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Winter of extremes forecast for U.S.

The Pacific Northwest should
brace for a colder and wetter than average winter, while most of the South and
Southeast will be warmer and drier than average through February 2011,
according to the annual Winter Outlook released today by NOAA’s Climate
Prediction Center. A moderate to strong La Niña will be the dominant climate
factor influencing weather across most of the U.S. this winter.

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La Niña is associated with cooler than normal water
temperatures in the Equatorial Pacific Ocean, unlike El Niño which is
associated with warmer than normal water temperatures. Both of these climate
phenomena, which typically occur every 2-5 years, influence weather patterns
throughout the world and often lead to extreme weather events. Last winter’s El
Niño contributed to record-breaking rain and snowfall leading to severe
flooding in some parts of the country, with record heat and drought in other
parts of the country. Although La Niña is the opposite of El Niño, it also has
the potential to bring weather extremes to parts of the nation.

“La Niña is in place and will strengthen and persist through
the winter months, giving us a better understanding of what to expect between
December and February,” said Mike Halpert, deputy director of the Climate
Prediction Center – a division of the National Weather Service. “This is a good time for people to review the outlook and begin preparing for what winter may have in store.”

“Other climate factors will play a role in the winter
weather at times across the country,” added Halpert. “Some of these factors,
such as the North Atlantic Oscillation, are difficult to predict more than one
to two weeks in advance. The NAO adds uncertainty to the forecast in the
Northeast and Mid-Atlantic portions of the country.”

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Regional highlights include:

Pacific Northwest:
 
Colder and wetter than average. La Niña often brings lower than
average temperatures and increased mountain snow to the Pacific Northwest and
western Montana during the winter months, which is good for the replenishment
of water resources and winter recreation but can also lead to greater flooding
and avalanche concerns. 

California and the
Southwest:
Warmer and drier than average. This will likely exacerbate
drought conditions in these areas. All southern states are at risk of having
above normal wildfire conditions starting this winter and lasting into the
spring. 

Northern Plains:
Colder and wetter than average. Likely to see increased storminess and
flooding.

Southern Plains, Gulf
Coast States and Southeast:
Warmer and drier than average. This will likely
exacerbate drought conditions in these areas. All southern states are at risk
of having above normal wildfire conditions starting this winter and lasting into
the spring.

Florida: Drier
than average, with an equal chance for above-, near-, or below-normal
temperatures. Above normal wildfire conditions.

Ohio and Tennessee
Valleys:
Warmer and wetter than average. Likely to see increased storminess
and flooding.

Northeast and
Mid-Atlantic:
Equal chances for above-, near-, or below-normal temperatures
and precipitation. Winter weather for these regions is often driven not by La
Niña but by weather patterns over the northern Atlantic Ocean and Arctic. These
are often more short-term, and are generally predictable only a week or so in
advance. If enough cold air and moisture are in place, areas north of the Ohio
Valley and into the Northeast could see above-average snow. 

Central U.S.: Equal
chances of above-near-or below normal temperatures and precipitation.

Hawaii: Drier than normal through November, then wetter than
normal December through February. Statewide, the current drought is expected to
continue through the winter, with several locations remaining on track to
become the driest year on record. Drought recovery is more likely on the
smaller islands of Kauai and Molokai, and over the windward slopes of the Big
Island and Maui.

Alaska: Odds
favor colder than average temperatures with equal chances of above or below
normal precipitation. The interior and southern portions of the state are
currently drier than normal. A dry winter may set Alaska up for a greater
chance of above normal wildfire conditions in the spring.

This seasonal outlook does not project where and when
snowstorms may hit or total seasonal snowfall accumulations. Snow forecasts are
dependent upon winter storms, which are generally not predictable more than
several days in advance.

By James Peronto, National Oceanic and Atmospheric Administration

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