The past week has again been mostly dry and quite cold with temperatures in the low -20s up until Friday when milder air pushed in from the SE and lifted temperatures to between -3°c and -5°c through this weekend. Clouds were thick enough today to produce some light snow flurries and with that came along a light breeze from the SE.
Temperatures have largely remained below freezing for many weeks now. The highest temperature in November was early on with 4.8°c while the average November temperature in Bjorli was -7.9°c. The lowest temperature was -27.8°c. December so far has an average monthly temperature of -19.7°c as of today (Dec 10th) with the lowest being -29.7°c. After the less cold weekend, temperatures will briefly become colder again throughout Monday and more especially on Tuesday and Wednesday. However, a big change in weather pattern is on the cards and this change will begin to unfold through Thursday as pressure begins to rise over the UK and the jet stream fires into action to the north.
The above charts clearly show the large Euro High Pressure but the GFS chart shows more of a SW'ly wind. The 850 hPA temperatures are quite high with very mild air coming up from the Azores and over the top of the High Pressure into Scandinavia. Temperatures will therefore begin rising from Wednesday night and continue to rise through the second half of the week, along with a strengthening wind from the SW. Snow flurriers are also expected but precipitation amounts will likely increase as we push into the weekend. The exact details remain very uncertain regarding the timing of the approaching Low Pressure and the orientation of the High Pressure.
The ECM T+144 (above) is also showing a more progressive evolution and is similar to the UKMO but having looked at the GFS Panel charts at the same range, the deep SW'ly wind cannot be discounted.
Milder and unsettled
Both GFS and ECM ensembles are showing high confidence for a change in pattern with the Euro High Pressure expected to bring milder temperatures. Beyond day 6, the trend is also showing the SW wind veer W'ly and then NW'ly but again, there are subtle differences between all models. Some models are showing a very changeable and mobile pattern with variable temperatures across Bjorli and with spells of precipitation while other models are keen in bringing a much colder weather type with a Scandinavian trough and heavy snowfalls. Looking at all the model data, I think it is now quite certain that a milder and unsettled outlook is in store and I'd also go along with the idea that some rain is likely over next weekend. Temperatures are likely to rise to a few degrees above freezing and given the variable weather type and high temperatures at 850 hPA, I think we'll see periods of rain and sleet throughout the weekend and some of it could be heavy. Winds are also likely to increase and we could see some strong gusts at times. Wet snow cannot entirely be ruled out because if the High is slightly further south than expected and the wind is more W'ly, a degree or two lower in temperature can be the difference between rain, sleet and snow.
Beyond next weekend and into the start of the following week, the trend is for lower temperatures and as hinted above, some evolutions go for a Scandinavian trough. The run up to Christmas is also looking quite interesting but we have plenty of weather action to get through before then. In the meantime, the relatively dry, cold and very stabil weather pattern is about to change and kick off is at the end of this coming week...
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