Federal meteorologists foresee a continuing cold winter for Alaska, followed by an unpredictable spring. But don't despair, they say. When June arrives, temperatures here should turn warmer than normal.

At least that's the most recent long-range forecast by the National Oceanic and Atmospheric Administration's Climate Prediction Center in Camp Springs, Md., which correctly called Alaska's recent cold snap.

Colder-than-normal surface sea temperatures off the south coast of Alaska -- which forecasters blame for diverting the polar jet stream farther north and making Alaska bitterly cold over the past three weeks -- should modulate by summer if the South Pacific warms first, they say.

Then the warmer-than-normal air temperatures that have prevailed over Alaska for most of the past decade -- "the 10-year trend" -- would have a chance to return, says Climate Prediction Center deputy director Mike Halpert.

"It's kind of like the old persistence thing," he said. "If it's been warm, it just often times continues to be warm."

Most recently, of course, Alaska has been anything but warm. The recent cold snap in Anchorage brought 11 straight days of double-digit negative temperatures to town -- while 2008 as a whole in Anchorage ranked as the coldest year in a decade.

"My retort to that would be: Well, one year doesn't make a trend," Halpert said.

But it did make for a fairly chilly summer. From May through August last year, Anchorage recorded its lowest average daily temperature -- 52.5 degrees -- in a quarter century, according to statistics compiled by local meteorologist John Papineau at the Anchorage office of the National Weather Service.

As the agency's climatologist for Alaska, he's often asked these days why that happened.

Similar to his colleagues at the climate prediction center, Papineau traces part of the answer to ocean temperatures, which are currently more than a half-degree colder than normal off the west coast of South America -- a condition scientists call "La Nina" (the meteorological opposite of "El Nino," when sea temperatures there are warmer than normal).

Besides changing weather patterns all across North America, a persistent La Nina also tends to cool sea temperatures off the coast of Alaska, which can lead to the creation of a massive high-pressure ridge in the center of the Bering Sea.

When that happens in winter, the ridge can force the Alaska-bound polar jet stream to bend north, where it further cools before swinging back south through the Interior of Alaska, trailing Arctic air. In the summer, the same high-pressure ridge in the Bering Sea can prompt the jet stream to pummel Anchorage with clouds.

"So basically we get more storms in the Gulf of Alaska during the summer and we produce more southerly flow of clouds -- which then results in cooler temperatures in Anchorage," Papineau said.

The climate prediction center, which posts long-range forecasts on its Web site on the third Thursday of each month, began forecasting Alaska's brutal early January -- based on the winter version of that scenario -- more than a month ago.

"Once you get the ocean playing along with the atmosphere, it kind of gives you some level of persistence, and now we expect (colder than normal Alaska temperatures) to last through the winter and probably through some of the early part of spring," Halpert said.

Specialists who focus solely on the ups and downs of the El Nino/La Nina phenomenon anticipate the eastern South Pacific Ocean to warm slightly in late spring, as the sea temperature index there enters a neutral phase.

That might allow Anchorage residents to once again enjoy balmier summer days, like the nine summers from 1999 to 2007, which averaged 27 days each when the temperature reached 70 degrees -- compared to the summer of 2008, which recorded only two -- according to local weather service records.

Or it might not.

The long-range temperature forecasts are only conservative statements of probability, Halpert said. They aren't certainties. And the one predicting Alaska's warmer-than-normal June-July-August period five and a half months before it arrives only says the chances of that happening are 40 percent.

Which doesn't sound very confident, even though the center says it's more probable than normal temperatures occurring in Anchorage this coming summer (a 33.3 percent chance) or colder than normal temperatures (a 26.7 percent chance).

"There's a lot of speculation that goes into these forecasts," Halpert said. "That's one reason why we update them monthly. We don't take one shot at it and live with it for the year."

On the other hand, if the South Pacific surprises everyone and grows cooler rather than warmer this spring -- thereby developing a strong La Nina -- then all bets are off, he said. And Alaskans better start battening the hatches.