PVT PLT OF SMA ACFT INADVERTENTLY TRANSGRESSED A RWY BECAUSE THE RWY MARKINGS WERE OBSCURED BY SNOW.

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IN PREPARATION FOR DEP FROM CLE; AFTER COMPLETING ACFT RUNUP AT THE W END OF TXWY R; I WAS INSTRUCTED TO TAXI TO RWY 23R VIA TXWY V AND RWY 10. WHILE TAXIING ON V; I ASKED IF IT WOULD HELP THEM (ATC) IF I DEPARTED RWY 18 (WIND 150 AT 8). ATC THEN AMENDED THE TAXI INSTRUCTIONS TO TAXI TO RWY 18. CONTINUING THE TAXI TO RWY AND ONTO 10 I TAXIED ON RWY 10 LOOKING FOR RWY 18. AT THIS TIME I TAXIED FORWARD LOOKING FOR 18 AND FINALLY ENDED UP TAXIING ONTO RWY 18. AT THIS TIME I REALIZED I WAS ON THE RWY THAT I WAS ONLY SUPPOSED TO TAXI TO. I IMMEDIATELY DID A 180 AND TAXIED OFF RWY 18. SINCE I WAS WITH GND CTL I SWITCHED TO LCL (TWR) FREQ AND WAS ASKED IF I WAS ON TWR. I RESPONDED I HAD JUST SWITCHED AND GOT CONFUSED ON LOCATION OF RWY 18. I WAS TOLD TO DO A 180 AND TAXI FURTHER BACK ON RWY 10. AN SMT ACFT WAS CLRED TO LAND ON 18 AND LANDED ABOUT 30-60 SECONDS LATER. I CAUSED MY OWN PROB BY NOT NOTICING THE REILS AT THE APCH END OF RWY 18 AND NOT BEING MORE AWARE OF MY POS. CONTRIBUTING FACTORS INCLUDED SNOW ON GND OBSCURING THE RWY 18 MARKINGS AND NO SIGNS ON RWY 10 INDICATING RWY 18 EVEN THOUGH TXWYS AND RWYS 23L/R DO HAVE PROMINENT SIGNS INDICATING THEIR LOCATION.