B737-800
Flight Crew Air Transport Pilot (ATP)
Inflight Event / Encounter Fuel Issue; Inflight Event / Encounter Weather / Turbulence
Air Traffic Control Issued New Clearance; Flight Crew Diverted; Flight Crew Landed in Emergency Condition; General Declared Emergency
Procedure; Weather
Before leaving I called dispatch to add fuel (800 pounds) because I felt we did not have enough as planned. On the arrival from the east; we were given a reroute to fly backwards and fly a new arrival from the north. Then on that arrival we were given another reroute to an arrival from the west. We knew we could not do this without being very short on fuel. When ATC said we would be issued holding we told them we would have to divert. ZZZ was chosen because from our position we could not make our alternate; without being on empty. We declared an emergency with ATC and landed with 3.5 total; or 1.7 per side. Low level lights were on. At gate with 3.2.
While enroute the weather closed our arrival. We were turned to a VOR which was behind us. We were then assigned another arrival which we started. The new arrival was then closed due to weather and another arrival was issued. We calculated our fuel and determined that we were good for now. We were then told to expect holding; at that time we determined that ZZZ was our best option. We asked for priority handling but while enroute the low fuel lights illuminated so an emergency was declared. We landed without incident.
B737-800 flight crew reports being vectored off the cleared arrival from the east due to weather; and sent north for a north arrival. When this arrival is also closed down by weather the crew is vectored for a west arrival and issued holding instructions. The crew elects to divert to an unplanned alternate at this point and declares an emergency when the low fuel lights come on; landing with 3;500 pounds of fuel.