Synopsis
A low-pressure area on the southwest coast of Norway (called 'Enol' by Meteo France) travels south-east of Germany during the day along the Norwegian and Danish coasts, where it arrives Monday morning. The current is western and carries maritime polar air. A first high trench (T500 around -36°C) passes in the morning, a second later Sunday afternoon and at the beginning of the evening. A twisted occlusion reaches the northwest coast mid-Sunday evening and moves southeast over our country in the night, then the current turns northwest. A back that is now still above the Atlantic reaches the British Islands in the night to Monday and reaches our country later on Monday evening and the night to Tuesday. After passage of the back on Tuesday morning follows an inactive heat front that reaches the west of the FIR Tuesday morning.

Model assessment
On approach to the coldest upper airs there are showers today where EC, to a lesser extent Ha43, gives a signal in the NESO for wet snow. EC even calculates a snow cover on this. This image is unrealistic since it will be mostly grain hail, wet bulb temperature at least 2 to 3°C. At most some wet snow falls in the Limburg hills. The main focus is the wind. Sunday at the showers there is a chance of wind blows of 80 km/h. These are mainly above sea and on the coast. This signal does not meet the yellow criteria (more than 90 km/h on the coast). Sunday night and Monday night there is more wind. Remarkable difference is that Ha43 calculates a small layer (or a deeper trough) so that the wind field also arrives a few hours earlier compared to EC. This consequently indicates that there is still uncertainty in the wind field over this period. At present, the northern coastal provinces including the Wadden Sea and the IJsselmeer have a yellow code. Due to the small-scale layer, Ha43 also shows the code yellow criteria in the southern coastal provinces, but this scenario is not the case for the time being.Issues

Wind
Little difference to Sunday night in the models. Actually, there's a 6-7 Bft that will gradually increase to an 8 Bft. In the evening and night to Monday there are differences between Ha43 and EC due to the formation of a small layer (or deeper trough) in Ha43, see model assessment. There are then heavy winds possible in the northern coastal provinces around 80 km/h, on the coast 80-100 km/h. As of Monday morning, the winds are decreasing by approach from the back of the west.

Visibility
Good. Precipitationally decreasing visual conditions to moderate to poor.

Temperature
No smoothness is expected due to the showers with grain hail, as the temperatures of the ground remain well above freezing.

Cloud
Convective cloud with CBs. Top altitude is between FL120-150 and increases to FL200-250 on approach from the altitude trench. At the twisted occlusion a mixture of stratiform and convective cloud. Afterwards the top height quickly decreases to about FL100. Tuesday morning at the heat front in the west of the FIR stratiform clouds with an increasing risk of ST.

Precipitation
Sunday and Monday showers. With the increase of the top altitude temporarily increases the chance of grain hail and thunderstorm. CAPE is 400-700 J/kg above land and above sea 700-1000 J/kg, the effective shear is not too high and is between 10-15 kt. There is a small signal for wet snow in the NESO what we expect in the Limburg hills, see model assessment. As a result of the shadows of England, showers in the north are greatest on Sunday during the day.

Synoptic development
On Tuesday, a watered-down frontal system passes before the Azores goes high to the mainland. The remaining part of the year lies at the centre of the high pressure area above Central Europe or Eastern Europe. Also in the upper air we see a strong ridge above Western Europe. From the turn of the year onwards we see a tilting point where the preference lies more for a (mutual) zonal current where fronts can touch our country.

Model assessment and uncertainties
Until the end of the year, our country has to do with a blocked flow pattern that depends on where the center of the high. Initially, there is maritime tropical air, but after that there is a large spread in which air type we end up. Compared to the 12 UTC ensemble of 21 December we see more members who prefer a colder weather type from Saturday 28 December. Until 28 December it is cloudy and there is little daily course. In half of the members, the center of the high pressure area is close to our surroundings, giving us a cloudy weather picture and little daily movement. In the other half of the members we see a scenario where there is a cleared weather with 20 to 30% chance of light frost in the night. One remark is that during the night and early morning there is little wind there is a real chance of formation of fog. From the turn of the year we see a sharp increase in the precipitation signal and there is also more wind. There will then be a preference for a (mutual) zonal flow that allows low pressure areas and fronts to reach our environment again.

Multi-day Summary
A dry and cloudy weather, from Friday it may also be more sunny area with a risk of fog in the night and in the morning. There's not much wind. Temperatures are around or slightly above the long-term average.

EPS Period Summary
Dry and a reasonable chance (50%) on light night frost. From the turn of the year a great chance (70%) on a variable weather type. Temperatures are around the long-term average.

Valid from Tuesday 24 December to Sunday 05 January