Jonathan Erdman
Juneau, Alaska's record-setting 24-hour rainfall, compared to the previous 24-hour record and the average precipitation for the entire month of December.Juneau, Alaska, smashed its all-time 24-hour rainfall record Tuesday and Wednesday, triggering destructive flooding and mudslides from an atmospheric river.
Juneau picked up 5.08 inches of rain in 24 hours ending 3 a.m. Wednesday, topping the previous record for any 24-hour period in Alaska's capital city, 4.66 inches on Oct. 9-10, 1946, according to Rick Thoman, a climate specialist at the University of Alaska-Fairbanks.
Two other towns, Pelican (9.75 inches) and Skagway (5.37 inches), also set new all-time calendar-day rainfall records, according to Alaska-based climatologist Brian Brettschneider.
This torrential rain triggered flooding and mudslides in parts of the city, particularly in the neighborhoods northwest of downtown near the Mendenhall Valley and Juneau International Airport.
One mudslide damaged a home in the Salmon Creek neighborhood. Another mudslide less than a mile away threatened a city park, KTOO-TV reported.
Jordan Creek in the Mendenhall Valley was pushed to its highest level in at least eight years Tuesday – above the level the National Weather Service said would result in flooding of homes and businesses in the Jordan Square area. As a result, roads and parking lots were flooded.
Local officials warned of high avalanche danger due to the heavy rain, particularly along Thane Road southeast of downtown, where the season's first avalanche occurred Tuesday.
Multiple landslides isolated the town of Hyder, about 230 miles southeast of Juneau, from its closest town, Stewart, British Columbia. Power has been out for two days, according to the NWS in Juneau.
A mudslide closed the only road out of Haines, about 75 miles north-northwest of Juneau, on Wednesday, cutting off access to the town's airport and ferry terminal. Haines also shattered its all-time one-day and two-day rainfall records, according to the National Weather Service.
A Record Soaking, Even For Southeast Alaska
Southeast Alaska is one of the wettest locations in the U.S.
In an average year, measurable precipitation falls three out of every five days in Juneau. The town of Yakutat, Alaska, averages a whopping 155 inches of precipitation per year, over three times that of Houston.
So what made this event a record-breaker?
The Pacific jet stream, which typically guides storms from west to east across the Pacific Ocean this time of year, ran into a roadblock in the form of a ridge of high pressure over the U.S. West Coast.
That forced the jet stream to buckle northward, tapping a plume of deep moisture known as an atmospheric river and channeling it into southeastern Alaska.
The setup for the Dec. 1-2 heavy rain event was an atmospheric river pumped northward into southeastern Alaska.But it wasn't simply the atmospheric river.
"This type of setup with these atmospheric rivers impact the panhandle quite often," NWS meteorologist Caleb Cravens told KRBD Radio. "But what makes this one stand out is the rainfall rates that we are getting."
This deluge followed the fifth-wettest November on record in Ketchikan, Alaska, one of southeastern Alaska's wettest towns and home to the famous liquid sunshine (rain) gauge.
In 2019, southeastern Alaska was one of the few areas of the U.S. in severe to extreme drought, a drought that didn't end until mid-January 2020.
The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.
The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.
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