Western Norway is bracing for the impact of an atmospheric river this week, leading to heavy rainfall and multiple weather warnings across the region. The Meteorological Institute (Meteorologisk institutt) has issued yellow warnings for landslides and floods, particularly targeting the Oppdal region, and red avalanche warnings for the Trollheimen mountains.
According to meteorologist Sigrid Auganæs, the severe weather is anticipated to begin with full force Monday night, extending through Tuesday and Wednesday, when the heaviest rains are expected. "This looks like someone is spraying with a garden hose at Westlandet," Auganæs stated, as she explained how the atmospheric river operates.
An atmospheric river consists of extensive amounts of water vapor suspended within the air, capable of transporting moisture across great distances. The phenomenon, which can stretch thousands of kilometers, is significant for moving humidity but can also result in severe rainfall when it stalls over land, something Western Norway will soon experience.
While the initial impact of the storm was expected to be less intense, Auganæs indicated, "The atmospheric river has already started, but the main impact will not be felt until Tuesday." The storm system—not typical low-pressure weather—will lead to hazardous conditions, with warnings of potential rainfall amounts reaching up to 120 millimeters within 24 hours.
Areas like Bergensare and other regions accustomed to such moisture will need to prepare for difficult driving conditions, as small creeks may overflow, potentially inundated roadways. "Bergeners have likely experienced this many times before, but this type of humidity arrives with an atmospheric river, differentiates itself from the usual low-pressure systems along the coast," Auganæs added.
With the mixture of rain and heavy winds, concerns have been raised about snow levels, which will flex throughout the storm due to rising temperatures as the warm air interacts with the cold mountains. Meteorologist Ingrid Opheim Bækkelund noted, "The snowfall level will vary, but as it looks now, more precipitation is expected inland compared to the coast."
The Norwegian Water Resources and Energy Directorate (NVE) has also issued red alerts concerning avalanche dangers, alongside warnings for floods and mudslides, creating serious risks across Western Norway. Snow depths over 50 centimeters will heighten the chances of slush avalanches and land movement.
Local residents and travelers are urged to heed warnings closely, especially those planning to engage with mountainous activities. Bækkelund emphasized the importance of preparation, stating, "Be cautious of warnings if you're moving around the mountains. This applies to traveling as well," highlighting the potential for severe conditions.
Projected temperatures over the next few days will hover around freezing, with high winds expected to intensify throughout the storm, contributing to challenging conditions. Rain is forecasted to significantly increase across the region's valleys, coupled with strong winds gusting up to 26 m/s.
Authorities warn of potential disasters within urban areas, as stormwater issues may also arise. The warnings specify concerns of high water levels, blocked roads, and difficult travel conditions due to possible flooding. Multiple warnings spanning from Rogaland to Møre og Romsdal have been issued, with the most intense effects expected at Hordaland and Sogn og Fjordane.
The overly moist conditions manifesting from the atmospheric river could lead to uncontrolled water flows during this week. It is this unpredictable but potentially high-impact weather system, which Auganæs metaphorically described as the atmospheric river "hose" moving slowly north and then south, as it calms down midweek.
Forecasters expect the situation to ease later this week, with diminished rainfall expected from Thursday onward. The public will still need to remain vigilant as some rain may persist, albeit less heavily. Overall, the atmospheric river presents significant threats and challenges for Western Norway, emphasizing the urgency of preparedness and caution as conditions develop.