WSI, a division of The Weather Company, issued their January through March 2016 outlook update, and both forecast temperatures and precipitation have the fingerprints of the current strong El Niño, the strongest in 18 years, all over them. The forecast includes the potential for a significant cold snap in parts of the central and eastern states starting in the middle portion of January.

Stronger El Niños typically exhibit their peak influence on North America's weather pattern during the core winter months.

Keep in mind, however, there are several other factors in the atmosphere, operating on shorter time scales, that can, at times, oppose the overall three-month trend.

We'll go into more detail on those patterns following the outlooks a bit later. First, let's take a look at the latest outlooks for average temperature and total precipitation across the U.S. for January through March 2016.

These predictions do not project when and where individual storms may occur. An individual cold front or an upper ridge of high pressure can lead to a brief period of colder or warmer weather, respectively, that bucks the overall three-month trend. The same front or area of high pressure can bring a brief period of enhanced precipitation or dry spell that may or may not be indicative of the overall trend that is forecast.

Temperatures

For the first three months of 2016, WSI says the best chance of colder-than-normal temperatures lies in roughly the southern half of the Lower 48 states, from Southern California into the Southern Plains, Deep South, Florida and the Carolinas.

Meanwhile, a large swath of the western and northern United States from northern California into the Pacific Northwest eastward into the Midwest, Great Lakes and Northeast is expected to be warmer than normal, overall.

However, there's a January catch.

"We expect a 'tale of two months', with a cold-West, warm-East first half of the month, followed by a reversal during the back half of the month towards potentially much colder eastern U.S. temperatures," wrote Dr. Todd Crawford, WSI chief meteorologist, in their outlook released Friday.

Interestingly, one factor in this pattern reversal may have been brought about by an Icelandic storm that tugged above-freezing air to the North Pole between Christmas and New Year's Eve.

"The rapid and unexpected destruction of the tropospheric polar vortex, via the historically strong North Atlantic storm this week, has thrown a significant monkey wrench into the January forecast," said Crawford.

(MORE: Icelandic Storm Sent Warm Air to the North Pole )

Specifically, the more "blocked up" the upper-level flow is in the higher latitudes, the more likely cold air is going to be forced south into the U.S. The stronger and more persistent the blocking, the longer the cold air will stick around.

Crawford said whether the colder East pattern relents later in January is uncertain, as upper-atmospheric blocking, such as is forecast for mid-January, often lasts longer than numerical models suggest.

"It would not surprise us if the second half of the month was quite cold across much of the East, and there are clearly cold risks to our forecast."

(MORE: Warmest December on Record For Hundreds of Cities )

Beyond January, the basic warmer-than-average North, but colder-than-average South outlook still holds.

In a typical strong El Niño winter, a warm South in December eventually transitions to a colder-than-normal January, February and March, while the northern tier of states remains relatively mild, by winter standards.

But that's not always the case. The winters of 1972-73 and 1965-66 were considerably colder in much of the northern tier of states during those strong El Niños, and the winter of 1957-58 was very cold in the Northeast.

Precipitation

NOAA expects January through March 2016 to trend wetter than usual over much of the southern tier of the nation, from California into the Desert Southwest to the southern and central Plains, as well as the Gulf Coast and Southeast coast, including Florida.

Parts of the Northeast seaboard from the Mid-Atlantic states into southern New England, may also see more precipitation than a typical winter.

Conversely, a relatively dry winter is expected over parts of the Pacific Northwest, northern Rockies and into the far northern Plains, Great Lakes and Ohio Valley.

This precipitation outlook owes to the typical dominance of the subtropical or southern branch jet stream during a strong El Niño winter, bringing more frequent and vigorous low-pressure systems along the nation's southern tier.

(MORE: El Niño and Seasonal Snowfall | Your Typically Snowiest Month )

This should at least deliver a significant dent in California's exceptional drought, but even a strong El Niño winter doesn't assure that.

As we discussed in an early December article about the winter outlook , one of the five previous strong El Niño seasons was drier than average in the Golden State (1965-66).

The aforementioned subtropical jet stream usually brings an increase in Pacific storms to California in January and February.

Conversely, drought may either hold steady or expand during the winter in the northern Rockies and northern High Plains, thanks to persistent warmth and expected drier conditions.

El Niño Not the "Be-all and End-all"

The current strong El Niño has peaked, but its influence on the atmopshere and subsequent temperature and precipitation impacts is most strongly felt in the northern hemisphere winter months.

However, three variables, in addition to El Niño, could play an important role in early 2016, including the North Atlantic Oscillation, the Arctic Oscillation and the Madden-Julian Oscillation. These features can be difficult to forecast more than a few weeks in advance.

The North Atlantic Oscillation (NAO) basically describes the degree of blocking of the jet stream over the North Atlantic Ocean, frequently in the vicinity of Greenland. The NAO's negative phase features high pressure aloft blocking the west-to-east flow of the jet stream, forcing it to buckle south over the eastern U.S., ushering in prolonged cold air. The positive phase is just the opposite; no blocking means Canadian cold air mainly drains west-to-east across the content, not plunging deep into the U.S.

The Arctic Oscillation is a climate pattern characterized by the strength of counterclockwise winds around the Arctic. Its positive phase confines cold air to the polar regions, while its negative phase is associated with cold air penetrating farther south, as well as an increased chance of nor'easters.

(MORE: Winter Storm Names 2015-2016 | The Science Behind Naming Winter Storms )

The Madden-Julian Oscillation is associated with variations in tropical thunderstorm activity (convection) and is characterized by an eastward-moving pulse of atmospheric features affecting cloud formation, precipitation and pressure patterns. This pulse circles the globe roughly once every one to two months. In turn, the jet streams over the North Pacific and South Pacific can be impacted during the winter due to large-scale changes in tropical convection. This can contribute to blocking activity which impacts the amount of precipitation across the Pacific Northwest.

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