PILATUS PC12 PLT ENCOUNTERS IMC CONDITIONS DURING VFR FLT.

Narrative

THE ENCOUNTER WITH IMC HAPPENED APPROX 3 MINS AFTER A VFR DEP FROM 06C (SCHAUMBERG; REGIONAL). I CLBED TO 1500 FT MSL DUE TO AIRSPACE RESTRS (CLASS B; CHICAGO O'HARE AT 1900 FT MSL) AND TURNED TOWARDS DPA; MY INTENDED LNDG LOCATED 8 MI SW. SHORTLY AFTER TKOF I MADE RADIO CONTACT WITH DPA TWR AND REQUESTED A VFR ARR. TWR INSTRUCTED ME TO FLY W FOR SEQUENCE BEHIND OTHER ACFT. I TURNED W AND NOTICED LOW HANGING CLOUDS. I THEN REQUESTED AN IFR 'POP-UP' CLRNC FROM DPA TWR; INFORMING HIM THAT I WOULD BE UNABLE TO MAINTAIN VFR ON A WESTERLY HDG. TWR GAVE ME A DIFFERENT FREQ FOR THAT REQUEST. I QUICKLY CONTACTED CHICAGO APCH ON THE NEW FREQ AND REQUESTED THE 'POP-UP' IFR. AS APCH WAS GIVING ME A XPONDER CODE I BEGAN ENCOUNTERING IMC. THE IMC WAS IN THE FORM OF LOW HANGING CLOUDS WHICH OCCASIONALLY OBSCURED THE GND. APCH ASKED ME IF I COULD MAINTAIN MY OWN TERRAIN SEPARATION UP TO 2600 FT MSL. I STATED I COULD. I USED GND PROX WARNING SYS (GPWS) TO ENSURE NO OBSTACLES AND CLBED TO 2600 FT MSL. UPON REACHING 2600 FT MSL I XFERRED TO IFR. THE REMAINDER OF THE FLT WAS WITHOUT INCIDENT UNDER IFR. FLT TIME TO DPA WAS APPROX 12 MINS. TIME SPAN ENCOUNTERING IMC BEFORE BEING ON AN IFR CLRNC; LESS THAN 2 MINS.