5/16 laterals not draining into 3/4"

[Maple River Sugar]

I have about 40 taps on 5 laterals which are connected to 3/4" mainline with about 2% a grade over 400'.

Walking the line today I noticed the drop lines and laterals are not draining, the temps are 39.

Any idea why? The line has worked fine in the past.

[Pdiamond]

I think it was so cloudy today that it really never warmed up to what it was supposed to be at. See what happens tomorrow.