A GLASAIR III COLLIDED WITH MOUNTAINOUS TERRAIN AFTER AN INFLIGHT ENCOUNTER WITH KNOWN FORECAST ADVERSE WX CONDITIONS. THE AIRPLANE WAS BEING OPERATED UNDER IFR. THE CFI/PIC STATED TO THE CONTROLLER THAT SHE WAS ENCOUNTERING AIRPLANE CONTROL PROBLEMS. THE CONTROLLER HEARD A COMMENT EMANATING FROM THE AIRPALNE ON THE TRACON FREQUENCY STATING 'LOSING CONTROL OF THE AIRCRAFT' BEFORE RADAR AND RADIO CONTACT WAS LOST. RAIN SHOWERS AND LIGHTNING WERE FORECASTED BY THE WX SERVICE BEFORE THE ACCIDENT. A WITNESS AT THE ACCIDENT SITE REPORTED, HIGH WINDS, RAIN SHOWERS AND LIGHTNING AT TIME OF ACCIDENT. THE AIRPLANE WAS NOT CERTIFIED FOR IFR FLIGHT. THE AIRPLANE'S OWNER'S MANUAL PROHIBITED FLIGHT IN CONDITIONS THAT WOULD EXPOSE THE AIRPLANE TO THE POSSIBILITY OF A LIGHTNING STRIKE. THE NONINSTRUMENT RATED SECOND PILOT WAS SEATED IN THE LEFT SEAT IN FRONT OF THE FLIGHT INSTRUMENTS. THE SECOND PILOT HAD NEVER FLOWN ACTUAL INSTRUMENTS AND HAD ONLY FLOWN 4 HOURS OF SIMULATED INSTRUMENT FLIGHT.