LOW FUEL. EMER DECLARED FOR PRIORITY LNDG.

Narrative

NY ARTCC RERTED US SHORTLY AFTER TKOF FROM LGA FROM ORIGINAL ROUTING OVER ETX-PSB; IOW-LBF ETC; TO A MUCH MORE SOUTHERLY RTE OVER EMI-MRB-HVQ-IIU-STL-MKC-DEN. THIS ADDED MI AND MINS TO A RTE ALREADY PLANNED WITH ONLY 2000 LBS OF HOLD FUEL DUE TO TKOF WT RESTRS OUT OF LGA. I CHKED WITH OUR DISPATCHER; GOT A NEW FLT PLAN AND FUEL FORECAST; AND CHKED DEN; COS AND CYS (OUR DEST AND 2 ALTERNATES) WX EVERY 30 MINS DURING OUR FLT. TSTMS MOVED THROUGH DEN 2 HRS BEFORE OUR ARR; COS AND CYS STAYED CLR. IN DEN ARTCC AIRSPACE AT 0020Z; WE BEGAN RECEIVING REQUESTS TO CHANGE ALT; SPD UP; SLOW DOWN; AND FINALLY WE WERE VECTORED 90 DEGS OFF COURSE. SINCE THE HOLD FUEL ORIGINALLY PLANNED WAS USED UP ON THE RERTE; I FELT THAT NO DELAY WAS ACCEPTABLE; AND TOLD DEN ARTCC WE WOULD JUST PROCEED TO OUR ALTERNATE OF COS. AT 0040Z; WHEN WE WERE APPROX 80 NM E OF COS; COS ARPT CLOSED DUE TO HVY TSTMS DIRECTLY OVERHEAD. OUR 2ND ALTERNATE; CYS; WAS FURTHER AWAY THAN DEN (AND WAS EXPERIENCING TSTMS IN THE VICINITY); SO WITH NO OPTIONS LEFT; I DECLARED 'LOW FUEL EMER' AND WE LANDED IN DEN WITH 6400 LBS OF FUEL (WELL ABOVE THE FAR MINIMUMS OF 4000 LBS PLUS 2100 LBS REQUIRED FOR OUR ALTERNATE); BUT HIS COURSE OF ACTION WAS JUSTIFIED; I FELT; BY THE CLOSURE OF OUR FIRST ALTERNATE AND INACCESSIBILITY OF OUR 2ND ALTERNATE.