Commercial Fixed Wing
Flight Crew Air Transport Pilot (ATP)
Situational Awareness
Inflight Event / Encounter Fuel Issue; Inflight Event / Encounter Weather / Turbulence
Flight Crew Diverted
Weather; Human Factors; Procedure
TAF visibility was 3 SM between an hour before and hour after arrival. Forecast to drop to 1 SM roughly six hours after our arrival. We picked up the ATIS on arrival (1/4 mile; ceilings indefinite 002). Promptly contacted dispatch to work out a viable alternate. Discussed alternatives (ZZZ would have resulted in Min Fuel with ~2.3 fuel remaining); ZZZ1 is not in our Ops Specs; ultimately decided on ZZZ2 as our alternate. The RVR was fluctuating between 1600 and 2000. RVR dropped to 1600 (needed RVR 1800 for 19C) just prior to reaching FAF; we went missed. Dispatch wanted us to try again; which was not going to happen with ZZZ2 deteriorating as well. Proceeded direct to ZZZ2 (ATIS: vis 2 1/2; 003 overcast) and landed. Though not required; I should have requested an alternate with TAF reading 3 SM; light winds; and a tight spread. [Suggest] Dispatch Provide an alternate whenever borderline necessary. [And] Training for dispatchers on how to look out for 'unexpected' deteriorating weather; classic case-in-point above. [Lastly] Monitor destination weather and communicate deteriorating weather with pilot's enroute to help the crew start planning prior to arrival when workload increases. [Suggest] Company Stress/communicate conservative fuel planning to dispatchers when conditions anything less than ideal. [and] CAT II capability would have given us extra margin for safety; and it would have allowed us avoid the diversion.
While no alternate was required; pilots and dispatchers need to consider local weather patterns; (i.e. springtime; airports near rivers or in a valley; dawn or dusk; tight temperature and dew point spreads; could be favorable to fog formation). Take this into consideration for fuel loads; and when planning for or requesting an alternate airport. Dispatch watching for deteriorating conditions and notifying the flight crew enroute with updated conditions could be helpful; and reduce workload in the descent and approach segments of flight; and having the ACARS capability to receive ATIS enroute would allow the flight crew to monitor marginal weather conditions and alert dispatch so planning could be accomplished in a timely manner.
Flight crew reported they were legally dispatched to IAD with no alternate; but were forced to divert to an alternate when weather deteriorated enroute.