Commercial Fixed Wing
Dispatch Dispatcher
Situational Awareness
Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural FAR; Inflight Event / Encounter Weather / Turbulence
Air Traffic Control Provided Assistance; Flight Crew Diverted
Company Policy; Human Factors; Procedure; Weather; Chart Or Publication
Seattle was forecast to be 1/2 SM at [arrival time]. I requested that [flight] be protected to CAT3 due to the low weather. I went about my flight planning as usual. Nothing in the NOTAMs stood out as being unusual (16L/34R closed due to construction). With the new SFP (Short Field Performance) in place; I selected IFR conditions and ran the calculation. Selecting the IFR conditions did not add any extra fuel above the MIN RPF of 20 minutes. Finding this unsatisfactory (common occurrence when selecting IFR conditions); I added an additional 10 minutes worth of fuel; finalized the flight plan and sent it. Flight took off without further incident. Approximately abeam PDX; I updated the crew with the latest METAR and RVR. While on downwind; the crew advised that they'd be unable to land due to Tower requiring 600 feet. RVR. Thinking I missed a NOTAM; I double checked them and again nothing mentioning that requirement. I called SEA Tower inquiring that requirement. They advised that due to the construction; the SMGCS system was INOP and needed 600 feet. RVR to operate on the ground. So [the flight] could make a CAT3 approach and land but would be unable to maneuver around the airport. I advised the crew and they continued to hold until they diverted to planned alternate of PDX. This was occurring during shift turnover. I advised Day Shift that was taking over that they were diverting to PDX. I sent an message to the folks working SEA of the requirement that was not in the NOTAMs.Lack of NOTAM or Chart Change Notice indicating SMGCS being INOP or operating with higher than normal minimums. With the IFR conditions; I should have added more than 10 minutes fuel knowing that ATC will be operating in a less than optimal arrival rate and RPF adding no more fuel than if I selected a VFR day. I hesitated adding more fuel knowing that it'd show up on a report and possibly getting questioned about adding fuel above the SFP requirements.
Dispatcher reported the inbound flight was unable to land due to field restrictions from the Surface Movement Guidance and Control System being inoperative without a NOTAM.