La Nina returns for another winter.

                La Nina has again emerged for the 2017-2018 winter season. The official forecast is greater than 60% that it will persist through the season and into spring. Much like last year, La Nina appears to be weak once more.

                What exactly is La Nina, and what are the impacts for the Mid-Atlantic region? You’re probably familiar with its counterpart, El Nino. This phenomenon occurs when equatorial ocean temperature is warmer than average.

With La Nina, the opposite occurs. Ocean surface temperature is cooler than average around the equator. The cooler the temperature, the stronger the La Nina event and the larger the impact.

La Nina’s effect on the Great Lakes area generally leads to warmer than average temperatures, with above average precipitation. This outcome was certainly true for last winter. Temperatures across the area were mild. Precipitation was well above average, though much of it was in the form of rain.

Similar to the previous year was the winter of 2011-2012. Temperatures across the eastern U.S. were well above average. It was a stormier winter season than most as well, with several severe weather events occurring as far north as Indiana in January and February.

Exceptions do occur, though. The 2010-2011 winter season was in a strong La Nina. That season was noteworthy for four blizzard events across the Midwest and northeast. The term ‘Snowpocalypse’ became widespread in the media and popular vernacular.

What can we expect for this winter? It’s still too early to tell for sure. Forecast models for the coming week are pushing a cold airmass into the northeast. Highs could average around 30 degrees beginning midweek and into next week. But these patterns can and do change. Time will tell what the heart of winter brings.

Never let your guard down, though. Prepare for winter to the best of your ability. Have warm, insulated clothing on hand. Keep snow shovels and ice melt ready for sidewalks and driveways. Make sure your car is in shape with good tires. Winter weather has been responsible for over 1800 deaths on the road in the past 10 years.

Finally, take weather forecasts seriously. Winter weather may be more difficult to predict with pinpoint accuracy, but a little knowledge goes a long way.