Fohn invades during Christmas week, Santa Claus brings the warmth of the off-season! Changes on New Year’s Eve?


No snowmen this Christmas, but given how mild it will be, you can make up for it by making… Christmas Sandmen on the beach!
Luca Lombroso Luca Lombroso 7 minutes

These days, snow lovers look back with nostalgia on some episodes from recent years. Looking at weather history, we remember how today, in 2009, a heavy snowfall that hit most of the north, associated with freezing air. In 2010, on the 17th of December, the entire north and Tuscany were hit by heavy snowfall, including Florence. Then, in those years, hopes for a white Christmas on the plains that had been missing for too long faded away.

And this year too the hope of the White Lady at Christmas they have now disappeared under a strong pressure high.

Synoptic situation

After days with extraordinary baric values, today the isobar over Italy was 1040 hPa if you look at the barometer, you will find that the pressure is dropping. However this does not lead to a turn towards a depressed circulation, but only that one change in conformation pressure altitude. A mild cold front will pass through on Wednesday without bringing any real air mass change but creating a a significant pressure gradient between the north of the Alps and the Po plain. The configuration will be favorable for Föhn conditions in the north.

It is worth noting the pressure high on the southern edge, a Mediterranean depression that affects Pelagia with bad weather and touches the south of Sicily

Weather today and tomorrow

Wednesday and Thursday little to say about the phenomena: light showers could touch Romagna and Marche. A few short rains are not excluded in the inner Tyrrhenian regions in the south. Thursday showers in the interior of Sardinia. Instead, the aforementioned depression will lead thunderstorms, including heavy rains between Lampedusa and Linosa, flying along the southern coast of Sicily.

for the rest, clear and dry prevails, in the north fog and very polluted air, smog accentuated by a “shallow föhn” phase that causes compression and stagnation. Very mild in the mountains, both in the Alps and in the Apennines Wednesday with temperatures below freezing 3000 m and more, on Thursday a temporary drop in altitude to 0°C, around 2000 m. On Thursday a temporary drop in minimum temperatures, light frosts in the north.

ECMWF Christmas Eve estimates remarkable temperature anomalies for the season: proportional to if it were summer, temperatures would be over 40°C! however, there is uncertainty about the areas the Foehns will actually be able to penetrate.

Will Fohn break out between Friday and Saturday?

Predicting the rupture of the valley floor and the Föhn plain is a considerable prognostic challenge because it depends on various factors. A foehn wind will certainly blow strongly in the alpine valleys on Friday, with abnormal heat. On the Alpine border ridge unacceptable conditions at high altitude with a snow storm brought from the north.

Probably outbreaks of Föhn in many northern cities from late morning to Friday afternoon, p maximum temperatures between 16 and locally 20°C. Where it does not burst, the air is very polluted due to the compression effect.

The föhn will not reach the center, but the weather will still be good changeable, no precipitation except light rain in Sardinia. Temperatures in the valleys at low temperatures just above zero, during the day 14-16°C. In the south it rains along the Tyrrhenian coast, otherwise changeable and rather windy.

Heavy snow in the border areas on Saturday in the central-eastern Alps. Walk 30-40 km south of the border, still Föhn with very mild temperatures in the valleys and strong winds at high altitude.

Be careful, the föhn brings heat, but with an adiabatic gradient the temperature drops significantly with altitude, by 10°C every 1000m: for example, when it’s 15°C at the bottom of a valley, it’s -5°C at 2000m.

In cities in the Po valley, sunny and also clear, with a significant temperature range between nights with Tmin close to zero and a day with highs still absurd for the season, between 14 and 18 °C, excluding locally 20 °C.

Mostly clear or partly clear in the center, a strong wind blew in Sardinia. In the south, it rains a little more along the Tyrrhenian regions with a strong westerly wind. Short rains also in eastern Tyrrhenian Sicily.

What kind of weather does Santa Claus find?

Santa Claus’ sleigh will have to overcome the raging jet stream which borders the Alps in the direction from NW to SE, but alson Italy will find mostly stable and even very mild weather conditions enough for the season that he might suffer from the heat in costume.

In short, there was nothing to report on the 24th, 25th and 26th of December, dry almost everywhere, mostly clear in the north, increasing fog and mist appear, but it should not be persistent yet. Good weather also in the center and in Sardinia, albeit with a few more clouds. Small exceptions of short rain still in the south on the Tyrrhenian slopes.

Lower temperatures than previous days, Fohn stops, but still above average especially in heights in the north and in the mountains.

Breakthrough on New Year’s Eve?

No significant changes even in the last days of 2023, but Atlantic disturbances could reappear around New Year’s Eve. So far they appear to be weak or mild systems and always accompanied by mild air, but which between December 31 and the first days of 2024 could bring clouds and some precipitation. However, uncontrolled and unreliable rumors about the outbreak of cold and snow must be denied. As usual, stay tuned for more details on this trend, and from now on, Merry Christmas!


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