Storm force winds
22nd March 2023
Storm force winds were the defining feature of todays trip into the Northern Cairngorms. Conditions can be infernal in Southerly winds as air is squeezed over the plateau and accelerates downslope.
This was certainly the case in Coire Cas where the wind whipped up snow depositing it on the coire floor. At higher elevations most snow seems to be airborne, with only small quantities being deposited as windslab above 900 metres on North to East aspects. In the storm force winds much of this snow will disappear straight into the atmosphere by ablation.
As the wind speed drops a little to become gale force tomorrow, windslab will be more easily deposited in steep wind sheltered locations. Although this is expected to be shallow, limited in extent and therefore avoidable. The avalanche hazard will be low.
Winter has definitely returned however, and the old snowpack is firm and icy in some locations above 900 metres. This has implications for travel on foot or ski as the consequences of getting blown off your feet (or skis) have the potential to be serious.
Thin cover at lower elevations. Bare ground yesterday in the ski area is covered by some moist fresh snow. A transient return to winter at least.
Old (grey) melt-freeze snowpack with overlying fresh snow deposits (white). Very thin here but was observed to form shallow windslab in steep wind sheltered locations.
An interesting picture this! What it might be difficult to see is that the wind direction in this location was left to right, while the prevailing wind generally was right to left. Snow was being blown in the reciprocal direction due to the the local wind affect. This is common in the Cairngorms due to the almost parabolic convexities of the plateau rim which are perfect for creating down draughting air and rotors below the coire rim. Due to the storm force winds today there was little snow deposition at the coire rim, with most observed mid slope on the coire headwall potentially due to these local wind affects. Hence it is often useful for Mountain Rescue Teams (MRT’s) to use orange smoke flares as helicopters come in. Or indeed SAR helicopters to drop them in the absence of other visual references. – MRT’s and UKSAR were out training today hence the tedious link.
A party out braving the winds, moving confidently along the snow fences in Coire Cas.
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