A Siberian cold snap is coming to Bosnia and Herzegovina

Prepared by: Nedim Sladić, amateur meteorologist

A strong influence of cold air mass will be felt from the weekend, when temperatures will drop significantly next week, reaching as low as -20 degrees Celsius in the lowlands of Bosnia in the mornings towards the end of February. The temperature anomaly according to the ECMWF prognostic model has initialized at as much as 12 to 20 degrees below the long-term average, which is an extremely strong extreme considering the deviation. From Sunday and throughout most of next week, temperatures will be below freezing all day, not only in Bosnia, but in some parts of Herzegovina as well. The consequence of this will be a so-called blocking situation, where the anticyclone field over Scandinavia unhindered pushes the cold air mass to descend via the northeastern high-altitude current towards most of the European continent.

Over the Mediterranean, this situation is sufficient to intensify and develop stronger cyclonic systems that would spread towards the Adriatic and cause heavy precipitation, and this will be the case this time in Bosnia and Herzegovina as well, starting this weekend in our country until Wednesday. Due to the proximity of the southern Adriatic cyclone, heavy precipitation is expected on Monday and Tuesday. The forecast is based on deterministic prognostic material: ICON-DWD 0.065°, GFS 1.0°, runs 18Z (21.02), 00Z, (22.02), ECMWF-CEP, ECMWF-EPS (HRES) 0.25° and 1.4°, runs 00 and 12Z, comparison made with the UKMO model. The ensemble is based on the GFS 0.25° model and 800 perturbations, starting from February 17th.

Thursday, February 22, 2018: a cyclonic vortex in the Tyrrhenian Sea and its proximity to our regions cause unstable weather in Bosnia and Herzegovina. It will be mostly cloudy with snow in most of Bosnia and in some higher areas of northern Herzegovina, and light and patchy rain and sleet in the far east and northeast of the country. Heavy precipitation in low-lying Herzegovina and southwestern Bosnia, and due to the distance from the cyclonic influence, there is the least in the far northeast of the country. The predicted amount of precipitation is from 10 to 25 liters per square meter in most of the country, except for northeastern Bosnia where the amount of precipitation is less than 3 liters per square meter.

In low-lying Herzegovina and western Bosnia, the expected amount of precipitation ranges from 25 to 40 liters per square meter. Up to 15 cm of new snow will fall in most of Bosnia. The wind will be moderate to moderately strong, northeastern in the far north of Bosnia, and light to moderate in the rest of the country, from the east. Morning temperatures will be from -2 to 2 degrees Celsius, up to 6 degrees in southern Herzegovina. The highest daily temperatures in Bosnia will generally be similar to the morning values, except in Herzegovina where daily temperatures will range from 6 to 10 degrees Celsius.

Friday, February 23, 2018: the Tyrrhenian cyclone continues to affect unstable weather conditions in Bosnia and Herzegovina, but its influence will gradually weaken by the end of Friday. It will be mostly cloudy with snow in northern and northwestern Bosnia, and rain in low-lying Herzegovina and parts of northern Herzegovina, central, eastern, and northeastern Bosnia. Heavy precipitation in low-lying Herzegovina and southwestern Bosnia, where the predicted amount of precipitation ranges from 15 to 25 liters per square meter. In the rest of Bosnia, it will be mostly between 1 and 7 liters per square meter. The predicted height of new snowfall is up to 4 cm. The wind will be light, from the northeast, and a strong bora will be observed in Herzegovina. Morning temperatures will be from -3 to 0 degrees Celsius, from 1 to 5 in the south. The highest daily temperatures will be from -1 in Krajina to 6 in the northeast of the country, and from 6 to 10 degrees Celsius in southern Herzegovina.

Saturday, February 24, 2018: a pronounced pressure gradient between a strong anticyclonic field over northeastern Europe, which extends its ridge of influence towards our regions, and a cyclonic field over southern Europe causes windy weather with a bora in Herzegovina and temporary weakening of precipitation in most of Bosnia and Herzegovina. The anticyclone over northeastern Europe also marks the beginning of the strongest cold wave in Bosnia and Herzegovina, as a large amount of extremely cold air mass will unhindered flow from the territory of Russia. It will be mostly cloudy with light snow. The wind will be moderate, from the northeast and east, and a moderate to strong bora in Herzegovina. Morning temperatures will be from -3 to 0 degrees Celsius, from 0 to 3 degrees in the south. The highest daily temperatures will be from 0 to 3 degrees Celsius, and from 3 to 8 degrees in southern Herzegovina.

Sunday, February 25, 2018: the renewed approach of a new cyclone from the Mediterranean and its entry through the Tyrrhenian Sea into the southern Adriatic destabilizes the atmosphere over Bosnia and Herzegovina. It will be mostly cloudy and unstable, accompanied by snow. From midday, precipitation will intensify. Due to low temperatures, snow is expected throughout the country, including both parts of Herzegovina (northern, i.e., high-lying and low-lying). The wind will be moderate to strong, from the northeast and east, and a moderate to strong bora in Herzegovina. Morning temperatures will be from -10 to -4 degrees Celsius, from -3 to 3 degrees in the south. The highest daily temperatures will be from -6 to -2 degrees Celsius, and from -2 to 2 degrees in southern Herzegovina.

Monday, February 26, 2018: a shallow cyclone over the coasts of Albania and the southern Adriatic causes precipitation, and due to the influx of extremely cold air mass, temperatures in Bosnia and Herzegovina are extremely low for this time of year, with a very pronounced negative anomaly, sometimes up to -15 degrees from the long-term average. It will be mostly cloudy with snow, and intermittent heavy snowfall is predicted for southeastern, central, and northwestern Bosnia. The predicted height of new snowfall ranges from 5 cm in Herzegovina, and from 15 to 30 cm in most of Bosnia, with locally up to 50 cm in central and northwestern regions. In the mountainous areas of Bosnia, with heavy snow accompanied by strong winds (blizzards), over 1 meter of new snow is expected. The wind will be moderate to strong, from the northeast and east. Morning temperatures will be from -14 to -5 degrees Celsius, and from -5 to -2 in the south. The highest daily temperatures will be from -10 to -6 degrees Celsius, and from -5 to -2 in the south.

Tuesday, February 27, 2018: a shallow cyclonic field in the southern Adriatic supports unstable weather in our country. It will be mostly cloudy with snow, heavier and more abundant in southeastern, central, and northwestern Bosnia. In Herzegovina, the snow will be of lesser intensity. The predicted height of new snowfall is 1 to 3 cm in Herzegovina, and between 10 and 20 cm in most of Bosnia, except for southeastern, central, and northwestern Bosnia where an additional 20 to 30 cm is predicted. The wind will be moderate, from the northeast, weakening during the day. Morning temperatures will be from -16 to -8 degrees Celsius, from -8 to -5 in northern Herzegovina, and from -5 to -2 in low-lying Herzegovina. The highest daily temperatures will be from -11 to -5 degrees Celsius, and from -5 to -1 in Herzegovina.

Wednesday, February 28, 2018: it will be mostly cloudy and very cold with intermittent, weakening snow. In the afternoon, precipitation is expected to stop throughout the country, with partial clearing. Morning temperatures will be from -21 to -12 degrees Celsius, from -14 to -8 in northern Herzegovina, and from -8 to -4 in low-lying Herzegovina. The highest daily temperatures will be from -15 to -8 degrees Celsius, and from -7 to -2 in Herzegovina.

Thursday, March 1, 2018: extremely low morning temperatures, with temperatures even -18 degrees below average, are associated with the cold air mass from northeastern Europe. It will be slightly to moderately cloudy and sunnier, but extremely cold. Morning temperatures will be from -26 to -22 degrees Celsius on plateaus, highlands, and mountains of central and northwestern Bosnia, from -22 to -14 in the lowlands, and from -13 to -5 degrees Celsius in Herzegovina. The highest daily temperatures will be from -14 to -7 degrees Celsius, and from -7 to -3 in the south of the country.

After a relatively mild winter, winter will not pass without a strong cold snap after all.