TXWY EXCURSION BY TAXIING TFC.

Narrative

TAXIING OUT OF EVV WE WERE WAITING ON AN EDCT (EXPECTED DEP CLRNC (WHEELS UP) TIME. I WAS WORKING RADIO WITH EVV GND CTL. CAPT WAS MANEUVERING ACFT VIA TILLER WHEEL. THE CONDITIONS OF THE TXWYS WERE MOSTLY CLR AND DRY WITH THE EDGES OF THE TXWYS AND GRASS COVERED WITH SNOW/ICE. AS THE ACFT WAS IN THE PROCESS OF BEING POSITIONED FOR TKOF ON RWY 04; THE NOSEWHEEL SLID OFF THE TXWY INTO THE GRASS. THE NOSEWHEEL SETTLED INTO THE GRASS A FEW INCHES. THE ACFT WAS TOWED OUT WITH A TUG AFTER THE PAX WERE DEPLANED. NO DAMAGE TO THE ACFT. SUPPLEMENTAL INFO FROM ACN 264556: THE ACFT WAS STOPPED TO HOLD FOR AN EDCT TO DEST. THEN THE ACFT WAS REPOSITIONED SO NOT TO BLOCK THE TXWY. ALL EDGES OF TXWYS HAD 1/4-1/2 INCH OF SNOW AND ICE; WHICH OBSCURED THE EDGES OF ASPHALT AND GRASS. I MANEUVERED THE ACFT IN A HARD L TURN. ONCE THE TURN WAS INITIATED; THE ACFT WAS STOPPED AFTER REALIZING THE TURN COULD NOT BE MADE. THE NOSEWHEEL SLID ONTO THE GRASS ON THE EDGE OF THE TXWY. MANY SMALL ARPTS HAVE POOR DEFINITION OF TXWY EDGES DURING WINTER MONTHS.