Japan Sees Near World Record Snowfall Thanks To Several Feet Of Sea-Effect Snow

This Is Why Japan Is Seeing Incredible Snowfall

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Snow measured in feet is blanketing parts of Japan this week, with snowfall rates among the highest on record. This is due, in part, to a phenomenon called sea-effect snow.

W​hat happened: Beginning Monday, heavy snow hammered parts of Japan, particularly the northernmost main island, Hokkaido, and along and west of the spine of the Japanese Alps on the largest island, Honshu.

A​ccording to the Japan Meteorological Agency, seven different locations have picked up over 100 centimeters (39.4 inches) of snowfall this week. Shirakawa, on the western side of Honshu, reported 134 centimeters (52.76 inches) of snow had fallen since early Monday, according to the JMA.

T​he heavy snow closed runways, forced flight and school cancellations, blocked some roads, stranded vehicles and interrupted train service in Hokkaido, the Associated Press reported.

A​mong the heaviest snow measured: Aside from the impressive totals, it was how fast the snow fell that grabbed the attention of meteorologists.

M​onday, a reporting station at Obihiro, Hokkaido, measured 47.24 inches of snowfall in just 12 hours. That more than doubled the station's previous 12-hour snowfall record in 26 years of data, according to the JMA.

F​ive other locations in Hokkaido also set new 12-hour snowfall records since the mid-1980s.

W​eather historian Christopher Burt noted this was also among the heaviest 12-hour snowfalls on record anywhere on Earth.

In North America, Burt found only Thompson Pass, Alaska (48 inches in 11 hours on Dec. 16, 2017), and Montague Township, New York (40 inches in 12 hours Jan. 11-12, 1997) have seen a snowfall rate near the magnitude of what occurred in Obihiro, Japan.

Burt cautioned that Canada, Japan and the U.S. are the only countries that maintain regular, detailed snowfall statistics. The World Meteorological Organization doesn't maintain snowfall records in their archive of world and continental records.

F​irst, Monday's intense snowfall rate appeared to have been due to a low-pressure system that intensified in quickly in the northern Sea of Japan, forcing moist air strongly upward over lingering cold air over Hokkaido.

B​ut that also set up a classic pattern for what's called "sea-effect snow" that is continuing this week in some areas.

The mechanism is similar to what produces heavy lake-effect snow in the Great Lakes. In this case, bitter cold air from Siberia and Manchuria - where temperatures are well below zero - is dragged over the relatively warmer water of the Sea of Japan.

T​his unstable stacking of very cold air above warmer water forms bands of heavy snow that are then blown ashore in western Japan and lifted by the Japanese Alps. Just as in the Great Lakes, as long as this pattern continues, so will bands of heavy snow.

B​ut that pattern also means areas to the east and south of the Japanese Alps typically pick up much less snow. That's because the moisture from these winds are wrung out over the mountains, then move downslope and dry out. Tokyo, for example, averages only about 4 inches of snow a year.

S​ome of the heaviest snowfall on Earth: This proximity to Siberian cold air makes Japan's sea-effect snowbelts among the most prolific on Earth.

Sukayu, a resort location in far northern Honshu, averages an incredible 694.5 inches, or almost 58 feet, of snowfall each year, according to the JMA.

The highest known 24-hour snowfall and snow depth measured on Earth appears to have been at Japan's Mt. Ibuki, climate scientist Yusuke Uemura told weather historian Christopher Burt.

At an elevation of 5,000 feet, Mt. Ibuki picked up 90.6 inches (about 7.5 feet) of snow on Feb. 14, 1927, leaving 465.4 inches of snow on the ground.

T​his yearly pummeling requires some adaptations. As Burt wrote in "Extreme Weather", homes there have longer eaves called gangis that overhang sidewalks to help keep them less snow choked. Deep snow on roofs must be swept off into streets, where underground sprinklers can spray water to melt at least some of the snow.

Jonathan Erdman is a senior meteorologist at weather.com and has been covering national and international weather since 1996. Extreme and bizarre weather are his favorite topics. Reach out to him on Bluesky, X (formerly Twitter) and Facebook.​