PLT OF AN SMA SINGLE ENG LAND ACFT MADE A PRECAUTIONARY LNDG ON A STATE HWY AFTER BECOMING TRAPPED BY WX.

Narrative

ON OCT/WED/93; WHILE ENRTE FROM ABQ'S DOUBLE EAGLE ARPT TO LGB; I ENCOUNTERED A FAST MOVING STORM 65 MI N OF PHOENIX; AZ. ALL ADVISORIES THAT I HAD RECEIVED PRIOR TO ENTERING THIS AREA; INCLUDING ENRTE ADVISORIES; SAID THAT THE STORM WAS STILL S OF PHOENIX AND WAS NOT EXPECTED IN THE NORTHERN AZ AREA UNTIL LATE THAT AFTERNOON. I BEGAN TO ENCOUNTER SOME HIGH CLOUDS (BASES APPROX 10000 MSL); 40 MI SE OF FLAGSTAFF; AZ; AND STILL HAD 20 MI VISIBILITY. AS I APCHED PRESCOTT; AZ; THE STORM RAPIDLY MOVED IN FROM THE SW AND SE AND THE VISIBILITY DROPPED TO LESS THAN 1 MI; ESSENTIALLY BOXING ME IN A VALLEY. I ATTEMPTED TO GO NE TO FLAGSTAFF; BUT THE CEILING WAS STILL DROPPING AND THE PRECIPITATION INCREASED TO A POINT WHERE I COULD NOT CLB OUT OF THE VALLEY I WAS FLYING ABOVE. IN ADDITION; ALL RADIOS BECAME INOP DUE TO THE INTERFERENCE OF THE ELECTRICAL STORM. GIVEN THESE 2 FACTORS: 1) I WAS UNABLE TO ESTABLISH RADIO CONTACT TO FLY IFR TO AN ALTERNATIVE RTE AND 2) THE MOUNTAIN OBSCURATION WAS IMPOSSIBLE TO NAV WITH THE CEILING DROPPING TO DANGEROUS MINIMUMS; I DECIDED THAT IT WAS IN THE BEST INTEREST OF SAFETY OF MY PAX AND THE FLT TO LAND ON STATE RTE 169; 1/4 MI W OF I-17. HAD I RECEIVED MORE ACCURATE INFO ON SUCH A VIOLENT AND FAST-MOVING STORM; I WOULD HAVE FLOWN N TO FLAGSTAFF TO WAIT OUT THE STORM.