No offence to any French colleagues! In previous X-Pyr-Races, the French side of the Pyrenees didn’t show off its full potential, but became rather infamous for fog and walking. The big question for Monday: will the clouds disappear? Or will we see another chapter of (assumingly wrong) prejudices about the French Pyrenees?
Let’s elaborate.
Synopsis:
At the surface, the centre of the high-pressure system is moving off to the northeast, which is leading to a gradual decrease in MSLP over the Pyrenees. Meanwhile, at the upper level, a sharp ridge is building over the Bay of Biscay, while the cut-off low over the Med remains stationary. The wind direction is turning from north to east-northeast, which is keeping a northerly component in the lowest layers. The humidity we’re seeing today is stuck in the lowest layers between the French flats and the Pyrenees.
French Basque-Country:
In the morning, the low stratus covering the Basque country is set to extend. The cloud tops are around 1000-1500m, and the cloud base is pretty low.
The clouds should start to break up during the morning (around 1000 LT), turning into 4-6/8 Cu with the cloud base rising from about 900m to about 1500m. The thermal forecasts aren’t great, but they still show decent climbing rates of around 1-2 m/s.
However, it’s worth noting that weather models can struggle to accurately predict low stratus cloud cover, and there’s a common perception that fog in the French Pyrenees is particularly persistent. This could result in a longer-than-expected transition from cloudy conditions to more favourable thermic conditions.
Wind speeds in the boundary layer are currently between 5 and 15 knots from the east, with a more northerly component the closer you are to the Spanish border.
Spanish Basque-Country:
On the Spanish side, the airmass looks drier, but it’s still capped by an inversion at around 2000 MASL, at least in the lower mountains. The thermal forecasts show better climbing rates and a higher cloud base than on the French side, but also more significantly more wind (NE). Once you reach the higher mountains (>2000 MASL), the winds should be weaker in Spain and veer more towards the east in these regions.
Outlook:
It looks like Tuesday will be a good day for flying, with only a little cloud cover. However, the French side seems to be more stable, with only weak climbing rates and probably some wind from the south-west kicking in during the day. The Spanish air seems to be booming, as shown in the XCTherm forecast below.
We’re expecting things to get more complicated again on Wednesday with a trough over Spain leading to stormy and windy weather.
