Flood — Taiya Inlet, Alaska

2018-08-08 to 2018-08-10 · near Skagway, Taiya Inlet, Alaska

Event narrative

After a very dry period for the northern inner channels of Southeast Alaska moderate to heavy rains moved over the area on August 7th. The high rain rates continued for the next forty-eight to seventy-two hours. Rainfall totals from this time frame ranged from two to three inches near sea level with four to five inches in the headwaters at higher elevations. The very warm temperatures created very high freezing levels that increase runoff from snow or ice melt. The Taiya River started to rise through the early morning hours of August 7th and went above minor flood stage of sixteen point five feet by the late afternoon. The river continued to rise at a stair step fashion through the night and into the morning hours of August 8th. By the early afternoon the water levels rose above moderate flood stage of seventeen feet and then leveled off some as the rain rate relax some through the early evening hours of August 8th. There was a big push of moisture that moved over the area in the early morning hours of August 9th and the river began to rise very steeply. The Taiya River crested in the late morning on August 9th at eighteen point twenty-one feet almost a foot and half over the moderate flood stage of seventeen feet. The rain slowly diminished through the overnight hours of August 10th and the river slowly receded to be below minor flood stage by the morning hours of August 10th. The National Park Service reported that there was significant flooding along the Chilkoot trail with waist deep water along the lower portions of the trail. The international trail was closed for a few days due to the flooding and potential dangers.

Wider weather episode

A deep trough of low pressure with a long fetch from the North Pacific to the Gulf of Alaska produced a very strong and wet weather system. The atmospheric river slammed into northern southeast Alaska panhandle from August 7th and persisted through the 10th. The area received moderate to heavy rainfall with stations reporting two to four inches of precipitation at sea level with five inches at higher elevations. Along with the heavy rainfall there was very high freezing levels which ranged from eight to ten thousand feet. These high freezing level accompanied with the heavy rain increased the runoff from any snow left in the mountains and ice melt from area glaciers. All of the rain and snow/ice melt produce moderate flooding along the Taiya River and flooded the Chilkoot trail, part of the Klondike Gold Rush National Historical Park, near Dyea Alaska. The river crested around seventeen point thirty five feet which is above moderate flood stage of seventeen feet in the evening hours on July 23rd. The Mendenhall Lake also rose above moderate flood stage of ten feet and produced moderate flooding along the Mendenhall Lake area. The Mendenhall Lake gauge crested at ten point forty-two feet in the afternoon of August 10th.

View location on OpenStreetMap → (59.5116, -135.3431)

Source: NOAA Storm Events Database, event_id 774319. Narrative written by the NWS forecast office that issued the report.