By Corey Davis, NC State Climate Office
It’s said that no two snowflakes are alike — and science backs that up — but could we see two winters following the same template in back-to-back years?
Early signs among the ocean and atmosphere are showing similar setups to last winter, which was dry overall but with multiple wintry events affecting all parts of the state.
For the 14th year in a row on the Climate Blog, we’ll peruse the clues in the ENSO pattern, several other atmospheric signals, and comparable past years to inform our winter outlook for North Carolina.
Another La Niña Lined Up
The most obvious similarity to last winter is the state of the El Niño/Southern Oscillation – a pattern characterized by the cyclical warming and cooling of the water in the equatorial Pacific Ocean.
Rather than shifting away from last year’s La Niña pattern, sea surface temperatures in that region have remained cooler than normal over the past 12 months, setting us up for a second La Niña winter in a row.
That’s not particularly unusual. In fact, about half of all La Niñas since 1950 have been followed by another one in a so-called double dip event. We recently even had a triple dip with three consecutive La Niñas in 2020-21, 2021-22, and 2022-23.
La Niña is typically associated with a weaker and northward-shifted jet stream over the continental United States, which puts North Carolina south of the prevailing storm track to make us generally warm and dry.
There’s some historical evidence that La Niña’s impacts in the US – particularly to our precipitation patterns – tend to be more pronounced in a double-dip winter. However, it’s worth noting that this is expected to be a weak La Niña overall, just as it was last winter.
One measure of ENSO’s strength, the Oceanic Niño Index (ONI), looks at sea surface temperature anomalies within a small region of the central Pacific, and over the latest three-month period from August through October, the ONI was 0.5°C below normal – right at the La Niña threshold.
Last winter, sea surface temperature anomalies in the ENSO monitoring region were 0.6°C cooler than normal. Current model forecasts show a similar peak this winter of -0.6 to -0.7°C.
Chances for Cold (and Snow?)
A weaker La Niña tends to have a looser grip on the global atmosphere, which gives chances for other patterns to shape our weather at times throughout the season.
We saw that last winter when the usual La Niña-driven jet stream ridging pattern gave way to troughing and several blasts of cold air in January, setting the stage for our first statewide snow events in almost three years.
And we had another example of that this month, when an Arctic cold front brought widespread below-freezing temperatures and even some light snow accumulations in the early morning hours on November 11.
While it’s tough to predict exactly when any other cold spells may occur over the next three months, it does appear that the atmospheric gates to the Arctic will continue to swing open in the coming weeks.
The upper-level winds in the polar jet stream are expected to weaken during the week of Thanksgiving as part of a Sudden Stratospheric Warming event. Despite the name, this sort of pattern is usually linked with cooler weather at the surface as the polar vortex splits up and unleashes shots of cold air unusually far south.
This upcoming event should bring a chilly start to December across the Northern Plains, with potentially a more brief cooldown at some point in North Carolina. This setup could also be a signal that we won’t be locked into warm weather all winter long.
Another atmospheric pattern worth watching is the Madden-Julian Oscillation (MJO), which describes the eastward movement of moisture around the global tropics. As with ENSO, this pattern can have far-flung impacts, including in our region.
The MJO is classified into eight different phases corresponding to the location of that tropical moisture as it traverses the world every 30 to 60 days. That cyclical behavior also gives it a degree of predictability a month or so in advance.
Notably, current forecasts show the MJO entering phase 8 by mid-December. That’s typically associated with cooler temperatures in the eastern US, while phases 1 and 2 that often follow tend to be cooler and wetter than normal across the Southeast.
Before you get your hopes up about anything cold and wet by late December, it’s worth remembering that these impacts aren’t set in stone – only a general trend – and it takes a very particular alignment of more localized patterns for us to see any precipitation in a frozen form. But it’s at least another sign that not all patterns are pointing in the same warm and dry direction as La Niña would suggest.
Hints from Our History
Historically, there have been 13 weak La Niña winters – with an ONI between -0.5 and -0.9°C – since 1950, including last year. Among those, 7 were warmer than normal and 11 were drier than normal in North Carolina.
Digging deeper into those years, the early-winter months were largely toss-ups in terms of temperature: 7 of those 13 winters were warmer than the historical average temperature in December, and 6 were warmer than average in January.
However, February was warmer than average in 11 of those 13 winters, which lines up with a recent trend in our climate; 9 of the past 10 Februarys have been warmer than normal in North Carolina, including our 2nd-warmest February on record amid another weak La Niña in 2023.
Out of those winters, December was generally near-normal in terms of precipitation; only 4 of those 13 Decembers ranked in our state’s top 20 wettest or driest on record dating back to 1895. Nine of the 13 weak La Niña winters were drier than normal in January, and we also had a dry February in 9 of those years.
The past four weak La Niña winters – in 2000-01, 2008-09, 2022-23, and 2024-25 – were each preceded by a dry fall, and three of those four winters finished with drought present in parts of the state, hinting that our current drought may stick around for a few more months.
When comparing past years, it’s tricky to read too much into snow totals since it only takes one big event to bring a season’s worth of snowfall. For what it’s worth, there were several notable winter storms among these recent weak La Niña winters. The winter of 2000 started with a significant coastal snowstorm on December 2, while we saw long-lasting statewide “snow droughts” come to an end in both January 2009 and January 2025.
Our Winter Outlook
Piecing these clues together, we see a few likely outcomes this winter, along with some other stories to watch with our weather over the next three months.
True to La Niña’s typical impacts, we’re expecting the winter will be drier than normal overall. The Climate Prediction Center likewise shows a lean toward below-normal precipitation across the Southeast, along with La Niña’s telltale wetter signal over the Ohio Valley due to the more northerly storm track.
While La Niñas are often warmer than normal as well, we’re not as confident in calling for prevailing warmth. Like last year, when a frigid January was balanced by warmer weather in December and February to yield near-normal seasonal temperatures, we think this winter could also be a temperature tug-of-war, particularly between potential cold spells early and a likely warm-up by February.
While snow is never a guarantee in North Carolina and La Niña events often reduce those odds even further, we do envision enough cold air creeping in to generate some opportunities for snow. But barring a major event, we anticipate below-normal snowfall for the entire season, as was the case last year in places like Charlotte, Raleigh, and Greensboro.
The bigger precipitation story may be the continuation of drought, as current rainfall deficits dating back to mid-August range from 4 to 10 inches in most areas, and a dry winter would not make much of a dent in those.
However, with lower evaporation rates and water demands during our cool season, we could at least see a reduction in drought impacts, especially if we receive semi-regular precipitation to top off our struggling streamflow and soil moisture levels.
Finally, if these patterns and predictions pan out, then we expect a sense of déjà vu across the state, because that would mean this winter followed in the footsteps of the last one in a bit of un-snowflake-like symmetry.
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