The snow is returning and the soils should be white everywhere in Ile-de-France, this Wednesday morning.
Météo France forecasts the first snowflakes at 10 p.m. this Tuesday evening.
They will arrive from the south of Essonne and Yvelines, then everywhere in the region from 11 p.m.
We expect between 2 cm in the north and up to 7 cm for the southernmost areas, with between 2 and 4 cm possible in the capital.
"Dry and powdery" snow still detail the forecasters of Météo France, which should hold on the ground because of the negative temperatures.
Until - 5 this Wednesday morning!
The cold snap is expected to last for several days.
With, in Ile-de-France, consequences on travel which can quickly become chaotic.
To avoid too many difficulties, we prepare ourselves on the rails and on the roads.
On the roads.
Snow, ice, frost… The cold is the enemy of motorists when it degrades their traffic conditions.
To avoid this, 650 agents work at night on the 1300 km of regional roads and highways, the equivalent of 2500 football fields!
They were therefore on a war footing in recent days.
When the first snowflakes fall, the objective is to have already salted the roads, to prevent the main roads of Ile-de-France from being paralyzed.
As a preventive measure, the N118 is also closed to traffic from 9 p.m. on Tuesday evening.
And school transport will not be provided this Wednesday in Essonne.
The agents of Dirif (Direction des routes d'Ile-de-France) keep an eye on the grain and can be mobilized 24 hours a day. To act, Dirif has 74 machines (snow gritters), which can perform up to 1500 outings. every winter, on six identified circuits.
All this work is done upstream.
On the other hand, afterwards, there is nothing you can do when the snow falls.
"You have to wait until the snow has fallen to remove it", summarizes Alain Monteil, director of roads in Ile-de-France.
Obviously, motorists do not always understand.
It will therefore be necessary to be patient and respect the instructions not to take the road if the Ile-de-France is covered in white.
On buses and subways.
RATP, for its part, has become accustomed to anticipating cold spells.
For buses, the company ensures every day that the roads are passable, by going to make reconnaissance on the ground.
On the metro, RER and tram sides, the trains are also preheated, the networks checked and heated when possible with "traction rails".
As for the overhead or external lines, the trains run all night long to avoid freezing the rails and catenaries.
Night sites can even be canceled to continue running trains and thus keep the catenaries under tension.
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In the Transiliens.
Because the network is much more external than that of the metro, the drop in temperatures and snowfall have a significant impact on the movement of Transiliens and RERs.
It is first of all, the accumulation of snow in the switches which can prevent maneuvers, and therefore block the trains.
"Needle heaters" - a kind of electric cord - are then put into operation or the agents furrow the tracks with torches.
In addition, "with the cold, the steel shrinks and this phenomenon generates the propagation of cracks and can give rise to ruptures of rails", details one at Sncf Réseau.
To avoid these ruptures, the rails are controlled "thanks to special trains, or agents equipped with portable devices".
Finally, in the event of persistent frost, the catenaries are thawed by electrical voltage, the trainsets preheated and kept under tension throughout the night if necessary.
However, as a precaution, traffic could be slowed down on certain lines.
Even stopped, if a tree collapses on the tracks, under the weight of the snow.