Heavy Snow and Heavy Rain in Alaska, May 25, 1999

Much of the Copper River Basin experienced an unusual late May precipitation event. A weakening surface/upper air low drifted north through the eastern Gulf of Alaska Monday. Very cold air aloft, associated with this feature, preceded the center into the upper Copper River Basin and even the upper Tanana Valley (WSFO Fairbanks area). As the original upper center died in the northeast Gulf of Alaska, a new center formed near the Alaska-Canadian border. Warm air at lower levels and increasingly colder air aloft caused rapid de-stabilization of the airmass across the southeast Alaska mainland and thunderstorms converged into a very wet, 150 mile wide band. Snow was also reported at elevations as low as about 1500 feet in the Copper River Basin...with Gulkana airport picking up over 3 inches and other, higher elevations recording nearly a foot of new snow. Liquid precipitation amounts at the Gulkana ASOS were very close to 1.5 inches for roughly a 19 hour period from just after midnight to just after 7pm Tuesday. Unofficial reports of 2.5 inches of rain were received near the Alaska Range boundary of the Anchorage and Fairbanks Forecast office area of responsibility.