MD80 CREW DIVERTS IN VFR CONDITIONS TO NEARBY ALTERNATE DUE TO MICRO BURST ALERTS AT DESTINATION AND LOW FUEL.

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WE LEFT WITH A BASICALLY CLR FORECAST FOR ZZZ AND NO ALTERNATE. AFTER TKOF; THE ACARS FAILED; AND WE NOTIFIED DISPATCH VIA RADIO OF THE ACARS FAILURE AND PROVIDED OUR OUT/OFF TIMES. SHORTLY BEFORE DSCNT INTO ZZZ; DISPATCH ADVISED US OF A JUST-REVISED FORECAST FOR ZZZ SHOWING THE POSSIBILITY OF SOME SMALL BUILDUPS. ATC INITIALLY INFORMED US OF A SMALL BUILDUP SE OF THE FIELD; THEN LATER SAID THE NEAREST BUILDUP WAS 15 MI AWAY. AN APCH WAS BEGUN TO ZZZ; AND ON FINAL WE RECEIVED NOTICE OF SOME WINDSHEAR RPTS; SHORTLY FOLLOWED BY A MICROBURST ALERT WITH A 40 KT LOSS OVER THE RWY. A GAR WAS ACCOMPLISHED DUE TO THIS ALERT. SINCE WE HAD INITIALLY DISPATCHED WITH NO ALTERNATE FUEL; I COULD SEE THAT WE MIGHT END UP LNDG CLOSE TO OUR RESERVE FUEL; SO AS A PRECAUTION I DECLARED AN EMER FOR FUEL AND DIVERTED TO NEARBY ZZZ2. AN UNEVENTFUL VISUAL APCH AND LNDG WERE ACCOMPLISHED AT ZZZ2 AND THE EMER WAS TERMINATED ON TAXI-IN. AS ZZZ2 IS NOT A REGULAR STATION; A BRIEF DELAY WAS ENCOUNTERED WHILE LOCATING ALL NECESSARY FLT FORMS AND PUBS. AFTER CONSULTING WITH DISPATCH; LOADS; DUTY CHIEF; AND LCL CONTRACT MAINT; ALL NECESSARY FLT FORMS AND PUBS WERE LOCATED AND AN MEL ITEM WAS ADDRESSED. WE THEN UNEVENTFULLY DEPARTED ZZZ2 FOR ZZZ. WE LANDED IN ZZZ2 ABOVE RESERVE FUEL; BUT I FELT THE DECLARATION OF EMER AND DIVERSION TO ZZZ2 WAS APPROPRIATE AT THE TIME DUE TO THE UNCERTAINTY OF THE RAPIDLY CHANGING AND UNFORECAST WX; LACK OF ACARS INFO; AND THE SHORT TIME IN WHICH TO MAKE DECISIONS AND LAND THE ACFT.