Saturday nights are always the busiest time for opinion polls during an election campaign, because so many of the Sunday papers commission them. We'll get the usual batch of GB-wide polls from Opinium, YouGov, ICM, ComRes, etc, but there's also going to be a full-scale Scottish poll from Survation. I must say I'm just a tad nervous about this one, because it's presumably going to be the most up-to-date Scottish poll we've seen - the last one was Ipsos-Mori, which was conducted between the 22nd and 27th of May. It's perfectly possible that Survation will pick up changes that have happened since then, with the most troubling potential scenario being a significant swing from SNP to Labour as a result of the Corbyn bandwagon.
As I always say, subsamples are our early warning system, albeit we never quite know whether that system is feeding us dud information. There have been a couple of troubling subsamples over the last 24 hours : Ipsos-Mori put the SNP on 34%, Labour on 31% and the Tories on 25%, while a subsample of 18-24 year olds from ICM put Labour way out in front. Both of those results can be explained away without too much effort - Ipsos-Mori's subsample was particularly tiny, and ICM may have just found a very weird sample, because it had Labour in the lead even on 2015 vote recall. All the same, both polls are up-to-date, and are at least consistent with the possibility of a Labour surge at the SNP's expense.
On a more reassuring note, the YouGov projection model has remained relatively stable, and today's update suggests the SNP are on course to win 47 of the 59 seats in Scotland. That's based on interviews over the last seven days, so it covers a slightly longer timescale than most regular polls, but it seems unlikely that the SNP would be as high as 47 if YouGov had picked up a sharp drop in their support over the last few days. However, the floor for the SNP (ie. the minimum number of seats they're expected to win within a 95% confidence interval) has suddenly fallen from the low 30s to the high 20s - and that may well indicate some kind of boost for Labour, even if those votes aren't necessarily coming from the SNP. There's no way the Tories on their own could ever be responsible for getting the SNP below 30.