Arctic outbreak evolution and snowfall forecast, Jan 5-7, 2017
This is a follow-up on the evolution of a significant arctic outbreak through the next few days as a very cold airmass is advecting into east-central Europe and Balkan peninsula. Once the cold upper levels slip into Mediterranean, a secondary cyclogenesis will take place over Italy and move towards Greece – it should result in excessive snowfall events, extremely cold temperatures and combined with strong winds, windchill temperatures will be locally below -25°C. The airmass over the broad area will be very cold, especially across the white-shaded areas where a few days period of arctic cold airmass with temperatures near 20 °C below average for this time is expected!
Here is the late afternoon analysis of arctic airmass spreading across Europe – very cold in Scandinavia and Baltic States, it continues across CNTRL-E Europe towards the Balkan peninsula and the Mediterranean:
In response to the deep cyclone trailing along the southern edge of the trough and sea-effect snow, an excessive snowfall is expected over broad areas:
Northern Alps: Locally 30-75 cm of fresh snow across northern half of the Alps. Local accumulations may exceed 75 cm. Some fresh snow also over S Germany, Switzerland, the rest of Austria and Czech Republic.
WSW Balkan peninsula: locally 30-60 cm of snowfall at higher elevations as well as across N Bulgaria, E-SE Romania, Moldova and S Ukraine.
E-SE Italy: very significant Adriatic sea-effect snow as strong northeasterly Bura/Bora winds blow across the Adriatic. Expect locally up to 75 cm of sea-effect snow.
Central Greece, Attica and E parts of Thessaly:
Below is the extreme cold and excessive snowfall outlook through the next 3 days:
Due to very sharp temperature and pressure gradient between Balkan peninsula and Adriatic sea, extremely severe Bora winds are likely along the E Adriatic coasts below Velebit mountains in Croatia, especially over Kvarner and Dalmatia regions. Gusts could locally exceed 150 km/h!
The very cold air at mid and upper levels produced some impressive convection and thunderstorms over the Adriatic sea, especially for January.
Strong snowfall and strong winds are already being reported:
Here is an overview of the pattern itself, revealing a strong upper ridge over western Europe and a deep cold with arctic airmass pushed onto the Balkan peninsula and Mediterranean tonight. Near -20 °C over W Balkan at around 1500 m ASL, significant temperature anomaly and very low windchill temperature:
Follow snowfall with the following radars: