A Look Across the State
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A Look Across the State
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| December 2006 Summary | |||||||||||||||
| The Arctic Oscillation, an index of circulation in the Arctic, was definitively positive throughout the month of December, particularly during the second week. Circulation aloft over Alaska was weak during the opening week as a north Bering Sea low moved ashore over northwest Alaska and weakened. In the third week, south winds aloft developed over the eastern mainland, and vigorous onshore flow swept over Southeast Alaska for the remainder of the month. Westerlies were prevalent over the Aleutians until the month's closing days. | |||||||||||||||
| Across the Arctic, brisk southwest winds blew over the area on the first two days of the month helping to raise temperatures for coastal communities that averaged up to 8°F above normal for the month. Easterly flow prevailed from the 3rd through the 20th followed by a period of uncommonly light winds, at times cold and offshore, from the 21st through the 31st. Coastal areas from Barrow westward had far above normal snowfall; in contrast to eastern sections of the coast from Prudhoe Bay eastward, which received less than half the normal amounts. The West Coast had southerly gales on the 1st and 2nd ; followed by predominantly cool northeast flow for most of remaining December. This resulted in both below normal temperatures and far below normal precipitation from the Seward Peninsula southward. Areas to the north surrounding Kotzebue Sound, however, enjoyed milder temperatures from 4° to 8°F above normal. The entire Aleutian Island chain remained cooler than normal and also very dry. Across the Interior, temperatures switched from November's persistent cold to above normal at most locations during December. Only a very small portion of lowland areas between Fairbanks and Fort Yukon had slightly below normal temperatures. Abnormally mild temperatures averaging more than 10°F above normal extended from the central Brooks Range southeastward into the Yukon Flats. Temperatures at Eagle soared to a new December record of 51°F on the morning of the 20th - just a day before winter solstice. Temperature inversions were common during December with overall monthly temperatures in the hills 5° to 10°F above those down in the valleys. Light snowfall continued nearly all month, providing little hope for serious winter sports, but a crucial accumulation around Christmas allowed some area alpine ski slopes to open at last, just in time for the season. Abnormally unstable air aloft from the Gulf of Alaska flowed into the Yukon at month's end - with a freakish result. At Eagle, just west of the Alaska/Yukon border, John Borg, the National Weather Service river and weather observer for many years, reported a remarkable morning thunderstorm on the 30th, a winter weather event probably not seen there in the 108 years since Eagle was settled. Between this and the warmth on the 20th, residents may have been wondering if it was late April. The Southern Mainland had periodic northeast gales around a continuing onslaught of Gulf of Alaska storms for all the month. One of these storms brought winds well over 60 mph to Yakutat on the evening of the 19th; where the wind blew off the roof of the National Weather Service office. The longstanding snow drought of the winter through mid December was decisively broken on the 20th and 21st as nearly 3 feet of snow fell in Valdez. The weight of this heavy snowfall sunk the fishing vessel “Double Trouble” in Valdez harbor. Over a foot of snow fell in Anchorage from the 18th through the 21st, and there were considerably heavier amounts up in the foothills of the nearby Chugach Mountains. This sudden and heavy accumulation of snow contributed substantially to nearly 100 auto accidents around Anchorage. Portions of the typically snowier western portion of Susitna Valley received just half of normal amounts, whereas the adjacent climatically drier populated eastern valley areas had up to twice normal December snowfall totals. Two avalanches occurred on the Richardson Highway north of Valdez, closing a 30 mile stretch of the road for a day. Extensive plowing, and blasting to bring down snow on avalanche prone slopes, finally opened the road. This same stretch of highway had been flooded just two months earlier during the second week in October after torrential rains. Southeast Alaska shared stormy Gulf of Alaska weather with the southern mainland nearly all month. Consistent southerly winds brought temperatures up from their frigid levels of November. All areas had above normal temperatures, except for Skagway, catching a colder outflow from Canada's adjacent Yukon Territory. Precipitation everywhere was well above normal - up to twice the already wet late autumn totals normally received here. On the night of December 18th - 19th, the Alaska lightning detection network picked up a total of 44 lightning strikes during a mid winter outbreak of coastal thunderstorms. Such events typically occur once every year or two. Down in Ketchikan, a windstorm on the 21st brought down some large trees; one fell onto a house causing considerable damage, but fortunately no injury. Marine Weather was constantly unsettled during December. Gale force winds blew somewhere in Alaskan waters during every day of the month. The storm of the month swept into the central Gulf of Alaska on the 19th as a 944 mb (27.88”) low. This weather system brought widespread storm force winds and heavy seas to the entire coast from the southern Kenai Peninsula down to Ketchikan. In addition, the storm brought extensive heavy snowfall to the southern mainland as far west as Anchorage, and to the Southeast Alaska mountains. The sea took a toll during the month, though this toll was clearly limited due to the small number of ships that ventured from port to face December's storms and darkness. On the 23rd, 3 people aboard a 14 foot runabout were caught in blizzard conditions and rough seas on their way out of Whittier. They were able to make it to shore at some distance from the harbor, and were eventually rescued. Their boat sank in heavy seas while a harbor tug attempted to tow it back to port. |
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Statewide Extremes
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Statewide Temperature and Precipitation
Departure Maps |
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| River conditions subtly revived from the mid winter cold at some locations. Warm weather during the first 10 days of the month brought considerable overflow up on the ice of the Chena River near Fairbanks; the overflow weakened the ice. On the 2nd, a pickup truck broke through the ice on the ice bridge on the Chena River near Pike's Landing. Early in the month, the river ice in this area had been measured near 20 inches thick. Cooler weather in the second half of the month lessened such problems. Southeast of Fairbanks, overflow along Badger Slough caused water to flow into some basements of nearby houses. Down in the southern mainland, heavy ice cover on the Kenai River in Soldotna broke lose in some locations, and formed ice jams as the river carried it downstream. Rising river levels resulted upstream from the ice jams, and there was considerable river ice damage to metal walkways that are normally about 8 feet above the water level. Sea surface temperatures in the Gulf of Alaska were about 2°F colder than normal. In the Bering Sea, surface waters cooled down to near normal levels during December. Waters in the central Chukchi Sea were at well above normal levels for the first 10 days of the month, prior to a rapid freeze over during the next several days. Sea Ice coverage in the central Chukchi Sea remained at record low levels, as much of the area was ice free for the first 10 days of the month. This area then rapidly closed in. Shore fast ice along the Bering Sea coast of Alaska extended clear down to Pilot Point on the north side of the Alaska Peninsula, on the first of the month. This ice steadily grew, covering Norton Sound by the 6th, and reaching Saint Lawrence Island on the 11th. Bering Strait was closed by ice on the 13th. Through mid December, ice cover in the Bering Sea was well above normal in Bristol Bay, and near record low extent toward Bering Strait. By the end of the month, the Bering Sea ice pack extended down as far as Cape Seniavin on the Alaska Peninsula, up to 40 miles west of Nunivak Island, and was closing in on Saint Matthew Island in the middle of the Bering Sea. Ice coverage at month's end ranged from well above normal in southern Bristol Bay to near normal in the north Bering Sea - thus reflecting the rapid growth of ice there. In Cook Inlet, ice cover extended just past the Forelands on the first, and then grew south around Kalgin Island and over the west shore down to Cape Douglas by mid month. The ice receded slightly during the second half of the month as temperatures rose. Summary information is compiled and produced monthly by the Fairbanks Forecast Office of the National Weather Service and the Alaska Climate Research Center, with contributions by Ted Fathauer, Anton Prechtel, and Martha Shulski. Portions of this summary appear in Weatherwise magazine. Preliminary climatological data are used for the graphical products. For official data, please contact the National Climatic Data Center. Posted: January 11, 2007 |
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