PVT PLT RUNS INTO WX ON HIS XCOUNTRY TO HOUSTON. GETS LOST; USES A MAYDAY CALL FOR AN EMER DIVERSION TO DWH; NEAR HOUSTON. PLT HAD ALLOWED A 3 HR ELAPSED TIME PERIOD FROM WX BRIEFING TO TKOF.

Narrative

I WAS RETURNING TO HOUSTON FROM DALLAS IN MY PERSONAL ACFT. I HAD OBTAINED A WX BRIEFING ABOUT AB00 AM. AT THE END OF THE BRIEFING; I SUMMARIZED THE FORECAST AS 'VFR TO MVFR; FORECAST TO REMAIN SO ALL DAY.' THE BRIEFER AGREED THIS WAS A VALID SUMMARY. I DEPARTED ABOUT AE00 AM. AS I NEARED HOUSTON; CONDITIONS BEGAN TO DETERIORATE. I DSNDED TO REMAIN BELOW THE CLOUDS; AND STARTED CONSIDERING A DIVERSION. PRETTY SOON VISUAL NAV WAS GETTING DIFFICULT. I WAS NO LONGER CERTAIN OF MY POS. I DECIDED TO DIVERT TO IWS. IT WAS RIGHT OFF RTE 290 WHICH I WAS CERTAIN I COULD INTERCEPT BY CHANGING MY COURSE TO 180 DEGS. I WOULD THEN HEAD SE TOWARD THE ARPT; WHICH I HAD BEEN TO RECENTLY AND WAS CONFIDENT I COULD SPOT. I SOON INTERCEPTED A ROAD I BELIEVED WAS RTE 290 AND BEGAN TO FOLLOW IT. BUT I REALIZED I WAS ON A NE; NOT A SE HDG. AT THIS POINT; I KNEW I WAS LOST; AND I HAD LESS THAN 1 HR OF FUEL. I GOT THE MAP OFF THE R SEAT; TO TRY TO ORIENT MYSELF AND FIND THE NEAREST ARPT. WHEN I LOOKED UP; I WAS IN IMC. I IMMEDIATELY CHKED THE GYROS AND FOUND I WAS HDG S; AND IN A 45 DEG BANK. I LEVELED THE WINGS; TURNED TO A HDG OF 360 DEGS; AND FLEW ABOUT 1 MIN; THEN I REALIZED I WASN'T COMING OUT OF IMC. I DIALED IN 121.5 AND BROADCAST A MAYDAY. AS I GOT NO RESPONSE; I ADDED FULL PWR AND BEGAN A CLB. EVENTUALLY I REACHED HOUSTON APCH. I DECLARED AN EMER; VFR INTO IMC AND REQUESTED VECTORS TO VFR OR A NO- GYRO APCH. I WAS VECTORED TO DWH; WHERE I LANDED UNEVENTFULLY. MY FIRST ERROR WAS NOT GETTING AN UPDATED BRIEFING. CONDITIONS HAD DETERIORATED SIGNIFICANTLY IN HOUSTON; BUT WERE UNCHANGED IN DALLAS. A CONTRIBUTING FACTOR WAS MY RADIO -- IT WAS NOT LEGAL TO XMIT ON; SO I COULD NOT GET FLT FOLLOWING ON INFLT WX UPDATES. MY SECOND ERROR WAS WAITING TOO LONG TO DIVERT. I SHOULD HAVE DIVERTED WHEN I HAD TO DSND; OR TURNED AROUND RATHER THAN DSNDING. THE THIRD AND LAST MISTAKE WAS CHOOSING TO DIVERT TO AN ARPT AHEAD; RATHER THAN ONE BEHIND ME WHICH I KNEW WAS VFR.