Date: 201911
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Weather elements / visibility: Rain; Fog; 8
Light: Dusk
Aircraft: Cessna Stationair/Turbo Stationair 6
Operator: Air Taxi
Operating under: Part 135
Flight plan: VFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class G ZZZ
ATC / advisory: Center ZZZ
Reporter organization: Air Taxi
Reporter function: Pilot Flying; Single Pilot
Reporter qualification: Flight Crew Instrument; Flight Crew Flight Instructor; Flight Crew Commercial; Flight Crew Multiengine
Human factors: Distraction; Fatigue; Time Pressure
Anomaly: Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter VFR In IMC
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Became Reoriented
Contributing factors: Human Factors; Weather; Procedure
Primary problem: Weather

Narrative: Weather had been VFR at ZZZ all day; with a ceiling about 3;500 and 8 miles of visibility; in rain. A low stratus layer at about 600 feet was S and SW of ZZZ; across the bay. My company is single engine Part 135; and must maintain glide to the shoreline. We have company routes and procedures in place to do this. I had gone to ZZZ1; on the far side of the bay from ZZZ. The far shoreline near ZZZ1 had a thin; scattered fog layer from 600 feet (MSL and AGL) to approximately 700 feet. It had been there all day; and had not really moved. It was a stable system. ZZZ1 is in class G airspace; and we had a company operational control release to operate in and out of ZZZ1. I was able to get under the fog layer before it started; and maintain glide distance to shore; stayed above minimum legal altitudes from terrain; and maintained legal cloud clearance and distance requirements. I spent approximately 15 minutes in ZZZ1 unloading freight; and I picked up one passenger to return to ZZZ. After takeoff; I stayed at the minimum legal altitude above terrain to make sure I had good cloud clearance. I had to stay right next to the shoreline to maintain glide distance to shore. There is one short over-water hop to make from the shoreline near ZZZ1 to an island at about 800 feet to maintain glide distance to shore. That area had been free of fog when I had gone to ZZZ1. However; now there was a fog layer at 500 feet. in that area. As I approached it; I thought I could see the layer breaking up and ending; because I could see far mountains through the fog. I decided that I could continue. When I thought the layer was ending; about half way to the island; I pulled up to maintain glide distance to shore. However; with the grey fog and the overcast sky above; I misjudged ; and ended up on instruments; going through the layer. The layer was about 100 feet thick; and I was in it for a few seconds. I was not in the vicinity of immediate rising terrain during the IMC encounter. Ultimately; I should have turned back around to ZZZ1. However; it was the last flight of the day; I was fatigued; daylight was about to fade quickly; and I did not want to get stuck in ZZZ1 overnight. In the future I will be on guard; especially near the end of the duty day; to not accept flights where there is a good chance I may not be able to return under good VFR conditions. Additionally; I recommend all VFR operators utilize tools such as synthetic vision for inadvertent IMC encounters. Our Foreflight subscription gives us moving map; synthetic vision; with an attitude heading reference system (AHRS) overlay. These tools offer incredible situational awareness during an IMC encounter.




Synopsis: C206 pilot reported entering IMC while on a VFR flight plan.