DURING CRUISE FLIGHT, THE PILOT DIVERTED COURSE TO AVOID SNOW SHOWERS. THE PILOT WAS UNABLE TO STAY CLEAR OF THE SHOWERS AT HIS PRESENT ALTITUDE AND OPTED TO DESCEND. DURING THE DESCENT, THE PILOT APPLIED CARB HEAT AFTER HE NOTICED A DROP IN THE EGT. THE ENGINE LOST POWER SHORTLY THEREAFTER. THE PILOT WAS UNABLE TO REGAIN FULL POWER AND A FORCED LANDING WAS MADE WITH THE LANDING GEAR RETRACTED. THE CARBURETOR ICING PROBABILITY CHART INDICATES ICING AT GLIDE AND CRUISE POWER.