Moderate to intense snowfalls will locally result in 20-40cm/36hrs
Very impressive setup is shaping up across Europe and the most important, also over central Europe and southern Alpine region. Very cold and snowy winter 2009/2010 continues perfectly.
Intense and deep polar trough with a strong cold front is blasting southwards across central Europe towards the Balkans. Moderate to heavy snowfalls are expected during the next 36 hrs. As can be seen from today’s maps, there will be two snowfall episodes this time. First, pre-frontal SW-erly flow and orographic precipitation mostly over western and SW-ern Slovenia overnight to Saturday.
Then secondary suface low (minimum central pressure slightly below 990hPa) in the morning hours with dry intrusion and kind of gap in precipitation across Slovenia for several hours. At the end, a strong cold front blasts in during the afternoon hours when precipitation will be mostly alined to this boundary. Heavy to intense snowfalls are then very likely along the rapidly moving front and especially over southern half of Slovenia in late afternoon/evening hours where front will be slowed down due to SE-wards moving secondary low from N Adriatic sea towards the central Balkans.
It looks like first episode will bring snow also to the lowlands across whole NE Italy and also down to near 200m ASL or slightly lower, while mixing is indeed possible as well as the coastal areas due to very cold airmass persisting over the region and quite a low dewpoints (near -3 to -6°C most of the locations). As the trough digs in, secondary cyclogenesis will take place over nothern Italy towards the morning hours and WAA will be pushed NE-wards into southern Slovenia. Models do agree that at the lowest levels up to 925hPa will rise above zero, where southerly winds will reach the ground (southern Brkini, Ilirska Bistrica valley and other areas near the SLO/CRO border). Towards the morning, southerly winds and stronger WAA will likely be pushed more northwards and affect most of southern/eastern Slovenia. Higher levels above 925hPa will stay with temps below zero. According to all this, snowfalls are still expected as long as precipitation are intense enough, while towards the morning when stronger orographic lifting will diminish, mixing rain+snow is possible for a couple of hours. Locally, freezing rain/sleet can occur if valleys will stay under inversion layer and winds will not succeed with mixing layers.
In the afternoon hours, strong cold front rapidly moves across Slovenia towards SSW and precipitation will increase along it. This front is clearly and most prefectly seen on the Murska sobota (NE Slovenia) HRID map:
As strong CAA arrives behind the front in the lowest levels, intense precipitation/snowfalls are quite likely due to greater forcing. As already mentioned above, the most intense will likely be over southern Slovenia where southerly flow aloft will combine with CAA beneath it and strong forcing will result. Given the rapid cooling and temps well below -6°C at 850hPa level, snowfalls will occur across whole Slovenia, including coastal areas towards the evening hours. Behind the front, moderately strong ENE-erly winds will arrive, as well as strong Bora in the SW Slovenia. There, deep snow drifts, blowing snow and extreme blizzard conditions will occur. Expect near zero visibility at times! Bora gusts will likely reach well above 150km/h again at the most exposed places in Vipavska valley, as well as other places known by extreme gusts in such situations.
As for the snow accumulations, it seems that 5-15cm are possible during the first episode by Saturday morning, especially over western and SW-ern Slovenia, while the second period from Saturday’s afternoon until Sunday morning could bring 10-20cm fresh snow all over Slovenia, with peaks exceeding 30cm locally over southern Slovenia. Total fresh snow accumulations by sunday morning could be as high as 30-40cm or locally even higher in Notranjska region, all depends how intense will be and how long precipitation will persist tomorrow during the second episode.
Precipitation will slowly diminish by Sunday morning, while the following days will be pretty cold again with temps below zero through all day. Stay tuned for future updates!
