The first half of the calendar winter was very mild. In Moscow, the average temperature of the period (December 1 - January 15) was +0.6. It is not very warm in winter (the plus sign is an indicator), but it is significantly lower than in the 2006-2007 season. Then the average temperature in the first half of winter was historical (+1.5)!
The atmospheric situation is characterized by the predominance of the positive phase of the North Atlantic Oscillation (a large pressure gradient between Iceland and the Azores), which leads to strong westerly-southwesterly winds that carry the Atlantic heat to Europe and western Russia.
Surface temperature and wind direction in the middle troposphere January 15, 2020
Since winters in Russia are usually quite harsh, the temperature significantly exceeds the norm and reaches record values on some days. In particular, in St. Petersburg on January 15, a new all-day high was set (+7.6).
It is important to note that the active Western transfer "girdles" all of Russia. As a result, the zone of thaw weather reaches the Urals, and in Siberia (instead of the usual Siberian ones) frosts are European-style "orphan". The double-digit minus region covers only Eastern Siberia and Yakutia.
The positive temperature does not allow the establishment of snow cover in the North-West and in Central Russia. For example, in Moscow on January 15, its height was 3 cm. Over the past 20 years, it was less only once - in 2007. In turn, snowlessness has a positive feedback with abnormally warm weather, since it does not reflect (as usual), but absorbs most of the solar radiation.
Snow depth in Moscow on January 15 from 2000 to 2020.