Greensboro, NC -- The leaves are showing their fall color and the temperatures have already made it quite clear that summer is over. As we make the transition from summer to fall we inevitably begin to prepare for the winter season ahead.
Coming off of a record warm summer in many places across the United States one might assume that this winter will continue to be warmer than normal. While in some locations this may be true, as a whole there are some large scale climate patterns that have shifted somewhat since the dog days of summer.
The more well known of the main winter season indicators is El Nino. Typically during an El Nino winter the Southern and Mid-Atlantic States tend to have more precipitation than normal. Temperature-wise the Southern states tend to be cooler than normal while the Mid-Atlantic remains near-normal to slightly cooler than normal. Latest indications are that we will be in a weak El Nino pattern through the majority of the winter season with a trend towards a neutral phase into spring.
Alone El Nino only tells us part of the story. Another large scale atmospheric pattern that plays a significant role in the type of winter the Triad will see is the North Atlantic Oscillation (NAO). This pattern has two main phases (positive & negative) from which it 'oscillates' between.
Most of this year the NAO has been in the negative phase, but has played a very little role in the weather this summer. The NAO has a direct influence on the jet stream which drops south during the winter months. Specifically, the negative phase of the NAO causes the jet stream to buckle and dive south which allows cold Canadian air to also dive south into the eastern United States.
This will not result in constant pipeline of cold air spilling into the eastern U.S., but will offer an elevated number of quick cold blasts. The increase is bursts of cold air will then increase the odds of snow developing in the presence of ample moisture.
A prime example of the influence of the NAO on snow in the Triad was recently seen during the winter of 2009-2010 when the NAO index reached record levels. That winter the Triad received 16.6" of snow. This total nearly doubled the 9" of snow that the Triad can expect to see in an average winter.
The presence of El Nino combined with the negative phase of the NAO leads us to believe that temperatures will be near normal this winter while snow amounts could be near, if not slightly above normal. The normal high/low temperatures in December, January and February are 50/32, 48/30 and 53/32 degrees respectively.
Winter snow totals are greatly dependent on individual storm systems that occur throughout the season. These individual storms exist on a very small scale compared to the larger scaled patterns such as El Nino and the NAO. As a result the individual systems are nearly impossible to forecast more than 7-14 days in advance.
This fact makes it very difficult to put much confidence in a forecast for exact snow totals. So, in a very general range we believe that the Triad could receive anywhere between 8"-11" of snow this winter. Keeping in mind that the actual total could be greatly altered by one snow storm occurring or not occurring.
METEOROLOGST GRANT GILMORE'S WINTER OUTLOOK BLOG
The official start to winter occurs on December 21st, but the Triad typically starts to see it's first flakes sometime in the middle of November.
Be sure to stay with digtriad.com and WFMY News 2 for the latest weather conditions and the most accurate forecast in the Triad.
WFMY News 2