AN A320 FLT CREW LOST YELLOW HYD SYS IN CRUISE FLT. THEY COORDINATED WITH DISPATCH AND MAINT BEFORE DECIDING TO DECLARE AN EMERGENCY AND DIVERT TO THE NEAREST SUITABLE ARPT.

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HALFWAY THROUGH OUR FLT OVER THE MOUNTAINS; WE WERE ALERTED TO AN ECAM WHICH READ 'YELLOW HYD LOW PRESSURE.' WE FOLLOWED THE ECAM AND NOTED YELLOW QUANTITY WAS NEARLY EMPTY. WE NOTIFIED DISPATCH AND HE CAME BACK WITH DIVERT OPTIONS. I FURTHER REVIEWED HYD IRREGULARS AND HYD SYS IN THE FLT MANUAL TO CLEARLY ASSESS OUR SITUATION. THE ECAM ISOLATED THE YELLOW SYS AND OUR LOSS OF SOME SPOILERS AND OUR YAW DAMPER WAS OUR FLT CTL ISSUE. AFTER ASSESSING OUR DIVERT OPTIONS; WE CHOSE ZZZZ1 BECAUSE OF WX AND FAMILIARITY ON MY PART. DISPATCH GAVE US A RTE AND ATC CLRED US AFTER DECLARING AN EMER. THE CAPT ALERTED THE CREW AND PAX OF OUR PLANS AND SITUATION. WE REVIEWED THE RWY PERFORMANCE AND OVERWT LNDG CHKLIST. DISPATCH ASSISTED US AND ATC WAS CLEAR AND HELPFUL. WE STARTED OUR DSCNT TO THE FIELD. AS WE SLOWED THE ACFT HAD AN UNUSUAL RHYTHMIC SHUDDER THAT FELT LIKE IT WAS THE YAW DAMPER. WE SLOWED EARLY FOR THE APCH AND WAS CLRED FOR THE VOR-DME TO RWY XX ZZZZ1 IN VFR CONDITIONS. WITH LIMITED GND SPOILERS; NO REVERSE THRUST ON THE #2 ENG AND ALTERNATE BRAKES INOP; THE CAPT SET THE ACFT DOWN WITH A 200 FPM DSCNT RATE. THE OVERNIGHT LNDG WAS SMOOTH AND UNEVENTFUL TOUCHING DOWN AT ABOUT THE 1000 FT MARK TO TURN OFF THE RWY AT TXWY X. WE THEN TAXIED TO THE RAMP WITH TWR TO BE MET BY OUR CONTRACT HANDLERS AND MAINT.