The western half of the continental U.S. and central and northern Alaska could be in for a warmer-than-average winter, while most of Florida might be colder-than-normal December through February, according to NOAA's annual Winter Outlook.
Forecasters with NOAA's Climate Prediction Center say a wavering El Niño, expected to have developed by now, makes this year's winter outlook less certain than previous years.
"This is one of the most challenging outlooks we've produced in recent years because El Niño decided not to show up as expected," said Mike Halpert, deputy director of NOAA's Climate Prediction Center. "In fact, it stalled out last month, leaving neutral conditions in place in the tropical Pacific."
When El Niño is present, warmer ocean water in the equatorial Pacific shifts the patterns of tropical rainfall that in turn influence the strength and position of the jetstream and storms over the Pacific Ocean and United States. This climate pattern gives seasonal forecasters confidence in how the U.S. winter will unfold. An El Niño watch remains in effect because there's still a window for it to emerge.
Other climate factors can influence winter weather across the country. Some of these factors, such as the North Atlantic Oscillation, a prominent climate pattern, are difficult to predict more than one to two weeks in advance. The NAO adds uncertainty to the winter outlook in the Northeast and Mid-Atlantic portions of the country.
Areas ravaged by extreme drought over the past year are unlikely to see much relief from drought conditions this winter.
In the 2012 U.S. Winter Outlook (December through February) odds favor:
-Warmer-than-average temperatures in much of Texas, northward through the Central and Northern Plains and westward across the Southwest, the Northern Rockies, and eastern Washington, Oregon and California, as well as the northern two-thirds of Alaska.
-Cooler-than-average temperatures in Hawaii and in most of Florida, excluding the panhandle.
-Dryer-than-average conditions in Hawaii, the Pacific Northwest and Northern California, including Idaho, western Montana, and portions of Wyoming, Utah and most of Nevada.
-Dryer-than-average conditions in the upper Midwest, including Minnesota, Wisconsin, Iowa and northern Missouri and eastern parts of North and South Dakota, Nebraska, Kansas, and western Illinois.
-Wetter-than-average conditions across the Gulf Coast states from the northern half of Florida to eastern Texas.
The rest of the country falls into the "equal chance" category, meaning these areas have an equal chance for above-, near-, or below-normal temperatures and/or precipitation.
This seasonal outlook does not project where and when snowstorms may hit or provide total seasonal snowfall accumulations. Snow forecasts are dependent upon the strength and track of winter storms, which are generally not predictable more than a week in advance.
Temperatures will be a few degrees below average across the UK this weekend, but largely dry conditions are expected.
After no rain for almost a month, Santiago braces for rain early in the week. Cool air follows, spreading into Chile, Argentina and Uruguay mid-week.
There is a significant chance that Jimena will turn back toward Hawaii and threaten the islands during the second week of September.
An unusually strong push of cool air for early September will move southward along the Atlantic Seaboard into the Labor Day weekend before July-like heat returns by next week.
Steering winds could take Ignacio, as a remnant storm, into the southeastern arm of Alaska or British Columbia during the middle days of next week.
Strong thunderstorms will roll across the Upper Midwest while rain and strong winds roar through the Northwest this weekend.
Los Angeles, CA (1988)
110 degrees -- all-time September record.
Washington, DC (1939)
"Once in a hundred-year rainstorm" 4.40 inches in 2 hours at the Washington Zoo.
Minneapolis, MN (1941)
Tornado - 5 dead - $450,000 damage.