This weekend, very attentive to the sky (and to the thermometers)

BarcelonaWe are at the gates of the announced major change in weather. We have experienced the last hours of calm and heat for this time of year, and this weekend the meteorological situation will take a radical turn. It will be from midday and this afternoon when showers and storms will gain ground from south to north in many regions. Sunday will be a gray, rainy, and suddenly colder day. The rain may be heavy and, in some cases, accompanied by torrential downpours that leave significant accumulations in a short time. For this reason, Meteocat has activated an alert for intense rain in many regions, which could leave more than 40 l/m² in just half an hour or more than 90 l/m² in three hours. The warning is red –danger 5 out of 6– in Vallès Oriental, la Selva, and el Maresme.

Some rains and a return to the full autumn atmosphere that will be the result of a combination of factors. The anticyclone will settle in northern Europe and a storm will form in the Mediterranean. All of this will open a corridor of winds coming from central Europe and will facilitate the arrival of a pocket of cold air at high altitude in the north of the Iberian Peninsula. This is a DANA that has been christened with the name of Adam, the first on the official list of DANAs and storms of this season. This will reactivate the instability and will cause thermometers and the snow level to drop.

In addition, the humid maritime winds from a sea that remains quite warm will be reinforced, which may feed the intensity of the precipitation. This is a situation that we will have to follow very closely, since, depending on the final position of all these pieces, the rain will be more or less extensive and intense. Some models maintain the possibility of an easterly storm between Sunday and Monday. We will continue to follow it.

Saturday: rain from the afternoon

Today we will still wake up with quite a calm, sunny, and mild atmosphere, but intervals of clouds will increase as the hours pass. From midday and during the early afternoon hours, showers and storms will appear and gain ground in the Pyrenees, the Pre-Pyrenees, and Girona. Throughout the afternoon and evening, the precipitation will spread to the Barcelona regions, and towards late afternoon to more places, especially the coast and pre-coast of Tarragona.

Rain that can be intense and locally leave some torrential downpours that accumulate a lot of water in a few minutes or hours. In fact, Meteocat has issued a warning for accumulations exceeding 90 mm in three hours, with high danger between the regions of Garraf and La Selva, including the two Vallesos. In the afternoon they will be more likely in the northeast, and from the evening on, the main event will move to the coast and pre-coast of Barcelona and nearby areas, such as Central Catalonia. There are many alerts activated. Caution must be taken especially in flood-prone areas and near rivers and streams, which can rise suddenly.

Temperatures will gradually drop throughout the day, and many lows may be recorded late in the day. Even so, most highs will still range between 20 °C and 25 °C, higher in the Ebro valley and in Ponent. The tramontane wind will strengthen on the Costa Brava, with increasingly rough sea conditions.

Sunday: gray and cold day

What we will notice most on Sunday will be a sharp drop in temperatures. The environment will be generally cold, with many highs of only 13 °C to 17 °C, but clearly lower in mountain areas. An atmosphere of advanced autumn suddenly and values below what would be expected for this time of year. The drop in maximums may in some cases be up to 10 degrees compared to days ago.

All this with weather that will continue to be quite unsettled. A gray sky is expected throughout the territory, with a risk of rain anywhere. There is still some uncertainty about the final distribution of precipitation, a classic in these autumn Mediterranean situations. There will be a risk of some downpour repeating, especially between Tarragona and Barcelona, while towards Ponent, the Costa Brava, and the western Pyrenees, rain will be less likely.

Attention to the Valencian Community and the western half of the Balearic Islands, where rains will be heavy and abundant, with a risk of torrential downpours and significant accumulations. AEMET has issued orange and red warnings for the coast of Valencia and Alicante for 24-hour accumulations between 200 and 300 mm. There are also alerts activated for intensity (60 mm in 1 hour).

There will be tramontana in the Empordà and northeasterly wind along much of the coast which will accentuate the feeling of cold, with a very rough sea state.

In the Pyrenees, the snow level will drop to 2,000 m or, locally, below. Therefore, the high peaks of the mountain range may become whitened. Next week the unsettled weather will continue, with a risk of further precipitation and an environment that will remain fully autumnal.