Roller Coaster No 1

After a flat calm blue sky Friday with sub-zero temps from the higher Glens upwards, a low pressure system is marching in, the wind’s already picking up at low levels in the Central Highlands, and blowing a hoolly further North and West. The low is off course complete with the obligatory Friday night warm sector! :(

While the forecast is not good for anyone wanting to get out on Saturday, depending what happens early next week, the situation weatherwise this weekend might longer term be in our favour, at least for the higher parts of CairnGorm which is where the most snow has stuck this week.

Overnight the FL looks to peak about 4500ft (but this could vary depending on exact track), so we’ll get a period of increasingly wet snow preceding a period of rain at most if not all levels before the precipitation gradually turns back to snow. The layer of wet snow, combined with rain will wet and soften the existing snow pack, consolidating it down a bit. A subsequent layer of  wet will be laid down as temps begin to fall and then this freezing up as temperatures gradually fall back during Saturday.

It’s these kind of cycles that are classic base building conditions, it all comes down to the thaw being sufficient to consolidate the snow pack, but short enough to not do too much damage. What comes through the next 24 hours will thus be in better shape to stand up to the coming weeks roller coaster, but we’ll just have to wait and see how much mild and probably more importantly how much rain we get next week.

Sunday looks set to have a Freezing Level between 1500 and 2000ft with a mix of sunny spells and snow showers, but overnight milder air will be sucked in as it gets pushed up and around the area of high pressure to our SW.  We then look set to enter a period of ‘roller coaster’ zonality, the track of the lows will be all important, a bit more to the South and we’ll get re-freezes between the less severe thaws, bit further North and we’ll end up with raging zonality sweeping band of rain after rain across with near double digit Munro level temperatures.

Should we get the latter, we can at least console ourselves that it’s better to have a bout of screaming zonality now than mid Feb.  One last thing, the models have been really struggling with fairly significant ensemble scatter only 2 to 3 days out on some runs, and some of those ensemble members were fairly tasty.  The best solution for Scottish Snowsports isn’t as one might expect long periods of blocked cold conditions, but the Holy Grail of cold Zonality. We managed to get to cool Zonality last winter at times, can we improve up on it?