Narrative:

IFR clearance to bjc from 94E at 16000 ft MSL. I had been above cloud deck from abq to cim. At cim I requested and received from denver center FL160. This altitude put me above rising cloud deck. At 43 NM; 358 degree radial from cim I entered clouds at -20 degree celsius. After about 3 mins I flew through an area of moderate mixed/rime icing and requested an immediate deviation right of course. Denver ATC coordination and asked if I wanted higher or lower; requested lower and was permitted to 12000 ft. After 2 to 3 mins and at FL120. I entered area of broken to scattered clouds. I told ATC I could return to V611. At 12000 ft I canceled IFR and proceeded to publication to check WX from publication to bjc. This was flight into inadvertent icing. I fly near the east side of the rockies all year around and have studied the WX in depth. Ice this time of year is always a potential. Although I had checked duats; had checked abq flight watch; had guarded flight watch on communication #2; updated WX conditions at lvs; rtn; tad; publication; I got caught. No PIREPS on icing and icing sigmets were north of publication. Thinking about what I should have done; I might have chosen victor airway from cim - fogle - publication which would gone east of raton pass (lower ground). I believe my icing condition was from an 'up slope;' ie winds from east/southeast causing lift to a wet cloud (orographic lift). Although I did not declare an emergency to ATC... I felt an immediate deviation (right) to lower ground was necessary to get to a non-ice level.

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Original NASA ASRS Text

Title: A C210 AT 16000 FT ENCOUNTERED UNEXPECTED ICING N OF CIM VORTAC AND DESCENDED TO 12000 FT. PLT LANDED BEFORE HIS DEST TO CHK FOR FURTHER ICING CONDITIONS.

Narrative: IFR CLRNC TO BJC FROM 94E AT 16000 FT MSL. I HAD BEEN ABOVE CLOUD DECK FROM ABQ TO CIM. AT CIM I REQUESTED AND RECEIVED FROM DENVER CTR FL160. THIS ALT PUT ME ABOVE RISING CLOUD DECK. AT 43 NM; 358 DEG RADIAL FROM CIM I ENTERED CLOUDS AT -20 DEG CELSIUS. AFTER ABOUT 3 MINS I FLEW THROUGH AN AREA OF MODERATE MIXED/RIME ICING AND REQUESTED AN IMMEDIATE DEV R OF COURSE. DENVER ATC COORD AND ASKED IF I WANTED HIGHER OR LOWER; REQUESTED LOWER AND WAS PERMITTED TO 12000 FT. AFTER 2 TO 3 MINS AND AT FL120. I ENTERED AREA OF BROKEN TO SCATTERED CLOUDS. I TOLD ATC I COULD RETURN TO V611. AT 12000 FT I CANCELED IFR AND PROCEEDED TO PUB TO CHK WX FROM PUB TO BJC. THIS WAS FLT INTO INADVERTENT ICING. I FLY NEAR THE E SIDE OF THE ROCKIES ALL YEAR AROUND AND HAVE STUDIED THE WX IN DEPTH. ICE THIS TIME OF YEAR IS ALWAYS A POTENTIAL. ALTHOUGH I HAD CHKED DUATS; HAD CHKED ABQ FLT WATCH; HAD GUARDED FLT WATCH ON COM #2; UPDATED WX CONDITIONS AT LVS; RTN; TAD; PUB; I GOT CAUGHT. NO PIREPS ON ICING AND ICING SIGMETS WERE N OF PUB. THINKING ABOUT WHAT I SHOULD HAVE DONE; I MIGHT HAVE CHOSEN VICTOR AIRWAY FROM CIM - FOGLE - PUB WHICH WOULD GONE E OF RATON PASS (LOWER GND). I BELIEVE MY ICING CONDITION WAS FROM AN 'UP SLOPE;' IE WINDS FROM E/SE CAUSING LIFT TO A WET CLOUD (OROGRAPHIC LIFT). ALTHOUGH I DID NOT DECLARE AN EMER TO ATC... I FELT AN IMMEDIATE DEV (R) TO LOWER GND WAS NECESSARY TO GET TO A NON-ICE LEVEL.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.