Narrative:

I am a cfii and was on a training flight with an instrument student last night. We departed ZZZ1 at approximately XA30 pm local on an ADIZ flight plan in VFR conditions. My student had already received a WX briefing and filed the flight plan; as he usually does; when I arrived at the airplane. The plan was to fly the ILS into ZZZ; located 17 mi northwest; then return to ZZZ1. I thought about filing an IFR flight plan; but I wanted more flexibility to let my student; who recently began instrument training; make some mistakes since this would be his first time flying the full ILS approach. I have flown this approach many times and am very familiar with the local area. The AWOS at ZZZ1 at departure reported winds 120 degrees/3 KTS; visibility more than 10 mi; few clouds at 3800 ft; temperature 11; dew point 9. The area forecast was for scattered clouds at 3500 ft. We were going to be flying into higher than 3000 ft MSL (or 2200-2700 ft AGL; given the average terrain elevations in the area). After departing ZZZ1; climbing to 3000 ft and checking in with approach; we listened to the AWOS at ZZZ. The winds were calm with a ceiling of 3200 ft overcast and temperature/dew point at 13/10. We then cleared the ADIZ to the north and were let go by approach to squawk VFR and contact CTAF at ZZZ. About 5 mi south of the IAP for the ILS at ZZZ I asked the student to descend to 2800 ft; the altitude for that transitional segment of the ILS approach. I looked ahead and could see the town and the ZZZ2 beacon clearly. However; when I checked the AWOS at ZZZ3 it reported a ceiling of 1800 ft broken. I knew then something was not right; so I rechked the AWOS at ZZZ and it was still reporting 3200 ft overcast. I instructed the student to lead his turn at the VOR to join the 295 degree radial for the transition. At that moment; the wingtip lights began to shine into visible moisture. I sensed we were on the edge of a cloud layer; but I still had clear visual contact with the city of and the landmark which is a very brightly lit industrial complex located near zzzzz intersection; the point where we'd join the localizer inbound. I was a bit uneasy about the clouds but felt that if we remained at 2800 ft we would pass clear of whatever was out there. Then; about 5 mi from zzzzz; we entered the base of a cloud. I had no forward and minimal lateral visibility but I still had ground contact. At that point I felt the most important thing was to remain calm and keep my student focused on flying the approach. I told the student that we had skimmed a cloud and asked him to descend to 2500 ft; which I knew was below the MSA but based on my local area knowledge of flying around here for the last 5 yrs; I was confident there were no obstructions. We joined the localizer at 2500 ft still hugging the cloud bases with visual ground contact. We were about to begin a descent on the GS so I thought this uncomfortable situation would be over very soon. However; as we flew inbound on the localizer waiting to intercept the GS; I lost ground contact. I rechked the AWOS at ZZZ and it still reported 2800 ft. We were at that point about 2 mi from the FAF; according to the GPS. I had been monitoring CTAF and approach and did not hear any other aircraft; but knew it was not a safe situation. I then contacted approach on our last frequency and asked for an IFR clearance to ZZZ and was told to contact approach on the correct frequency in that area. At that moment we emerged from the cloud at about 2200 ft MSL and saw the runway. We made a full stop landing; and filed an IFR flight plan for an immediate return to ZZZ1. The AWOS at our time of departure from ZZZ still reported 2800 ft overcast (bases at about 3100 ft MSL) and visibility 10 mi. The return flight was uneventful; with IMC between 2500-3000 ft MSL. I learned a few lessons last night. First; never depart at night for a local flight under VFR with reported or forecast clouds so low. I've always told myself and my students to be very wary of clouds at night because you can't see them; and for some reason I didn't follow my own advice last night. The best choice would have been to file IFR out of ZZZ1. The cloud encounter would have been a non-event; and I couldhave easily corrected any altitude or heading transgressions made by my student. I realized afterward that I should have contacted approach for an IFR clearance as soon as I discovered the lower bases while I was still in VMC. (I could not have turned around and returned to ZZZ1 without contacting approach first; due to the ADIZ.) I hesitated and ended up scud running with a student. I read aviation safety; IFR and other journals regularly and consider myself to be one of the more conservative; safer pilots around. But this experience was very humbling and I vow to never repeat it.

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Original NASA ASRS Text

Title: A C172 CFI AND STUDENT APCHED ZZZ IMC WHILE UNDER VFR. WX BRIEF FORECAST VFR; BUT WHEN IMC ENCOUNTERED FLT CONTINUED ON ILS. IFR FILED ON GND FOR RETURN.

Narrative: I AM A CFII AND WAS ON A TRAINING FLT WITH AN INST STUDENT LAST NIGHT. WE DEPARTED ZZZ1 AT APPROX XA30 PM LCL ON AN ADIZ FLT PLAN IN VFR CONDITIONS. MY STUDENT HAD ALREADY RECEIVED A WX BRIEFING AND FILED THE FLT PLAN; AS HE USUALLY DOES; WHEN I ARRIVED AT THE AIRPLANE. THE PLAN WAS TO FLY THE ILS INTO ZZZ; LOCATED 17 MI NW; THEN RETURN TO ZZZ1. I THOUGHT ABOUT FILING AN IFR FLT PLAN; BUT I WANTED MORE FLEXIBILITY TO LET MY STUDENT; WHO RECENTLY BEGAN INST TRAINING; MAKE SOME MISTAKES SINCE THIS WOULD BE HIS FIRST TIME FLYING THE FULL ILS APCH. I HAVE FLOWN THIS APCH MANY TIMES AND AM VERY FAMILIAR WITH THE LCL AREA. THE AWOS AT ZZZ1 AT DEP RPTED WINDS 120 DEGS/3 KTS; VISIBILITY MORE THAN 10 MI; FEW CLOUDS AT 3800 FT; TEMP 11; DEW POINT 9. THE AREA FORECAST WAS FOR SCATTERED CLOUDS AT 3500 FT. WE WERE GOING TO BE FLYING INTO HIGHER THAN 3000 FT MSL (OR 2200-2700 FT AGL; GIVEN THE AVERAGE TERRAIN ELEVATIONS IN THE AREA). AFTER DEPARTING ZZZ1; CLBING TO 3000 FT AND CHKING IN WITH APCH; WE LISTENED TO THE AWOS AT ZZZ. THE WINDS WERE CALM WITH A CEILING OF 3200 FT OVCST AND TEMP/DEW POINT AT 13/10. WE THEN CLRED THE ADIZ TO THE N AND WERE LET GO BY APCH TO SQUAWK VFR AND CONTACT CTAF AT ZZZ. ABOUT 5 MI S OF THE IAP FOR THE ILS AT ZZZ I ASKED THE STUDENT TO DSND TO 2800 FT; THE ALT FOR THAT TRANSITIONAL SEGMENT OF THE ILS APCH. I LOOKED AHEAD AND COULD SEE THE TOWN AND THE ZZZ2 BEACON CLRLY. HOWEVER; WHEN I CHKED THE AWOS AT ZZZ3 IT RPTED A CEILING OF 1800 FT BROKEN. I KNEW THEN SOMETHING WAS NOT RIGHT; SO I RECHKED THE AWOS AT ZZZ AND IT WAS STILL RPTING 3200 FT OVCST. I INSTRUCTED THE STUDENT TO LEAD HIS TURN AT THE VOR TO JOIN THE 295 DEG RADIAL FOR THE TRANSITION. AT THAT MOMENT; THE WINGTIP LIGHTS BEGAN TO SHINE INTO VISIBLE MOISTURE. I SENSED WE WERE ON THE EDGE OF A CLOUD LAYER; BUT I STILL HAD CLR VISUAL CONTACT WITH THE CITY OF AND THE LANDMARK WHICH IS A VERY BRIGHTLY LIT INDUSTRIAL COMPLEX LOCATED NEAR ZZZZZ INTXN; THE POINT WHERE WE'D JOIN THE LOC INBOUND. I WAS A BIT UNEASY ABOUT THE CLOUDS BUT FELT THAT IF WE REMAINED AT 2800 FT WE WOULD PASS CLR OF WHATEVER WAS OUT THERE. THEN; ABOUT 5 MI FROM ZZZZZ; WE ENTERED THE BASE OF A CLOUD. I HAD NO FORWARD AND MINIMAL LATERAL VISIBILITY BUT I STILL HAD GND CONTACT. AT THAT POINT I FELT THE MOST IMPORTANT THING WAS TO REMAIN CALM AND KEEP MY STUDENT FOCUSED ON FLYING THE APCH. I TOLD THE STUDENT THAT WE HAD SKIMMED A CLOUD AND ASKED HIM TO DSND TO 2500 FT; WHICH I KNEW WAS BELOW THE MSA BUT BASED ON MY LCL AREA KNOWLEDGE OF FLYING AROUND HERE FOR THE LAST 5 YRS; I WAS CONFIDENT THERE WERE NO OBSTRUCTIONS. WE JOINED THE LOC AT 2500 FT STILL HUGGING THE CLOUD BASES WITH VISUAL GND CONTACT. WE WERE ABOUT TO BEGIN A DSCNT ON THE GS SO I THOUGHT THIS UNCOMFORTABLE SITUATION WOULD BE OVER VERY SOON. HOWEVER; AS WE FLEW INBOUND ON THE LOC WAITING TO INTERCEPT THE GS; I LOST GND CONTACT. I RECHKED THE AWOS AT ZZZ AND IT STILL RPTED 2800 FT. WE WERE AT THAT POINT ABOUT 2 MI FROM THE FAF; ACCORDING TO THE GPS. I HAD BEEN MONITORING CTAF AND APCH AND DID NOT HEAR ANY OTHER ACFT; BUT KNEW IT WAS NOT A SAFE SITUATION. I THEN CONTACTED APCH ON OUR LAST FREQ AND ASKED FOR AN IFR CLRNC TO ZZZ AND WAS TOLD TO CONTACT APCH ON THE CORRECT FREQ IN THAT AREA. AT THAT MOMENT WE EMERGED FROM THE CLOUD AT ABOUT 2200 FT MSL AND SAW THE RWY. WE MADE A FULL STOP LNDG; AND FILED AN IFR FLT PLAN FOR AN IMMEDIATE RETURN TO ZZZ1. THE AWOS AT OUR TIME OF DEP FROM ZZZ STILL RPTED 2800 FT OVCST (BASES AT ABOUT 3100 FT MSL) AND VISIBILITY 10 MI. THE RETURN FLT WAS UNEVENTFUL; WITH IMC BTWN 2500-3000 FT MSL. I LEARNED A FEW LESSONS LAST NIGHT. FIRST; NEVER DEPART AT NIGHT FOR A LCL FLT UNDER VFR WITH RPTED OR FORECAST CLOUDS SO LOW. I'VE ALWAYS TOLD MYSELF AND MY STUDENTS TO BE VERY WARY OF CLOUDS AT NIGHT BECAUSE YOU CAN'T SEE THEM; AND FOR SOME REASON I DIDN'T FOLLOW MY OWN ADVICE LAST NIGHT. THE BEST CHOICE WOULD HAVE BEEN TO FILE IFR OUT OF ZZZ1. THE CLOUD ENCOUNTER WOULD HAVE BEEN A NON-EVENT; AND I COULDHAVE EASILY CORRECTED ANY ALT OR HDG TRANSGRESSIONS MADE BY MY STUDENT. I REALIZED AFTERWARD THAT I SHOULD HAVE CONTACTED APCH FOR AN IFR CLRNC AS SOON AS I DISCOVERED THE LOWER BASES WHILE I WAS STILL IN VMC. (I COULD NOT HAVE TURNED AROUND AND RETURNED TO ZZZ1 WITHOUT CONTACTING APCH FIRST; DUE TO THE ADIZ.) I HESITATED AND ENDED UP SCUD RUNNING WITH A STUDENT. I READ AVIATION SAFETY; IFR AND OTHER JOURNALS REGULARLY AND CONSIDER MYSELF TO BE ONE OF THE MORE CONSERVATIVE; SAFER PLTS AROUND. BUT THIS EXPERIENCE WAS VERY HUMBLING AND I VOW TO NEVER REPEAT IT.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.