 2 mid-shifters still on position and we soon had 10 holding short of ZLA airspace over the course of a few hours with ZOA also holding aircraft and 3 of them diverting to Southern California airports for fuel. Considering we were just short of the mid-shift configuration with the lows combined the traffic was extremely busy and complex.Before TMU left we were advised that we would be going back to lower in trail requirements. By the time that came ZLA still couldn't take anyone and it was clear that everyone was making decisions before they left without talking to the sector working the traffic. ZLA could not take anyone for over an hour as they kept getting more arrivals from other sectors leading to our diverts. Talking to the sector ZLA was also under the assumption we were still ground stopped. The amount of traffic holding for LAS was unnecessary when we already had a tool to handle the traffic load and weather issues with a ground stop and GDPs (Ground Delay Programs).On top of the safety aspects how much money did the airlines spend in fuel holding and then diverting then having to continue to fly everyone back to LAS when they could have waited for conditions to improve while on the ground?The core of this seems to be that there was no TMU staffing to continue operations locally past scheduled duty day. If the domestic areas have to be ready to hold people over why is TMU not doing the same? Unless they had already worked 10 hours in which case why were they planned poorly and/or not calling in overtime to cover the night. Cancelling the GS/GDPs put everyone in an awkward and increasingly complex and concentrated operation for no reason. It clearly should have continued as the weather may have even been forecasted to improve but in the real world it did not do so on the predicted timeline.




Synopsis: ZOA Controller reported Traffic Management Unit cancelled their flow control programs at the end of their duty day even though weather was causing major delays in the airspace.