Synopsis
A large-scale low above the south of Norway slowly travels south-east of Sweden. With a west to northwest current, maritime polar air is brought in. The associated cold front moves south across our country and soon leaves the south. The current becomes colder after cold front passage northwest and the (top) air gradually becomes colder. Friday, a twisted occlusion that lies more or less parallel to the current slowly from north to south across the country.

Model assessment
Attention will be the convective winter rainfall that we will face in the next few days. Initially there are more or less loose showers. As a result of a longer fetch and coastal convergence, the showers begin to focus in lines. The preferred position for these lines slowly moves south. The accumulation of snow in both EC and Harmony exports is probably too fast and too large. The air is gradually getting colder and tomorrow the snow fraction is increasing further inland in particular. Eventually, snow accumulation can occur in more and more places. Probably it stays at 2-5 cm, but locally that can be more (5-10 cm) and depending on time and place where this occurs can cause problems. Another focus is the possible smoothness by freezing. Especially later tonight and tomorrow morning (early) this can occur in the southeast. Smoothness model gives a clear indication.Attention

Wind
Harmony exports are useful over the sea. Later today and next night, the Wadden area and also the coast of NH have a fairly high chance (60-80%). Ha43 is often too high, but a warning has been issued.

View
In winter rainfall poor visibility.

Temperature
In clearances, it freezes inland, in the southeast, and is likely to produce road temperatures below zero and there is a risk of freezing.

Cloud
Near the cold front still some St. Further near and north of the cold front convective cloud. Friday at the occlusion possible low Sc, in snow there is soon St in the Harmony export, this is only realistic with a stable border layer further inland.

Precipitation
And by the cold front rain, which gradually gushes. North of the cold front from Thursday evening rising winter fraction, NESO export of Harmony is a good guide, there is also a chance of thunderstorm, probably especially on the northwest and north coast. Accumulation of snow is likely to be less (approximately 1/3 to half) of that in Harmony exports, with uncertainty about the exact location of most snow. See further model export assessment. There is a considerable amount of precipitation until Saturday morning, with the exception of the southeast 10-20 mm, locally more under showers.

Synopsis
We are under the influence of a large-scale steering low pressure area over Scandinavia and the Baltic Sea region. On the Atlantic Ocean lies a dipole blockade with the axis along 25 °W. Around January 6th the dipole blockade is demolished, it moves high to the Azores and there is a back over Western Europe east or south east. Afterwards, low pressure areas over the eastern Atlantic draw southeast, later east. In many members there is a large-scale high-trail over Western and Central Europe with a large steering low-pressure area over Scandinavia and the North Sea region. The centre of gravity of this layer slowly moves westwards, making the current above the eastern Atlantic western. The distribution between the individual members is wide.

Model assessment and uncertainties
Until about 6 January, the large-scale flow pattern is unambiguous. We are in cold maritime polar air with winter showers. There is considerable uncertainty about where the most precipitation falls. Partly due to small-scale disturbances (troggen, polar lows) that travel south- and south-east of the North Sea on the western flank of the layer, partly because of the uncertainty in the location of storms (downstream of coastal convergence). Until 5 January there is a significant (about 80%) chance of snow (i.e. 3 cm or more/eating), but the uncertainty where and when most snow falls is high. Snow remains too easy in the EC model, but as the wet bulb temperature is usually below 1 °C inland, it is likely that snow remains at some intensity (more than 1 mm liquid equivalent/h), provided there is no negative deviation from the wet bulb temperature in the export. Until 6 January, EC exports are concentrated in the west, with an accumulation of more than 30 cm. This doesn't seem realistic. Realistic seems to be an accumulation of 5-10 cm, locally even more (under active storms). At the coast, precipitation intensity is significantly higher than further inland, so snow can also be significant. The maximum temperature is highly dependent on the strength of the incoming flow component. On the coast it becomes 3-5 °C but inland in low flow the temperature can stay close to zero above a snow layer. There may be a negative bias in the export due to too extensive and too thick a snow layer. The minimum temperature is highly dependent on clearances and wind speed. When the wind falls away during clearances is often too little decoupling in the EC model and it can easily freeze more than 10 degrees above a snow layer. From 6 January, predictability is low. The general trend is towards a north-west, later western flow, but the distribution in the location of the individual pressure systems is large. After the passage of the back around 7 January there is a significant low pressure influence. When low pressure regions south of the Netherlands move east or south east we are in cold air so that snow remains possible. The chance of snow of significance is steadily decreasing after 5 January, to about 10% after 10 January. The temperature distribution remains on the cold side after January 6. There may be a (strong) negative bias due to the too slow melting of a (too thick) snow layer in the EC model. About 30% of the members remain cold. The EC3112 Oper export belongs to the warmest members.

Multi-day Summary
Changing clouds with first winter showers. The snow stays in several places. Light, locally moderate frost at night. During the day, the temperature in most places is a few degrees above zero, where it is clearly less cold on the coast than in the east and southeast.

EPS Period Summary
Large (70%) chance of transition to variable and less cold weather. First possible snow. 30% chance of persistent winter conditions.

Valid from Saturday 03 January to Thursday 15 January