What was found
IN CRUISE AT ALT OF 32000 THE CAP'S AIRSPEED FAILED & STARTED TO DECREASE FROM 234 KTS TO A LOW OF 150 KTS. AT 150 KTS THE AIRSPEED CLIMBS RAPIDLY BACK TO NORMAL. WE HAD STARTED A DECENT TO 24'000 WHEN THE AIRSPEED RETURNED TO NORMAL. THE ACFT HAD RECENTLY CLIMBED THOUGH MODERATE RAIN & CLOUDS AFTER AIRSPEED RETURNED TO NORMAL. CONTINUED TO WORK NORMALLY FOR THE REMAINDER OF THE FLIGHT. DRAINED WATER FROM PITOT SYS & PERFORMED OPERATIONS CHECK & LEAK CHECK IAW AMM 34-13-00. OPERATIONS CHECKED GOOD. ACFT IS COMPLIANT FOR CONTINUED CAT II OPERATION.