C402 PLT ENCOUNTERS SEVERE ICING CONDITIONS; DECLARES EMER; DIVERTS.

Narrative

THE FLT WAS AN IFR PLANNED FLT FROM ABQ TO KMILL AT NIGHT. THERE WAS A LOW PRESSURE SYS IN SOUTHERN NEVADA; AND THOUGH SHOWERS AND TSTMS MOVED THROUGH THE AREA THROUGHOUT THE DAY; NO ICING WAS RPTED OR FORECASTED ON THE RTE. AFTER DEPARTING ABQ; VECTORS WERE GIVEN FOR THE CLB TO 13000 FT MSL FOR THE MEA TO THE LVS VORTAC. UPON REACHING 13000 FT MSL; AND PRIOR TO LVS; THE ACFT WAS FLYING IN AND OUT OF A SCATTERED LAYER OF CLOUDS WITH NO ACCUMULATION OF ICE. SOON; THE ACFT PENETRATED AN UNSTABLE AREA OF AIR WITH MODERATE TURB; THEN SOME LIGHT RIME. WITHIN 30 SECONDS; THE ICING TURNED TO CLR WITH SEVERE ACCUMULATIONS. ALL DEICING EQUIP WAS ACTIVATED; AND AN IMMEDIATE 180 DEG TURN WAS REQUESTED TO ATC. AFTER I RECEIVED THE CLRNC FOR THE 180 DEG TURN; ATC ASKED IF THE SIT WAS AN EMER; TO WHICH I RESPONDED 'NOT YET.' ABOUT 1/2 WAY THROUGH THE TURN; I DECLARED AN EMER AND AN ALT BLOCK BECAUSE OF THE TURB AND ICING. ALSO; I REQUESTED A LOWER ALT; BUT I WAS TOLD NO LOWER THAN 12500 FT MSL. SOON THEREAFTER; I WAS CLRED TO 11000 FT MSL; THEN 9000 FT MSL AS MEA'S PERMITTED. UPON REACHING 9000 FT MSL; CONDITIONS BECAME VMC WITH LIGHT RAIN AND ABOVE FREEZING TEMP. ATC WAS NOTIFIED THAT THE SIT WAS NO LONGER AN EMER AND AN UNEVENTFUL LNDG WAS ACCOMPLISHED AT SAF. NO REGS WERE BROKEN THROUGH THE FLT. THIS EVENT PORTRAYS THE IMPORTANCE OF APPLYING THE 1-2-3 STRIKES RULE PRIOR TO EACH FLT; IE; NIGHT FLT (STRIKE 1); IMC (STRIKE 2); MOUNTAINS (STRIKE 3). THE FLT SHOULD NOT HAVE COMMENCED.