Narrative:

We were 48 mins late off the gate due to deicing. We taxied the length of runway 3L and were told to hold short. A discussion about a NOTAM that gave takeoff mins of 300 ft and 1 mi (which was read to us by an off duty pilot) induced me to ask the tower for the prevailing visibility, which was '2 variable to 3 mi in light snow and fog.' we were then instructed to report the passing of a landing widebody transport Y which we did. We were then cleared into position to hold. I never set the brakes as we were 'cleared for takeoff RVR on 3L 3500 ft in blowing snow and fog.' I would see approximately half the length of the runway with good visibility to the sides with the fire house barely visible. I said nothing but gave control of the plane to the copilot for the takeoff after assuring myself of 'local conditions' sufficient to stay on the centerline. I believed the landing widebody transport Y had caused the sudden deterioration. The takeoff was uneventful with improving visibility through out. I was instructed to switch to departure but before I was able to I heard the tower say to landing traffic 'the visibility had dropped to 1600 ft RVR.' my concern is does 'local conditions' override a NOTAM for takeoff mins? The runway was covered with 1/2 inch light snow as we taxied parallel to it. Supplemental information from acn 200113. Do remember visibility being very good as I could see quite far down the runway. In retrospect, I believe the momentary reduced visibility was probably caused by the landing widebody transport Y with reverse thrust kicking up the light snow.

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Original NASA ASRS Text

Title: ACR WDB MADE A TKOF FROM DTW IN WX BELOW NOTAMED MINS BUT WELL ABOVE NORMAL RWY MINS.

Narrative: WE WERE 48 MINS LATE OFF THE GATE DUE TO DEICING. WE TAXIED THE LENGTH OF RWY 3L AND WERE TOLD TO HOLD SHORT. A DISCUSSION ABOUT A NOTAM THAT GAVE TKOF MINS OF 300 FT AND 1 MI (WHICH WAS READ TO US BY AN OFF DUTY PLT) INDUCED ME TO ASK THE TWR FOR THE PREVAILING VISIBILITY, WHICH WAS '2 VARIABLE TO 3 MI IN LIGHT SNOW AND FOG.' WE WERE THEN INSTRUCTED TO RPT THE PASSING OF A LNDG WDB Y WHICH WE DID. WE WERE THEN CLRED INTO POS TO HOLD. I NEVER SET THE BRAKES AS WE WERE 'CLRED FOR TKOF RVR ON 3L 3500 FT IN BLOWING SNOW AND FOG.' I WOULD SEE APPROX HALF THE LENGTH OF THE RWY WITH GOOD VISIBILITY TO THE SIDES WITH THE FIRE HOUSE BARELY VISIBLE. I SAID NOTHING BUT GAVE CTL OF THE PLANE TO THE COPLT FOR THE TKOF AFTER ASSURING MYSELF OF 'LCL CONDITIONS' SUFFICIENT TO STAY ON THE CTRLINE. I BELIEVED THE LNDG WDB Y HAD CAUSED THE SUDDEN DETERIORATION. THE TKOF WAS UNEVENTFUL WITH IMPROVING VISIBILITY THROUGH OUT. I WAS INSTRUCTED TO SWITCH TO DEP BUT BEFORE I WAS ABLE TO I HEARD THE TWR SAY TO LNDG TFC 'THE VISIBILITY HAD DROPPED TO 1600 FT RVR.' MY CONCERN IS DOES 'LCL CONDITIONS' OVERRIDE A NOTAM FOR TKOF MINS? THE RWY WAS COVERED WITH 1/2 INCH LIGHT SNOW AS WE TAXIED PARALLEL TO IT. SUPPLEMENTAL INFO FROM ACN 200113. DO REMEMBER VISIBILITY BEING VERY GOOD AS I COULD SEE QUITE FAR DOWN THE RWY. IN RETROSPECT, I BELIEVE THE MOMENTARY REDUCED VISIBILITY WAS PROBABLY CAUSED BY THE LNDG WDB Y WITH REVERSE THRUST KICKING UP THE LIGHT SNOW.

Data retrieved from NASA's ASRS site as of July 2007 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.