THE PLT DID NOT OBTAIN A WX BRIEFING, FILE A FLIGHT PLAN OR REFUEL THE ACFT PRIOR TO DEPARTING FOR EAGLE COLORADO. THE ACFT DEPARTED AT 1800 UNDER VFR COND. THE PLT REPORTED OVER MINTURN CO AT 2019. WITNESSES AT VAIL CO STATED THAT THE WX COND WERE POOR FROM 2000 TO 2045 WITH HEAVY WET SNOW FALLING AND VISIBILITY OF 100 FT OR LESS. ONE CALLED IT A BLIZZARD. ANOTHER WITNESS SAW A PLANE ABOUT THIS TIME AT LOW ALT JUST OVER THE RIDGE BEING BURRETED BY THE WWND AND LABORING AT HIGH POWER. THERE WERE NO WITNESSES TO THE ACC. ABOUT AN HOUR BEFORE THE ACC THE PLT HAD REQUESTED WX BY RADIO. THE WX THEN WAS REPORTED AS CEILINGS LOWERING WITH MT TOPS OBSCURED, WX DETERIORATING. THE FLT ACKNOWLEDGED THE REPORT AT 1920. HE REQUESTED WX AGAIN AT 2019. THE EAGLE FSS GAVE THE WX FOR EAGLE AND THE PLT ACKNOWLEDGED. THERE WERE NO FURTHER RADIO COMMUNICATIONS WITH THE PLT.