ALTDEV ALT EXCURSION WHEN MLG EXPERIENCES AN INFLT ENCOUNTER WITH MODERATE TO SEVERE TURB.

Narrative

AFTER 5-10 MINS LEVEL AT FL290 WE TOOK A HDOF TO ZJX. JUST AT THAT TIME WE ENCOUNTER SEVERAL SEVERE UPDRAFTS WITH A 3000 FPM CLB ON THE VSI. I CALLED FOR IGNITION OVERRIDE; KICKED OFF THE AUTOPLT AND KEPT THE WINGS LEVEL. I WAS RELATIVELY HVY AND MY MAIN CONCERN WAS NOT TO STALL OR EXCEED THE 1-G NEGATIVE LOAD LIMITATION BY PUSHING THE NOSE OVER TO HOLD ALT. IT WAS HARD TO KEEP FOCUSED ON THE INSTS. ATTITUDE AND AIRSPD WERE MY PRIMARY CONCERNS; ALT WAS SECONDARY. AFTER A MIN OR SO OF 'RIDING THE WAVES' I GOT BACK DOWN TO FL290. I RPTED THE DEV ASAP AND THE MODERATE TO SEVERE TURB. I REQUESTED A HIGHER ALT WHICH WAS DENIED OR A HIGHER ALT WITH A TURN WHICH WAS ALSO DENIED. AFTER MAKING THE PIREP; AN ACFT OUT AHEAD OF ME RPTED THE SAME CONDITIONS AFTER THE FACT. ALSO; N OF CRAIG; ZJX GAVE ME INFO ON NUMEROUS SIGMETS -- AFTER THE FACT. NONE OF THIS WAS AVAILABLE TO ME. IF I HAD RECEIVED A RIDE RPT OF SEVERE TURB AT FL290 WHICH WAS EXPERIENCED BY AN ACFT AHEAD OF ME I WOULD HAVE REQUESTED A RTE OR LOWER ALT CHANGE TO AVOID IT. FORTUNATELY; I HAD THE FLT ATTENDANTS AND PAX IN THEIR SEATS AND NO INJURIES WERE RPTED. THIS DEV WAS NOT A RESULT OF MISSING A LEVEL OFF.