Atmospheric River brings Historic Flooding to Juneau, AK (Photo Credit: Aaron Jacobs/National Weather Service)
A man stands outside his property near Jordan Creek on October 27, 2017
During the week of October 23rd, hints of a strong atmospheric river (a narrow band of concentrated moisture in the atmosphere) were present in the extended forecast for southeast Alaska, as moisture from super typhoon Lan was expected to push through. Typhoon Lan formed in the northwest Pacific on October 14th, affecting the Philippines, Japan, and South Korea and causing several deaths along its track. By October 23rd, Lan was showing signs of dissipation. The remnant moisture fueled the atmospheric river, bringing heavy flooding to Alaska.
On Wednesday, October 25th, an areal flood watch had been issued for the northern half of southeast Alaska due to projected small stream rises. As rain began on Thursday, a flood advisory was in effect, where rivers reached bankfull and high freezing levels (>6000 ft) increased the threat for runoff and higher elevation snowmelt. Early Friday morning, heavy rains and strong winds near 40 mph continued to impact the Skagway and downtown Juneau areas. The 48-hour rainfall totals for Thursday and Friday ranged from 3.78” at Yakutat Airport, 4” at the Glacier Bay Fuel Dock in Gustavus and at the National Weather Service office in Juneau, 4.5” for downtown Juneau, 6” at Sawmill Creek in Sitka, and 8” in Pelican.
By 10 a.m. on Friday, October 27th, a flood warning was issued for Juneau Creek near Juneau. Jordan Creek usually reaches action stage at 9.2 ft, flood stage at 9.7 ft, and moderate flood stage at 10.5 ft. It reached a record crest of 11.0 ft by 2:30 p.m. local time on Friday. The last historic crest of Jordan Creek occurred on September 9, 2016 at 10.18 ft. As a result, several residential homes, office buildings, and roads near Jordan Creek (and also Salmon Creek in Gustavus) were inundated by a foot of water. A mudslide occurred near the Mt. Roberts Tramway system in Juneau, closing roads and delaying traffic.
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© 2017 Meteorologist Sharon Sullivan