Extreme storm could bring dangerous amounts of rain to central Europe
An unusually cold and intense storm is pounding central Europe with tremendous amounts of rain and early season mountain snow. The storm, named Boris in parts of the continent, could bring once-in-a-generation flooding in locations that end up hardest hit by torrential rain, while feet of snow are expected pile up in the Alps.
The U.K. Met Office warned of “extreme rainfall” for central and southern Europe. “Some rivers may experience 1 in 100 year events,” it tweeted.
French and Swiss disaster officials are warning of catastrophic flood risk for parts of central Europe.
“The current forecast maps are reminiscent of the catastrophic floods of 2002, when a similar weather pattern led to devastating floods in the Czech Republic, Austria and eastern Germany,” wrote MétéoSuisse, the government meteorological agency in Switzerland, on Thursday.
Already, snow has accumulated for the first time on record during September in parts of the Austrian Alps, while heavy rain has triggered flooding at lower elevations in Austria and Slovenia.
Heavy precipitation falling over central Europe on Friday is poised to shift toward Eastern Europe this weekend before slowly losing intensity and perhaps backing west toward the Mediterranean Sea to start next week.
From the Adriatic Sea northward toward Austria and Poland, the first rounds of heavy precipitation have already swept through, with some flood alerts issued.
Slovenia has been particularly hard hit so far with numerous reports of 5 to 6 inches of rain and flooding. Austrian officials are urging people to avoid travel, including in the capital of Vienna.
Italy and parts of Greece were also hit by severe flooding about a week ago; saturated soils will make these areas prone to additional flooding with the incoming storm.
The intensity of the precipitation is forecast to ramp up into Saturday.
“This is a completely exceptional event in climatological terms, and we can already fear serious flooding with heavy consequences, taking into account the population density of the regions concerned,” tweeted forecasting engineer Gaétan Heymes.
Cold air wrapping into the storm brought the first widespread frost of the season to parts of the United Kingdom. The Met Office reported temperatures as low as 27 degrees Fahrenheit in Topcliffe, England. High-elevation locations in mainland Europe have seen considerably colder conditions, the coldest so early in the season in decades in some spots.
That cold air is already helping snow pile up at high elevations to more than a foot in the Austrian Alps. Several locations there have reported their first September snowfall on record.
“This is about as cold as it gets this early in September,” tweeted Scott Duncan, a meteorologist in the United Kingdom.
What’s behind the big storm?
The storm formed as a lobe of Arctic air swept southward through western and central Europe and then clashed with warm, moist air to the east and south.
The storm has since become cut off from the steering currents of the jet stream, which means it will linger over Europe for days. As it does so, it will keep drawing moisture-filled air from the historically warm Mediterranean Sea into the region.
Weekend forecast
Up to a foot of additional rain is forecast in Austria and the Czech Republic, more than twice the amount most places in these countries typically receive during September. Totals of 3 to 5 inches will probably be common from Switzerland and eastern Germany to the western portion of Ukraine, and then south toward the Mediterranean, including Italy.
In the Czech Republic, water is being released from some reservoirs in anticipation of the heavy rainfall.
Rainfall rates could become extreme at times through Sunday to the north and northwest of the storm center, where the cold front associated with the storm will focus moisture streaming northward.
Early taste of winter
Heavy mountain snow has already begun falling in the Swiss and Austrian Alps. The Austrian Alps are poised to receive the most snow. Some high-elevation locations may see up to 12 inches in as little as six hours over the weekend, following bouts of heavy snow since Thursday. Storm totals could surpass five feet in some of the highest elevations.
Heavy snow is also falling in the Swiss Alps. Through midday Friday, at least 4 inches had fallen in Murren in the country’s central mountain region, according to Tom Niziol, who was the Weather Channel’s winter weather expert before retiring and is vacationing there.
As much as 20 inches has already been reported so far in parts of the Austrian Alps.