Date: 201702
Local time of day: 0601-1200
Location: SCT.TRACON, CA
Flight conditions: VMC
Aircraft: B737 Undifferentiated or Other Model
Operator: Air Carrier
Mission: Passenger
Flight phase: Cruise
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness
Second reporter function: Pilot Not Flying; First Officer
Anomaly: Inflight Event / Encounter Fuel Issue; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Flight Crew Diverted; Flight Crew Landed As Precaution
Contributing factors: Weather
Primary problem: Weather

Narrative: Enroute to PSP the forecast weather for ONT; LAX and PSP were checked. I informed the First Officer (FO) we would use ONT as a divert if need be and entered it as an alternate destination in the FMS. Approximately 1 hour out I entered the SETER4 arrival to 26R in Route 2. The actual weather and forecasted weather for PSP was ok; however; we only had enough fuel for one approach and enough fuel to make it to ONT and land with reserve fuel.Inbound to the arrival at PSP we were advised; due to traffic; we would need to hold present position. When we queried ATC for an expected arrival time they were unable to give us one; other than stating (1) aircraft just did a go-around at PSP and two other were in sequence for the arrival. ATC could not give us a reason for the go-around. On the assumption; we might be diverting; I attempted to contact dispatch; no joy. I immediately followed up with an ACARS message to dispatch requesting ONT as an alternate. Not long after I sent another ACARS message requesting the same. After 2 turns in holding and some vectoring; we reached my bingo fuel and I directed the FO to advise ATC and request ONT as a divert. We previously declared minimum fuel in holding. Not long after I noticed dispatch had issued ONT as a divert.ATC cleared us directly to PSP and the SETER4 arrival 26R. To be able to activate and execute Route 2 saved us valuable time during a very busy evolution. Enroute to PSP I filled out and sent an ACARS divert message to dispatch. We landed ONT uneventfully; however; they were not aware of our divert situation.Lessons Learned:- I've never been afraid to add fuel nor have I ever been denied. My fuel load was normal for normal day at PSP but; the weather at PSP was not the norm. After my initial pre-flight; I was leaning towards adding fuel; however; I allowed distractions to dictate otherwise. Unacceptable! - At a minimum I should have had dispatch add ONT as an alternate.


Second narrative: Enroute to Palm Springs we were informed that Palm Springs was in a situation of 'airspace saturation'. We were given a hold clearance and an EFC time. The flight was planned without an alternate airport and some hold fuel. I was the pilot monitoring so I asked ATC to clarify what they meant by airspace saturation and give us a better idea of why we were holding. We were told aircraft were not getting in to the airport due to weather. After looking at the situation and calculating our options based on the fuel we had; we asked dispatch to add Ontario as an alternate airport and send us recalculated fuel. We did not get a reply from dispatch before we decided the situation warranted starting the diversion to Ontario. As Ontario was not on the flight plan or fuel calculation as an alternate we decided in an abundance of caution to divert to Ontario. Soon after the diversion was started we received updated fuel information from dispatch. We flew to Ontario and landed with sufficient fuel; the flight was uneventful.


Synopsis: B737 flight crew reported diverting to a nearby alternate when the weather at destination started to cause missed approaches. The forecast at departure did not require an alternate.