TRAPPED BY CLOSING IN WX AND LOWERING FREEZING LEVELS; C180 PLT DECLARES EMER TO LAND SAFELY.

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I WAS ON A VFR FLT IN MY C180. CHKED WX AND LOOKED AT THE LATEST RADAR PLOT BEFORE LEAVING. ALTHOUGH MARGINAL IT SEEMED REASONABLE. CEILINGS OF 1500 FT AND VISIBILITY 7-8 MI. I MONITORED THE ZZZ; ZZZ1 AND ZZZ2 AWOS XMISSIONS WHEN I WAS ABLE TO RECEIVE THEM. ALL WERE RPTING CEILING OF 3500 FT AND VISIBILITY OF 10 MI. THE WX BTWN MY POS AND ZZZ2 DEGRADED AND I DIVERTED TO ZZZ3. I WAS APPROX 15 MI FROM ZZZ WHEN THE NEXT AWOS RPT FROM THERE RPTED 3/4 MI VISIBILITY AND LIGHT SNOW. AT THIS POINT I TURNED AROUND AND HEADED BACK TO ZZZ4; BEHIND ME. THIS ALSO WENT TO LESS THAN 1 MI AND LIGHT SNOW. I WAS DOWN TO APPROX 900 FT AGL AT THIS POINT. I THEN DECIDED TO CALL ZZZ APCH FOR A WX UPDATE. SAME VISIBILITY WAS RPTED. I ELECTED TO CONTINUE INTO THE CLASS D AIRSPACE AFTER DECLARING AN EMER. I HAD THE GND IN SIGHT BUT AS IT WAS BECOMING DARK I THOUGHT A LNDG AT THE ZZZ4 ARPT WAS PREFERABLE TO LNDG ON A ROAD/FIELD. THAT WAS A VIABLE OPTION AS I KNOW THE AREA INTIMATELY AND HAD A GPS MOVING MAP; THE ILS AND VOR TUNED AND IDENTED; ETC. I WAS UNABLE TO CLB TO THE MEA'S FOR THAT AREA AS MODERATE ICING WAS RPTED IN THE CLOUDS ABOVE 10000 FT. I BELIEVE THE MEA'S ON THAT SECTION OF THE ENRTE AREA ARE 9000-10000 FT. LOOKING BACK ON THIS EVENT I REALIZE THE WX WAS NOT GOOD ENOUGH TO ATTEMPT THE FLT. IF I WERE IN THE SAME SITUATION AGAIN I WOULD CALL APCH AND ASK FOR A CONTACT APCH. THE EVENT ENDED WELL CONSIDERING HOW I HAD BOXED MYSELF INTO A CORNER. I LANDED IN SNOW WITH THE RWY IN SIGHT AT APPROX 1 MI. IN THE FUTURE I WILL NOT FLY IN SUCH MARGINAL CONDITIONS.