The presence of El Niño is no secret, so we can openly discuss its effects. The Climate Prediction Center officially announced the arrival of El Niño on June 8, although its presence was already evident. El Niño refers to the irregular warming of a specific region in the equatorial Pacific Ocean. Its name, meaning “Little Boy” in Spanish, originated from its initial observation near Christmas along the coast of Peru centuries ago. Conversely, La Niña, the cooling of the same waters, was not named until the 1980s and lasts for three years until early spring. La Niña was a major factor contributing to the mild winter we recently experienced.

When discussing the potential impacts of El Niño, it is crucial to differentiate between global and local effects. Climate experts are engaged in intense discussions about El Niño’s influence on already high global temperatures, potentially resulting in extreme heat waves and a new global average temperature record. El Niño does indeed inject heat into the atmosphere, and global temperatures tend to rise during its occurrence. With consecutive years of near-record global average temperatures and the current year on track to surpass them, it is anticipated that the new El Niño, both this year and possibly in 2024, will lead to new record peaks in global average temperature.

However, heat is not uniformly distributed throughout the global atmospheric system, which explains why projections of record global average temperatures and widespread heat waves may not always manifest identically in local areas. When examining continental or regional weather patterns more closely, some regions may frequently experience hot high-pressure ridges, while others may encounter cooler low-pressure troughs between them.

In North America, El Niño-related patterns generally result in warmer highs over northern latitudes and cooler troughs to the south. We have witnessed this phenomenon in May and early June, exemplified by a recent influx of smoke-laden chilly air from Canada, which even caused sporadic frost in parts of Southwest Virginia.

The increase in global average temperatures occurs because the “heat dome” highs are generally larger and hotter than in the past, offsetting the cooler temperatures in the troughs when considering the overall figures. However, if a specific location experiences more troughs than ridges during a particular season or year, the local average temperature may not follow the same trend or intensity as the global average. While there are no definitive outcomes for our region regarding El Niño’s impact, there are loose correlations between previous El Niño episodes and certain weather patterns that provide some insight into what we might expect in the months ahead.

Likely, a wet winter lies ahead. Historical data since 1950, when El Niño Southern Oscillation data became more reliable, indicates that the winter of 1997-98, during an El Niño period, holds the record for the wettest conditions in Roanoke, Lynchburg, and Danville, and ranks as the third wettest in Blacksburg. Other El Niño winters, such as 1986-87, 2002-03, 2009-10, 2015-16, and 2017-18, often rank among the top wettest winters at various regional locations.

El Niño exhibits a strong correlation with an enhanced subtropical jet stream that predominantly flows from west to east across the southern United States, particularly during the cooler months. This pattern tends to bring moisture-laden systems across the southern states, drawing more moisture from the Gulf of Mexico.

In the case of Virginia, our region typically lies at the edge of the wetter zone in the southern United States during El Niño events. While the Ohio Valley to the west tends to be drier, most of the Old Dominion leans toward wetter conditions in El Niño winters. However, the extent to which this precipitation manifests as snow is a separate matter, which will be discussed in subsequent sections.

Contrary to widespread belief, El Niño does not necessarily lead to cold or snowy winters in our region. However, based on past trends, it can significantly increase the likelihood of at least one major snowstorm occurring during the winter. In the past 25 years, five snowstorms that dumped a foot or more of snow on half or more of the Southwest/Southside Virginia region occurred during El Niño winters. Exceptions to this trend include February 2014, which took place during a neutral equatorial Pacific pattern that was neither El Niño nor La Niña. Other snowstorms, such as the ones in January 1966, December 1969, February 1983, and the extremely cold winters of 1976-77 and 1977-78, also coincided with El Niño. These patterns often combine a swift, moisture-rich subtropical jet stream across the southern U.S. with blocking high pressure to the north, resulting in prolonged wintry conditions or intermittent setups amidst a mild, rainy winter.

To predict whether the upcoming winter will be colder and snowier overall, more information about the intensity and alignment of El Niño (centered more east or west), potential interactions with other atmospheric patterns, and the progress of early-season snow cover across Siberia and Canada will be needed. These factors will become clearer by fall.

In an interesting turn of events, last week witnessed patches of frost in Carroll and Floyd County, along the Blue Ridge, extending westward past Interstate 77 into the southwest corner of the state. Although not widespread, these localized occurrences disappointed a few farmers and gardeners. Notably, Burke’s Garden in Tazewell County experienced an official low of 33 degrees on June 9, while Copper Hill in Floyd County recorded lows of 39 and 37 on June 8 and 9, respectively. Sparta, located just across the state line in Alleghany County, North Carolina, reached a frigid low of 29 degrees on Friday morning.

Most areas in Southwest and Southside Virginia had temperatures in the 40s during both mornings, with some urban areas experiencing lower 50s. The unseasonably cool air resulted from the southward flow generated by the rotation of a strong low-pressure system near Maine. This system also carried dense smoke from forest fires in Quebec and Ontario, causing smog in New York City and obscuring ridgelines across much of Virginia.

The stalled low-pressure system in the northeast U.S. and southeast Canada, which produced the blocked pattern, has now dissipated, and a more typical west-to-east airflow has resumed in our region, occasionally angling northwest-to-southeast. This has helped disperse most of the smoke from last week, although occasional traces may persist in the upper atmosphere as long as the fires continue in western and eastern Canada, likely until next winter.

Currently, we are experiencing more typical June temperatures, with many locations expecting highs exceeding 80 degrees over the next few days, along with periodic chances of showers. Several areas in our region are becoming dry, but there are indications of more widespread rainfall occurring in the early to middle part of next week.