Significant Winter Storm To Likely Impact Parts of the Southeast Late Week

snowfall map

Synopsis

A potent shortwave will dive southeastward across the Rockies and enter the Southern Plains on Wednesday. The feature will develop into a closed low on Thursday over the Mid-South, triggering the development of a surface cyclone along the Gulf coast the same day. By early Friday, the system will reach the Georgia/South Carolina coast and trek up along the Southeast coast on Friday.

This system has a chance to bring a round of accumulating snowfall on Wednesday to far eastern Oklahoma and Kansas, northwestern Arkansas, southern/western Missouri and areas northward on Wednesday. A snowstorm will impact parts of the Southeast late Thursday into Friday, potentially including far northern Alabama and Georgia, eastern Tennessee, far southeastern Kentucky, far southern Virginia, Upstate South Carolina, and western/central North Carolina.

Forecast Discussion

As the low strengthens late Thursday into early Friday, a warm nose will attempt to works its way into southeastern Tennessee, northern Georgia, northern South Carolina, and western North Carolina. However, the passage of the strong mid-level closed will offset the magnitude of warming that otherwise would have occurred in the low levels. Strong frontogenesis across northern Georgia, upstate South Carolina, and central North Carolina could provide the necessary forcing to bring the freezing/melting level close to the surface in those areas. Evaporational cooling will also initially lower temperatures at and just above the surface. Despite lackluster cold in place across lower elevation regions in Georgia, the Carolinas, and even Southeast Tennessee, the dynamics of this storm system may actually ‘make up’ for it. Plus, the system will pass during a timeframe when temperatures are normally colder anyway (at night and early morning!).

We have quite an interesting scenario taking shape for the end of the week. The surface low on Thursday into Friday will take the classic track that favors significant winter weather across the Southeast. However, the pre-existing air mass across the region will only be marginally cold. Although colder air will get wrapped around the backside of the storm system, even it will be marginal. As a result, most regions across the Mid-South and western half of the Southeast region will likely just get a nasty, cold rain on Thursday.

Snow accumulation forecast for late-week winter storm

Snow Accumulation Forecast (Attempt #1)

  • I included a 5–10+ inch accumulation zone in the mountains of Georgia, South Carolina, North Carolina, and Tennessee, where soil temperatures are already relatively cool and low-level temperatures should be sufficient for snow (or a rain to snow transition).
  • I expect noteworthy accumulations to fall across the Cumberland Plateau, far northern Alabama, northern Upstate South Carolina, and western central North Carolina. A transition of rain to snow will likely occur as the mid-level and surface low wraps around colder air.
  • Far southeastern Kentucky and lower Virginia could get accumulating snow; however, if the surface low jogs slightly south, most precipitation will remain south of the area.
  • I outlined a region in pink, where this storm system could potentially bring unexpected accumulating snowfall. I currently have included the northern metro of Atlanta in this zone. Again, strong forcing will need to offset the very marginal air mass in place. Otherwise, expect a cold rain.
  • I expect only a cold rain across the rest of the Southeast and Mid-South.

Please stayed tuned for subsequent forecasts on this potential winter storm. Don’t forget to download our Southern Snow app. Our app provides you with snow forecasts from both Firsthand Weather AND your local National Weather Service office. Check it out!

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Southeast White Christmas? Part 1

southern snowstorm

We made a post the other day asking our followers when they had experienced their last White Christmas. Quite a few said never. A few others said back in 2010. Since many of our readers live in the Southeast, those responses weren’t all that surprising. Climatologically, having snow on the ground at some point on Christmas Day in the Southeast is exceptionally rare. Though, not impossible. . .

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In the coming days, we’re going to discuss those years that the Southeast had a White Christmas. They may be few and far between, but there’s value in revisiting the conditions and overall pattern that brought those rare snowy Christmases.

In this article, we will take a peek at how the pattern will likely evolve from now through Christmas Day. The overall pattern will remain quite progressive. Meaning, most regions of the U.S. will not remain under the influence of troughing or ridging for more than a few days at a time, if that. Unfortunately, such a setup favors lots of swings in temperatures.

For the first time in a while, temperatures MAY actually feel like Christmas on Christmas Day in the Southeast (give or take a day). Most model guidance agrees that a longwave trough will develop across the eastern half of the U.S., as ridging amplifies across western Canada and eastern Alaska. This pattern configuration favors anomalous warmth along the West Coast and into the Southwest. An anomalously cold air mass will sweep across most locations along and east of the Rockies. Even Florida could get in on this chilly air mass!

Projected departure from average temperatures Christmas Day morning

Most reading this post are already wondering, will there be any precipitation to go along with that brief shot of cold air in the Southeast? Maybe. The models indicate that a shortwave could become detached from the main flow and close off into a mid-level low as it approaches southern California and Baja California sometime next week. It would eventually get swept eastward by the southern stream. But features like these can meander for a while or even retrograde westward before getting reabsorbed back into the main flow. If the cold air intrusion is a strong as modeled, there could be about a two-day window, probably a day or two after Christmas, that any passing southern stream system could produce wintry weather for parts of the Southeast.  

Taking a look at projected 500mb geopotential height anomalies from the latest European model, it already has the longwave trough lifting northeastward by the 26th. At the same time, the closed low quickly moves eastward across Texas/northern Mexico. Residual cold air may hang around for a day or two tops, thanks to a departing surface high. This closed low, or any southern stream feature for that matter, would need to encroach upon the Mid-South and Southeast just as the long-wave trough begins lifting out.

Longwave trough lifts out the day after Christmas

If I were a betting man, I wouldn’t put anything down on a White Christmas happening across the Southeast at this time. Yes, there could be a very brief window for some action right after Christmas Day, but that window appears to be short. I’d certainly recommend not getting too hung up on model guidance in the coming days. Large inconsistencies may exist in how models handle any closed low that develops. But hey, a small chance is always something to watch!

Make sure you download our new mobile app that’s dedicated to providing you with detailed snow forecasts. Firsthand Weather recently launched a new mobile app called Southern Snow for iOS devices, which gives you a snow forecast for anywhere in the U.S! If snow starts showing up in the forecast, Southern Snow will let you know.

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Be sure to join us on the Firsthand Weather this Saturday at 2pm ET to get our official White Christmas forecast for the entire U.S.

Find out if you’ll have a White Christmas 2020 this Saturday on Firsthand Weather

The featured image used in this post is courtesy of Jennifer Kyzer, who captured a great shot of an early season snowstorm in SC in 2014. 

Major, Possibly Historic, Winter Storm On The Way

There are is definitely a lot to discuss with the upcoming Friday/Saturday winter storm that could end up being significant and potentially historic. While it has become certain that there will be a big winter storm, the uncertainty lies in determining the overall storm track and placement of heaviest snowfall accumulations. Given that it’s only Tuesday night, a lot can change on specifics, so it’s important to keep that in mind, especially when reading any forecasts that are based entirely on forecast models. I know I bring this up a lot, but I always want my audience to be aware of the limitations of such an approach. I’ll be discussing the various solutions that are being shown on the latest model guidance, but in addition, I’ll be pointing out specifics that the models may not be handling well with this system. Due to the complex nature of this upcoming system, I may be required to do a follow-up article that includes some changes, if needed.

Discussion (Friday through Weekend System):

A vigorous shortwave (disturbance) will be moving into the Pacific Northwest, and as it moves southeastward, it will dig into the Southern Plains. A surface low will move/develop over the Plains in response to this disturbance and move eastward across the Southeast, as this disturbance treks eastward. This will eventually trigger the development of a long-wave trough in the eastern U.S., and colder air should begin getting wrapped around the low pressure system. This energy will eventually transfer to the coast, and a coastal low should move up the coast.

There is higher than average confidence on how this system will evolve, but the specifics on the exact track are going to be difficult to nail down. The GFS model and most of its ensembles, along with the Canadian model, have the original surface low moving up through Tennessee before its energy gets transferred to the coast. The European model is now showing a more southerly track across the Gulf Coast states, which would allow for some accumulating snow to fall farther to the south and would shift the core of heaviest snowfall farther south, also. On almost all guidance that I have seen, a pretty stout warm nose is initially present well north into eastern Tennessee and even southern regions of Kentucky. This is likely due to the placement of the original surface low and the orientation of the long-wave trough.

To complicate this forecast even further, a cold air damming scenario could set up east of the Appalachians, allowing temperatures to stay below freezing at the surface in places, despite the warm air advection that will likely try to pump northward, overrunning this cold. This sets up a tricky forecast from Northeast Georgia, parts of Upstate South Carolina/extending east and central-east North Carolina (excluding the coast) Even with the system taking a more northerly track, the colder air at the surface may not get out quickly enough before a nasty ice situation unfolds across the mentioned areas.

The latest Canadian represents this possible ice situation well on Friday:

Canadian ice

Snowfall will likely start falling across northern and central Arkansas Thursday night going into Friday and expand into parts of southern Missouri and into the western third of Tennessee. Snow will eventually spread eastward into Kentucky and parts of the lower Ohio Valley through Friday and eventually expand into the Mid-Atlantic states including West Virginia, Virginia, North Carolina, Washington, D.C., and into the Mid-Atlantic states later on Friday going into Saturday. Southern Pennsylvania, including Philadelphia could be hit hard, along with parts of New England, especially along the coast. This is going to be a slow-moving system, and backend snow could fall as far south as the northern third of Mississippi, Alabama, Georgia, much of Tennessee, and into northern parts of South Carolina. Depending on track, there will likely be a region of very heavy snowfall amounts falling, including many of the regions that I just mentioned. This system has the potential to rival or beat some of the historical winter storms of the past and is looking similar to the January 1996 blizzard.

Just To Reiterate A Few Points:

• The European model has been depicting a more southern track. I’m skeptical of this solution currently, although I’m not ruling it out entirely. If there is a southern trend in the track, snowfall accumulations would likely fall farther south and the heaviest snowfall accumulations would shift south. This would also exclude the most northern regions mentioned in this article from getting heavier accumulations.
• A warm nose extending as far north as eastern Tennessee could cause many of these regions to get rain before possibly seeing a transition to some snow (possibly heavy) on the backend of this system. Accumulations would be possible but not as heavy as in surrounding regions.
• Due to cold air damming, an icy situation could setup initially across northeastern parts of Georgia, Upstate SC and possibly extending eastward across the state and into central-eastern portions of North Carolina (excluding the coast). A transition to snow could eventually occur in these regions, with higher accumulations occurring the farther north one goes.
• The core of heaviest snow accumulations could fall somewhere from northern Arkansas/southern Missouri into northwest and north-central Tennessee, across Kentucky, and particularly into the Mid-Atlantic states extending into parts of North Carolina. Many regions in this zone could be measuring snow in feet before all is said and done.

I will continue to monitor this situation closely. I posted a map that shows a 72-hour snowfall output map based on 15 previous winter storms that look similar to this one, courtesy of CIPS Analog Guidance:

snowstorm analog

Just keep in mind that I’m expecting snow to fall west of this region as mentioned in my article, but I did want to show you this map.

Anyway, I will definitely have to make edits to this forecast, since it’s a difficult and tricky forecast. Someone is going to get hit very hard with this winter storm, and at this point, it’s a matter of determining where. More updates to come. . .