The WUSA 9 Weather Team is predicting near average temperatures and above average snowfall this year. The biggest driver to our winter weather will be an El Niño.
What Is El Niño?
El Nino is one phase of the El Niño Southern Oscillation (ENSO), a climate cycle driven by ocean temperatures in the eastern Pacific Ocean near the Equator, very close to South America. During an El Niño, a warm pool of water develops in this location, which drives a change in the weather patterns in the United States. The opposite phase of ENSO is called La Niña, in which cooler-than-average temperatures are located in the equatorial Pacific.
Graphic: What Happens In An El Niño winter. App users click here.
What Happens In An El Niño Winter?
During an El Niño winter, the warm ocean waters in the equatorial (near the equator) eastern Pacific fuel an intensification of the southward shift of the jet stream. This means the storm track pattern across the U.S. is very active over the south. That storm track will curve northward over the Atlantic. Based on this, a few coastal storms will be possible.
Graphic: Impacts In An El Niño winter. App users click here.
What Does This Mean For DC?
El Niño winters can be good news for snow lovers in the metro area, depending on strength. Weak to moderate El Niños usually result in above-average snowfall and precipitation with below-average temp but fewer Arctic outbreaks of cold air. But strong El Niños are almost like flipping a coin -- out of the past 7 strong El Niños, 3 have resulted in below-average snowfall and 4 have resulted in above-average snowfall.
Graphic: Snowfall in DC during El Niño Winters. App users click here.
Average Snowfall in the DC Area
The graphic below shows the average seasonal snowfall across the area, based on 1981 - 2010 data. The average seasonal winter snowfall at Reagan National is just 15.4". Dulles' average snowfall is 22.0". App users click here.
The WUSA 9 2018 - 2019 Winter Snowfall Outlook
Because of the El Niño, we are forecasting the chance for a Nor'easter or two, which should translate into above-average snowfall. We are also predicting below average temperatures with fewer Arctic outbreaks. Here's how much you snow can expect by region.
Graphic: Winter Snowfall Forecast for 2018 - 2019 in the DC area. App users click here.
Region By Region Breakdown:
Southern Maryland - 10" or less
Fredericksburg, Waldorf, and Upper Marlboro - 10" to 20"
DC Metro Area, including DC, Gaithersburg, Leesburg and Fairfax - 20" to 30"
Frederick, Hagerstown, Winchester, Martinsburg and I-81 - 30" to 40"
What Does This Mean For Ski Resorts
This should be a better better season for ski resorts than the past two years, given the potential for one or two big nor'easters. We are also predicting below-average temperatures, which will be good for keeping conditions primed for snowmaking, even when it may not be snowing.
When Can We Expect The First Snow?
Topper is predicting the first snowfall of 1" or more on December 17th. The last 2 years, Topper was spot on with this prediction and it first snowed 1" in DC on the exact date of his prediction.
When Can We Expect The Most Snow?
Predicting exactly WHEN our first nor'easter or big snow of the season will fall is too difficult this far out.
