Date: 201503
Local time of day: 0601-1200
Location: PRB.Airport, CA
Flight conditions: Mixed
Weather elements / visibility: Fog; 99
Light: Dawn
Aircraft: Premier 1
Operator: Corporate
Operating under: Part 91
Flight plan: None
Mission: Other Reposition
Flight phase: Landing
Reporter organization: Corporate
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Instructor; Flight Crew Multiengine; Flight Crew Instrument
Human factors: Situational Awareness
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Unstabilized Approach; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: In-flight
Result: General None Reported / Taken
Contributing factors: Human Factors; Weather
Primary problem: Human Factors

Narrative: We had a re-position flight in the early am. The weather was reporting 10 miles and clear with a temperature/dew point spread of approximately 3 degrees. The forecast was for few clouds at 100 feet at the time of arrival (20-30 min prior to sunrise). Due to the forecast and my experience with this particular airport; I was concerned about radiation fog developing at sunrise. We departed home-base approximately 15 min early because of this concern. As we approached the airport from the east; approximately 40 miles out; I could see fog to the east and north of the field. I had briefed a landing on runway 19; with a backup landing plan with left traffic to runway 01; if runway 19 was not viable. Upon arrival and approximately 10 miles to the east from the field; I noticed a fog bank that had developed to the east and north of the field and covering the approach end of runway 19. The majority of the airport and runway 01 was clear. Determining that runway 19 was not a viable landing option; I decided to make left traffic and land on runway 01. I informed my copilot and he changed landing approach to a visual 3 mile final for runway 01 in the FMS. As we were configuring to land on downwind; I noticed the fog was steadily creeping over the airport from the north and east. Slowing and configured with flaps 10 and gear down on downwind; abeam the threshold; I noticed low level clouds that were 2-3 miles from the approach end of runway 01. I determined that attempting a 3 mile visual approach; with a normal 3 degree glide-path would put us in the low level clouds. Because of this I turned base early; while still at pattern altitude. At this time; the co-pilot called out; 'high and fast'. I adjusted throttles to idle and attempted to extend speed brakes while descending the aircraft. The speed brakes didn't work and the co-pilot reminded me that it wouldn't work in this configuration. As he said that; I had realized I became momentarily confused with another type aircraft I concurrently operate and fly which allows speed-brakes with flaps and gear extended.  I de-selected the speed-brakes; confirmed throttles at idle. The aircraft was steadily slowing and descending; however because I was closer in due to the low-level clouds to the south; I was still high. Realizing this I called for flaps 30 (full down); and pitched the nose lower to lose altitude more quickly; going beyond 1;000 feet min in momentary descent. The copilot called again; 'high and fast'. I noted that the speed was above ref but below vac and decreasing steadily. With my experience in the aircraft; I realized that I would be over threshold at Vref with the current trend continuing. The fog was rapidly developing over the runway; approaching from the north and now was beginning to cover the 1;000 feet markers. Still having sight of the runway 01 threshold; numbers and lights; I continued to descend at a greater than normal rate so that now I could land on the numbers; instead of the 1;000 feet markers. This activated the GPWS; which I ignored because I had a visual of the surrounding terrain and environment as it was dawn and daylight was increasing. Determining that I was on a proper path approximately 500 - 1000 feet from the threshold; I relaxed the yoke and aimed for the numbers. The aircraft decreased in speed normally; and touched down normally. Upon landing and reaching the 1;000 feet markers; the aircraft was engulfed in fog and visibility reduced to approximately 1/4 mile. Upon reaching a runway exit taxiway; I stopped the aircraft and retrieved my iPad geo-synchronous taxi diagram to help taxi the aircraft to parking. Looking back; I know that because we had no passengers on board; I was willing and able to fly the aircraft beyond our normal scope of operations; in order to make the landing. Otherwise; the steep descent and maneuvering of the aircraft would have made any passenger nervous; and we would have immediately gone to our alternate less than 30 miles away. Also; because I was expecting to see a mile of runway once we landed; I had  that landing visually on the runway numbers in 'VFR' conditions was still safe; because I assumed I was going to maintain 'VFR' under the supposed thin layer. Later; while discussing the situation; my co-pilot and I both stated that we thought the fog layer would have been a very thin film only at about 100'; based upon the airport's current (incorrect) forecast. We didn't think it would be all the way to the ground and as thick as it was; especially since the top layer was only about 100 feet high. The runway is not configured for taxi in low-visibility condition because it has no center-line lighting. My co-pilot was uncomfortable with the unfolding scenario; but elected not to state his position; only calling out 'high and fast'. I told him that; if at any time; he felt uncomfortable he should have stated it and/or called for a go-around. I was busy flying the airplane and maneuvering the aircraft. I didn't have time to look over and analyze his facial and postural expressions.As it was; once the sun rose; the visibility went to less than 1/4 mile and we had to delay departure for an hour because our FOM states that we shall not depart in visibility that is less than 1/4 mile. Another note; the forecast for the airport was completely incorrect; but the conditions were in-line with the localized weather phenomena for that area and should have been expected. I feel that I am a professional pilot and make proper ADM decisions; however; in this case; the right choice would have been not to attempt the approach and immediately fly to the alternate due to the developing conditions. One more break of the link in the chain (like an aircraft departing on runway 19 without talking on the radio - it was an uncontrolled field); and it could have been disastrous since we couldn't see more than 2/3 of the runway.




Synopsis: PRM-1 Captain reported continuing an unstabilized approach to a landing in marginal weather conditions.