Interesting news item from the BBC about the lingering snow patches in various gullies across the mountains of Scotland. I wonder if the three patches in the Cairngorms will survive? I suppose it will depend on the kind of Autumn that we are in for, cold and dry, or mild and wet. Just across the way from Ben Nevis is Aonach Mor with an AWS on it (WMO #03041). The AWS is not quite at the top of Aonach Mor which is 1221 M high (4,006 feet), but a little way down at the top of the chairlift at 1130 M (3,707 feet), from where I guess there is some kind of extension lead buried under the ground that connects the two. So temperatures should be not far off what they would be on the north face of the Ben, but of course that face would be in perpetual shadow.
OGIMET wouldn’t let me download last Autumn’s data for the AWS on Aonach Mor, but here is the thermograph from the 4th of January through to April (fig 3), and as you can see although it was sub-zero for extensive periods, it wasn’t overly cold, and January was notably mild.
The rainfall anomalies for the period between November 2016 and March 2017 were generally near average, with November being a dry month (fig 4).
Figure 4 – November 2016 – March 2015 rainfall anomalies – Courtesy of the Met Office
The temperatures through the extended winter period where all above average, except for the dry November which was colder than average, December was exceptionally mild (fig 5).
Figure 5 – November 2016 – March 2015 temperature anomalies – Courtesy of the Met Office
Iain Cameron is correct when he says that the demise of the snow in the gullies of Ben Nevis was down to the lack of snow last winter. Snow is obviously dependent on rain falling with temperatures near or below freezing, and the lack of it was down to two things, colder periods also tended to be drier, and the wetter periods were also usually mild, a combination of the two meant that not enough snow fell to fill the gullies to survive through till the following Autumn.
I suppose if you coupled up the temperature from Aonach Mor with daily rainfall totals from Tulloch Bridge you could with a bit of jiggery-pokery estimate how much snow fell and accumulated at a 1000 M. With a few other bits of climate data you could also try to calculate how much snow was lost due to sunshine, evaporation, sublimation, and warm rain. It sounds like the job for a sophisticated NWP climate modelling tool as far as I can see.