VFR IN IMC IN CTL ZONE.

Narrative

SOME LIGHT FOG WAS SEEN ON THE W AND E SIDE OF THE FIELD. THIS FOG APPEARED SIMILAR TO FOG SEEN PREVIOUS MORNINGS WHICH WOULD RISE FROM A POND ON THE SW SIDE OF THE FIELD. I TOOK THE ACTIVE RWY 36 FOR DEP. ACCELERATING DOWN THE RWY; I SAW WHAT APPEARED TO BE THIN SHEETS OF FOG A FEW FT ABOVE THE ACFT; AND UPON ROTATION; I SAW THAT I WOULD FLY THROUGH ONE OF THESE 'SHEETS.' HAVING SEEN 'SHEETS' LIKE THESE BEFORE; I WAS NOT DISTRESSED WITH THIS PROSPECT AS I THOUGHT I WOULD BE IN AND OUT IN A TENTH OF A SECOND. AFTER PENETRATING THE FOG SHEET; FORWARD VISIBILITY WAS SEVERELY DECREASED; BUT WHEN IT DID NOT RETURN VERY QUICKLY; I BECAME DISTRESSED. AFTER APPROX 5 SECONDS OF FLYING WITHOUT EMERGING FROM WHAT I THOUGHT WAS A THIN SHEET; I RADIOED BACK TO THE ACFT BEHIND ME WHO HAD RADIOED THAT HE WAS DEPARTING NOT TO TAKE OFF. THE OTHER ACFT DID NOT TKOF. I KNEW THAT I HAD FALLEN INTO THE TRAP OF FOG BEING THIN FROM BELOW BUT VERY DENSE VIEWED EDGE ON. ABOUT 10 SECONDS AFTER DEP; I WAS THROUGH THE FOG AND COULD SEE WHAT I HAD TAKEN OFF INTO. THERE WAS A THIN SPREAD OF FOG FROM ABOUT 2 W OF THE ARPT TO AS FAR AS I COULD SEE E. VISIBILITY ABOVE THE FOG WAS UNRESTRICTED; AND THERE WERE NO CLOUDS ABOVE. AFTER CLRING THE SHEET; I CLBED TO 1400 MSL AND TURNED XWIND. AT APPROX THIS TIME; AN SMT RPTED TO BE AT LUNCH INTXN INBOUND ON THE VOR 13 APCH. I COULD SEE THE SMT AND ON DOWNWIND RPTED THAT I WAS AT 1900 FT AND CIRCLING THE FIELD. I COULD EASILY SEE THE FIELD BELOW; AND THE SMT INBOUND. MY INTENTION WAS TO CIRCLE AND WAIT FOR THE FOG TO BURN OFF. THE SMT PASSED OVER RWY 13 AND THEN CALLED ON THE RADIO TO SAY THAT HE WAS CIRCLING TO RWY 31. THE SMT THEN DEPARTED TO THE NW; TO DO THE APCH AGAIN I ASSUMED. AFTER CIRCLING FOR ABOUT 5 MINS AND BEING ADVISED BY AN INSTRUCTOR ON THE GND THAT THE FOG WOULD JUST GET WORSE; I ENTERED DOWNWIND FOR RWY 36. AFTER TURNING BASE; I IMMEDIATELY SAW THE PAPI LIGHTS. ON FINAL AT ABOUT 500 AGL; I WAS ABLE TO SEE THE BEGINNING OF THE RWY AND THE THRESHOLD MARKINGS. AIMING FOR THE THRESHOLD; THE RWY LIGHTS SOON BECAME VISIBLE FOR ABOUT THE FIRST HALF OF THE RWY. THE THIN AMOUNT OF FOG WAS PENETRATED VERY QUICKLY; AND THE WHOLE LENGTH OF THE RWY BECAME VISIBLE. THE LNDG WAS MADE NORMALLY. I TAXIED AND TIED DOWN; AND RETURNED INSIDE THE TERMINAL. THE PLT OF THE SMT WAS ON THE RADIO AFTER MAKING ANOTHER APCH AND NOT MAKING IT IN. HE WAS REMARKING ABOUT HOW HE COULD NOT LEGALLY MAKE IT INTO THE FIELD. ABOUT 10 MINS AFTER I TOUCHED DOWN; AN SMA LANDED ON RWY 36. THE SMT RETURNED TO KANSAS CITY DOWNTOWN ARPT. THE FOG BECAME MORE DENSE. APPROX 30 MINS LATER; 9K4 HAD 1/4 MI VISIBILITY; AND KANSAS CITY INTL HAD 1000 RVR. FACTORS CONTRIBUTING TO THE ERROR OF TAKING OFF INTO THE FOG WERE: 1) NOT OBTAINING A TEMP DEWPOINT SPREAD FROM WHITEMAN AFB; 2) ASSUMING THE FOG WAS SIMILAR TO FOG SEEN ON PREVIOUS DAYS; 3) NOT HAVING ENCOUNTERED RADIATION FOG AND ITS CHARACTERISTICS. IN THE FUTURE; I WILL BE MUCH MORE CONSCIOUS OF WX ON SUPPOSEDLY 'SEVERE CLR' DAYS. THE FOLLOWING DAY; I WENT OUT TO PRACTICE TOUCH AND GOES; AND THE TEMP/DEWPOINT SPREAD WAS 5 DEGS; BUT THERE WAS A SLIGHT WIND; AND NO FOG FORMED.