40 years ago we were cleared to take-off with 2-3 inches os snow on the wing.
I know the world has moved on since then but the conditions were above freezing in April and the aircraft had been deiced before the snow fell. We were assured that the snow would come off the wing at 50 kts.
As advertised the snow indeed fell clear at exactly the moment we were told it would. But . . .
We were #10 in a stream of aircraft departing at 30 second intervals. The previous 9 had all dumped their 4000 sq ft of snow at exactly the same point. As we reached 50 kts the snow fell off our wing and we hit a snow wall. There was a definite deceleration before we continued our take-off.
That snow has to go somewhere. And I have also experienced conditions were the deicing fluid wet the wing and froze in place. The moral - don't enter the active with snow on the wing.