Flash Flooding in Alaska, June 7 to 8, 1998

An unusually strong low pressure system moving north out of the central Pacific ocean brought high freezing levels and moderate amounts of rainfall to much of south central Alaska. With above normal snow pack at higher elevations the stage was set to raise water levels on south central Alaska rivers and streams to bank full conditions and in some instances with minor flooding. The affected areas included the Susitna, Kenai, and Resurrection river basins, as well as smaller streams in the Anchorage bowl area. An important precursor to this event was above normal snow pack conditions in the higher elevations of south central Alaska. The mountains along the Gulf of Alaska coast had received near normal snowfall through April, but a cool and very wet month of May, brought more snow to the mountains than any other month this past winter. Since April, freezing levels across the region had only topped 5000 ft a few times and for very brief periods. This allowed the higher elevation snow pack to ripen during May without contributing very much melt to the streams and rivers. In fact, some of the local meteorburst sites showed a loss of close to 3 inches of water equivalent from the snow pack in a 3 day period. A developing low pressure system on Friday, June 5th, in the central Pacific, near 35 north/175 west intensified rapidly and moved to near Cold Bay as a 975 millibar low by 4 p.m. Sunday afternoon. A long fetch of warm, moist air from subtropical regions was established to the east of the storm, due to a strong ridge of high pressure extending from the eastern Gulf of Alaska southward to the eastern Pacific Ocean. By Sunday morning, freezing levels across southern Alaska were in the 9-11 thousand foot range, allowing snow melt to take place across the entire Chugach and coastal mountain ranges. Anchorage bowl flooding was limited to some over bank flow along portions of Ship and Campbell Creeks. Minor flooding was taking place at the #Local Burgerman# restaurant, just D.S. of Old Seward Highway bridge over Campbell Creek, where overflow from the creek was entering the edge of the patio area for outside dining. On Monday, June 8th, the threat of flooding was further south over portions of the Kenai Peninsula. Indian Creek, just south of Anchorage, was flooding the wooded area surrounding the creek near the Seward Highway. Granite Creek was flooding low lying areas, but the campground parking sites were just above the water level. The East Fork of Sixmile Creek was causing some minor flooding of the woods and an access road just upstream of the Seward highway around 7 a.m....cresting later Monday afternoon. No flooding was apparent in the Seward basin, which includes Grouse Creek and Glacier Creek.