El Niño Snows in DC But Not Pittsburgh

Snow on sweetgum seed balls, 17 Dec 2020 (photo by Kate St. John)

27 November 2023

Last week a friend remarked on the wide variety of winter forecasts being touted for Pittsburgh from “Swamped With Snow” to “No Skis in Our Forecast.” How could the predictions be so different? I think it’s the Beltway effect.

Right now the world is in an El Niño year of warm sea surface temperatures in the central and eastern Pacific at the equator and along the coasts of Ecuador and Peru.

Sea surface temperatures during 1997 El Niño (map from Wikimedia Commons)

According to Wikipedia, this warming causes a shift in the atmospheric circulation with rainfall becoming reduced over Indonesia, India and northern Australia, while rainfall and tropical cyclone formation increases over the tropical Pacific Ocean. El Niño seriously affects South American weather and ripples out to North America as well. The U.S. seasonal outlook, Dec 2023 to Feb 2024, shows higher temperatures in the north and wetter weather in the south this winter.

Seasonal temperature and precipitation outlooks for the U.S., Dec 2023-Feb 2024 (maps from NOAA)

Of course this affects snowfall. El Niño’s winter history in 1959-2023 shows more snow in some places (blue color) and a lot less in others (brown color). Interestingly, Pittsburgh is in the Less Snow category while Washington, DC has More Snow than usual.

Snowfall during all El Niño winters (January-March) compared to the 1991-2020 average (after the long-term trend has been removed). Blue colors show more snow than average; brown shows less snow than average. NOAA Climate.gov map, based on ERA5 data from 1959-2023 analyzed by Michelle L’Heureux.

News organizations have a big presence in the DC Beltway area and write stories for the region. Some weather stories originate there and cross the Appalachians but when the news gets to Pittsburgh it might not apply to us. The typical example is when 2 feet of snow are forecast for D.C. and hardly any falls here. I think of this as the (DC) Beltway news effect.

So when we hear dire predictions for Pittsburgh’s winter this year I plan to wait rather then worry. My guess is that we’re likely to have rain.

Raindrops on twig (photo by Kate St. John)

I sure hope the temperature doesn’t hover near freezing when it rains. Fingers crossed that we’ll be fine.

Glaze ice in Pittsburgh (photo by Kate St. John)

Read more about snow and El Niño at NOAA’s S(no)w pain, S(no)w gain: How does El Niño affect snowfall over North America?

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