AshevilleWX 2020-2021 Winter Weather Outlook

Each year here at AshevilleWX we do our best to put out a reasonable forecast about what you can expect during winter, based off of several factors. Most of this forecast is rooted in historical data and conclusions are reached through data comparison. Once we denote similarities of how a particular year is setting up, we can compare this data to data from years past to create a Winter Weather Outlook. This is merely a long range forecast though, and there is great uncertainty as usually with exactly how winter will unfold here in the mountains of WNC. Below you can find my 2020-2021 Winter Weather Outlook.

Seasonal Snowfall 20’-21’ Projections

Boone: 28”-35”

Asheville: 6”-8”

Charlotte: 2”-3”

Greensboro: 4”-6”

Raleigh: 3”-5”

Wilmington: 1”-2”

Why Less Than Average Snowfall For WNC?

There are a couple of factors that have lead me to forecast less than average snowfall for WNC this year, but the main reason is due to a moderate to strong La Nina setting up. What is La Nina? This is when cooling happens in the Nino region of the Pacific Ocean. The Nino region is observed on a regular basis by multiple sensors that monitor water temperatures. This area is where weather is generated for portions of the United States. If this region is warmer than normal then El Nino is consider to be in place. If the region is cooler than normal then La Nina is considered to be occurring. Historically, we see wetter conditions during El Nino events here in WNC. This means that warmer than normal temperatures in the Nino 3.4 region equates to wetter winter conditions in the Mountains of WNC. On the other hand, a La Nina would mean that temperatures in the Nino 3.4 region of the Pacific Ocean are cooler compared to the average. Historically during La Nina years, less precipitation has moved through WNC during winter time frames. With less activity in the key region, storms and Gulf Lows will be limited around the South. Strong cold shots are also possible with La Nina season, but I am leaning more towards a mild winter compared to a bitter cold one. That still remains to be seen though.

Moderate To Strong La Nina Setting Up

We have a moderate to strong La Nina setting up in the key Nino region where observations are taken. That means that cold water is pooling up in this region, and sea surface temperatures are falling below average. Therefore, limited storm development is expected to occur along the Equator and that means less precipitation moving through the Southeast. This is strictly based off of historical data. Below you can see what a typical La Nina looks like when observing sea surface temperatures.

What To Expect Here In WNC?

Evan Fisher has produced a great graphic that details out the amount of snowfall we received here in WNC each Moderate or Strong La Nina year. As you can see below, there is great variation among average snowfall each year during moderate & Strong La Nina years.

Here is also a map that shows the combined average of snowfall each year during Moderate & Strong La Nina Winters. As you can see, we are working with limit data to compare with only 11 data points of comparison. Moderate to Strong La Ninas are somewhat rare, which is why there is great uncertainty with this forecast.

Forecast

I posted this map above, but it is worth revisiting. I believe that Northwest Flow Snowfall will dominate totals this year in the NC Mountains, with close to average yearly snowfall totals being possible. Throughout the years, Northwest Flow has been the most consistent with providing snow events to the border counties.. and during this La Nina event I believe that sweeping arctic fronts this winter will bring several chances for Northwest Flow. That is why I have place most elevations above 3500’ in WNC at 80%-100% of normal in my projection map. Moving into the valley areas of WNC where snowfall totals are typically achieved by strong Gulf Low pressures, I have placed 60%-80% of normal snowfall. With limited storms moving in from the Gulf region, I think chances will be limited for a large snowstorm across the Southeast. That of course does not mean that one is not possible, history just shows that WNC and NC in general receive less precipitation during La Nina years.

Moving on to the Piedmont area, I am projecting 60%-80% of average snowfall for the areas like Greensboro & Charlotte. Each year these locations tend to receive their yearly snowfall totals from Gulf Lows, and I am of the opinion that those will be limited this year. Things like backdoor frontal passages will be where snowfall is picked up in the Piedmont, but the chances for Gulf Lows appear to be less compared to El Nino years.

The Raleigh area will be an area of transition in my opinion. I believe that we will see a strong cold shot or two this year, and this will be where locations along the Coast of NC see their chance for snow. During La Nina seasons, suppression of storms can lead to strong cold meeting with a meandering low pressure along the coast. It is my opinion that we will see one of these type storms develop this winter, and locations along the coast will receive 100%-120% normal snowfall. The Raleigh area, being on the fringe of these events, as well benefiting from backdoor cold fronts and placing that location in my 80%-100% yearly snow average zone.

Model Data

I have sourced a couple of long range models as well to illustrate the outlook on snowfall for this winter. Snow lovers will not like these maps, but they are a good indicator and were somewhat accurate last year when I made my forecast for below normal snowfall for the Asheville area. These maps were all provided by https://www.bennollweather.com.

Model Super Blend

European Model Snowfall Forecast By Month

UKMET Snowfall Forecast By Month

Conclusion

This year across WNC, snowfall averages will vary greatly. Based off of a super blend of knowledge, I forecast that WNC will see slightly below normal snowfall, with near average temperatures throughout the season. Conditions could be fairly dry at times with limited forcing from the Pacific, but one Gulf Low that threads the needle will be all it takes to bust my forecast. Please take this forecast with a grain of salt, and know that these forecast are mainly for fun and enjoyment. Know the winter weather is extremely unpredictable, and each year a new precedence can be set. Use this article for fun, but don’t use it as spoken word because no winter forecast should be taken as certainty.

-Meteorologist Hunter Ward