Things are set to remain exciting in the weather forecast over the next few days. After a classic "blue at the top, gray at the bottom" Thursday, things will become more dynamic from tomorrow. Various disturbances will reach us from Friday to the middle of next week. The increasingly mild air masses will cause the snow line to rise. This could become a problem, especially in the first half of next week.
So far this fall and winter, we've been largely spared the typical fog and high fog conditions over the Swiss Plateau due to the frequently recurring south-westerly to westerly conditions. However, today's Thursday will show exactly this side. There will be widespread fog or deep high fog over the Swiss Plateau. In the morning, the upper limit will mostly be between 600 and 800 meters, with the upper limit rising slightly during the course of the day to between 800 and 1000 meters. The chances of clearing are likely to be best in the eastern Swiss Plateau and the Lake Constance region, while it will probably remain a gray affair in the central and western Swiss Plateau. The picture is different above and outside the fog/high fog areas. A mostly sunny day awaits us here. In the morning, only a few occasional patches of high clouds will pass through, but the amount of high clouds will gradually increase during the afternoon, without detracting from the friendly impression. After slightly negative temperatures at the start of the day, we expect only slightly positive maxima in the fog and high fog regions during the day. Where the fog and high fog cover can lift, a few more degrees should be possible. At high altitudes, ideal piste conditions will prevail and temperatures will rise significantly over the course of the day. At 2000 meters, temperatures will rise from around –7 degrees in the morning to around 0 degrees by the evening. There is also plenty of sunshine in the south, where temperatures of up to 7 degrees are measured.
Fig. 1: Hörnlihütte at around 2500 meters; Source: Roundshot
Disturbance on Friday
In the coming night, cloud cover will gradually increase from the west ahead of a warm front. The first showers are expected in the western parts of the country towards the morning. Snow will usually only fall from 800 meters, with the snow line rising rapidly towards 1400 meters. In the course of the morning, the precipitation will spread eastwards, with flakes initially falling down to lower altitudes in the central Swiss Plateau, although here too the snow line will quickly rise to between 1200 and 1400 meters. According to some models, some freezing rain is also conceivable in a short time window in the morning, especially in the central Swiss Plateau and towards the northern edge, but this is unlikely to be a widespread event (explanations of freezing rain in the following illustration). Highs will be around 2 to 4 degrees. The weather on the southern side of the Alps will also be partly cloudy with occasional wet weather, especially towards the Alps.
Fig. 2: Regions possibly affected by freezing rain; Source: MeteoNews
Fig. 3: Schematic representation of freezing rain (left) and freezing rain (right); Source: MeteoNews
A mixed second weekend of Advent
After a friendly start to Saturday, the next disturbance zone will reach us from the west in the second half of the day. The snow line will rise from around 1500 meters to around 2000 meters at the beginning, but it will remain much lower in the Alps and in the very east for a long time. During the night to Sunday, the snow line will fall again to around 1200 meters. After the last showers on Sunday morning, the day will be dry for a long time and occasionally quite sunny. However, the next disturbance won't be long in coming, with widespread wet weather expected again on Monday night. Temperatures at the weekend will be between 7 and 10 degrees, with strong south-westerly to westerly winds with gusts of 50 to 70 km/h, especially on Sunday night.
Three women's speed races will take place in St. Moritz from Friday to Sunday. Tomorrow Friday will be mostly cloudy, with some snow falling at times. In principle, however, the super-G should be feasible from a meteorological point of view. For the first downhill on Saturday, the weather is likely to be on the sunny side, with some fresh snow expected in the night to Sunday. During the day, however, it is likely to be dry and increasingly sunny.
Repeated precipitation at the beginning of next week
On the southern edge of a low pressure system over the British Isles, we will enter a brisk, humid and mild westerly flow at the beginning of next week. From Monday to Wednesday, it will be intermittently wet, with large amounts of precipitation in total (see below). Highs will reach 9 to 12 degrees, and there will be moderate, and on Monday sometimes strong, south-westerly winds. With the mild air masses, the snow line on Monday and Tuesday will be in the range of 2000 to 2200 meters, gradually dropping below 1500 meters during the course of Wednesday as the high winds shift to the northwest. The large amounts of precipitation in combination with the high snow line are likely to cause runoff levels to rise significantly and possibly burst their banks. However, it is still too early to make a precise assessment.
The southern side of the Alps, protected by the Alps, will remain favorable, with sunny and dry weather. Highs will reach around 8 degrees.
Fig. 4: Total precipitation amounts until Wednesday evening according to the European model; Source: MeteoNews/UBIMET
Fig. 5: Accumulated precipitation amounts until Wednesday evening according to the American model; Source: MeteoNews/UBIMET
The models clearly show the formation of an atmospheric river with a band of precipitation from the Atlantic to the Alps. This section shows the situation on Monday afternoon.
Fig. 6: Atmospheric river next Monday; Source: MeteoNews/UBIMET
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