It is that time of year time to look ahead to see what winter might have in store. This is one of my favorite outlooks of the year I learn a lot from the research and I hope you will too. Meteorological Winter begins December 1st and Astronomical Winter begins December 21st. For Weather and climate purposes Winter starts December 1st. Before going in-depth please keep in mind that meteorology is NOT an exact science, and climate-based meteorological outlooks are more complex than regular 5 and 7 day forecasts. I have been researching various factors that impact Winter Weather Across the South and really for the entire United States from previous Winters (analogs) to sea surface temperatures, Jet stream Patterns, Snow cover over Canada and Siberia. This year we have La Niña. El Niño and La Niña are opposite phases of what is known as the El Niño-Southern Oscillation (ENSO) cycle. The ENSO cycle is a scientific term that describes the fluctuations in temperature between the ocean and atmosphere in the east-central Equatorial Pacific (approximately between the International Date Line and 120 degrees West). La Niña episodes typically last nine to 12 months, but some prolonged events may last for years. El Niño and La Niña events occur on average every two to seven years. Typically, El Niño occurs more frequently than La Niña. La Niña events represent periods of below-average sea surface temperatures across the east-central Equatorial Pacific. Global climate La Niña impacts tend to be opposite those of El Niño impacts. In the tropics, ocean temperature variations in La Niña also tend to be opposite those of El Niño. Before I discuss winter I want to say I expect November to be below average in terms of temperatures we will have some warm days mixed in but overall we will end up colder than normal probably. I expect mid November to be quite cold. Keep in mind just because one area is showing above average temperatures or below average temperatures for the winter does NOT mean that it will be really cold or really warm the entire winter. In the south and southeast including Georgia and Alabama I think we will above average temperatures in most areas that is for the winter as a whole compared to average. I expect near average to slightly below average precipitation for much of North Georgia including Metro Atlanta. Notice on the map above North Georgia and metro Atlanta is in between the above average precipitation expected over the Ohio Valley and the well below average precipitation to the south. The areas that are expected to have below normal precipitation can still get rain and snow during the winter. Below average precipitation does not mean no rain at all or no snow. Last winter was near average to slightly below average for parts of the southeast including North Georgia (depending on specific city/area) when the temperatures from December-February were averaged. There will be SEVERAL Cold Snaps and Warm Spells in the South. Just as an example you can have really cold air in December or January and still end up having above average temperatures for the winter as a whole when the 3 months are averaged together. ALSO, it is very important to note that a region can have ABOVE Average temperatures and still have near Average snowfall or above average snowfall. I expect much of the northwestern US including Oregon and Washington state to have ABOVE AVERAGE precipitation very wet conditions and at times winter weather conditions meaning quite a bit of snow is possible especially in the Cascade mountains. The jet stream will be bringing a lot of storm systems to the Pacific Northwest and parts of the Ohio Valley and at times into the northeastern United States. When the jet stream moves down that can bring some storm systems to the deep south but moisture has to match with the cold air at just the right time to get snow. I expect drought conditions to continue in parts of eastern North Carolina, parts of Texas, parts of Florida, North Dakota, New Mexico, Arizona, and southern California. I expect some drought improvement in northern California and parts of the Pacific Northwest. The drought should improve over the winter in northern Illinois, Montana, Idaho, parts of Iowa, Minnesota and Wisconsin. Looking back over the decades a lot of our really good snows in Georgia and the southeast happened during relatively warm spells as a whole examples include January 9th 2011 the day before the snow it was 59 degrees then we had 3.7" of Snow by the next night, 2014 before a major snow/ice storm shut down Atlanta and Birmingham, temperatures were in the low 60's! One last example there are many as you can tell but before the Blizzard of 1993 temperatures was in the 70's just a few days before. The core of the cold air will be along the US/Canadian border especially for parts of Montana, Washington, North Dakota and surrounding states. I expect above average snow and in some areas even well above average snow around the Great Lakes I expect a lot of Lake Effect snow. The water temperatures on the lake can affect how much snow there is. The polar vortex is expected to be weak especially during the early part of winter. When the polar vortex is weak parts of it can break off and move south and cold air can move into parts of the lower 48 including the deep south. The North Atlantic Oscillation can impact our winter temperatures as well as the QBO and Arctic Oscillation. Some of these factors can't be predicted and indicated more than about 2 weeks in advance but they can have big impacts as to if we have colder weather or really warm weather (see more below on the maps and diagrams). Our last big winter with impacts from the Polar Vortex was winter 2014 particularly January and February 2014 when several snow and ice storms hit and we had significant cold weather at times. When our weather patterns get stuck with ridging or a trough from time to time it can also have big impacts in the winter. The troughs bring cool and (sometimes) cold air and unsettled weather and the ridges cause a big warm up. You might have heard of the southeast ridge before when a ridge develops over the southeast that can cause very warm weather and prevent cold air from moving into the southeast but on the other hand It only takes one time for cold air to match up at the right time with moisture to get a winter system. Often time during winter storms whether it be snow or ice or both there are sharp cut offs in totals. There are also sharp cut offs with the rain/snow line. Ice storms occurred during La Niña winters in Georgia in 1973, 2000 and 2005 they all were La Niña years in Georgia with big ice storms. In 2010 and 2011 also a La Niña event ALL of Atlanta and North Georgia had ABOVE AVERAGE snow and much of the south and eastern United States. La Niña events can bring a variety of weather from big snow and ice storms to severe storms and a lot of dry weather. Back in the winter of 2005 right after our last active hurricane season we only had 0.5" of snow in Atlanta. 2008 was a La Niña event and we had 1.4" of snow in Atlanta. Back in 2000 3" of snow fell in Atlanta. The latest snowfall ever to occur in Atlanta happened back on March 24th 1983 also a La Niña event when over 7" fell in the city of Atlanta with higher amounts west and north of the city. 1983 featured multiple snow storms. Our last big snow in Georgia and Alabama was December 2017 when 6 to 12" fell across much of North and West Georgia and eastern Alabama. 2017 was a La Niña event. Our last white Christmas in Metro Atlanta and North Georgia occurred during a La Niña event (2010). In 1974, 1998, 2005, 2008 and 2011 all La Niña events there was a lot of active severe weather including tornadoes. In March 2008 a tornado hit downtown Atlanta. 1974 and 2011 were both extremely active in terms of severe weather especially in the Spring. Severe weather occurs most frequently in the spring but can also occur during the fall and winter. I hope we don't but we can still experience severe weather including tornadoes even in December, January and February. As you can tell a lot has occurred during La Niña events in the past and the weather can be very variable. If anyone has any questions about the upcoming winter or any questions about weather in general feel free to message me. Regardless of what this winter brings I'll be here to keep everyone informed every step of the way No Matter The Weather I've Got You Covered!
Below is what is responsible for Most our cold air outbreaks in the US when we have a Negative NAO phase it allows cold arctic air to make it all the way down into the Southern US.
NEGATIVE NAO:
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