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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All Hope Isn’t Lost for Wintry Precipitation Occurring in the Southeast and Southern Plains This Winter

I’m currently keeping a close watch on the small but noteworthy possibility of a winter event occurring across parts of the South after January 15th.

If you strictly look analyze model data at the mid and upper levels of the atmosphere, you’d be tempted to believe that the pattern is complete garbage for wintry weather probabilities farther south. However, the GFS model has a ridge building into the Gulf of Alaska and Alaska and a trough downstream of that ridge just off the West Coast. Then, it has a broad ridge over the central U.S with another trough over New England. Overall, the mean-layer flow is pretty zonal across the central U.S. and Southeast. Ridging usually means warmer weather, but how is this different?

You must consider the placement of these features aloft, and what will occur at the surface in response. I drew some arrows to show the overall flow with a pattern like this. Essentially, winds aloft go up and over the ridge, and winds also go around and under the base of the western trough. As a result, confluence occurs over western Canada. In response, surface high pressure develops over western Canada, and if the high moves into the U.S., it funnels cold, Arctic air into the U.S. due to the clockwise flow associated with high pressure in the Northern Hemisphere.

If a southern stream shortwave were to become embedded within the zonal flow and precipitation were to occur as a result, then it’s not entirely impossible to get some wintry precipitation (ice or snow) across parts of the Southern Plains and Southeast with this type of pattern.

Keep in mind that this pattern needs to keep showing up in the models. Any minor changes in the placement of these mid to upper level features can greatly change the outcome of a forecast. I do believe there’s value in using pattern recognition to consider the different possibilities using model data. Even if nothing occurs, it’s still good to learn about what would happen under a given pattern.

High Impact Winter Storm To Impact South & Southeast

The forecast is still on track for a high-impact winter storm to impact the South and Southeast beginning Monday night and continuing into Tuesday. Rain will transition to snow initially across parts of far northeast Texas, east Arkansas, west Tennessee and north Louisiana by late Monday night. The transition line (from rain changing to snow) will move east and south by early Tuesday morning into central Tennessee and Mississippi (see Fig. 1) before moving east into parts of Alabama and Georgia later on Tuesday (see Fig. 2). Parts of upstate South Carolina and North Carolina should get in on the rain & snow later in the day on Tuesday.

Fig. 1: Future radar early Tuesday morning
Fig. 2: Future radar Tuesday afternoon

It should be noted that this may map need to be tweaked over the next 24 hours. Locations further west on this map (east Texas and western Louisiana) may see lesser totals that what is indicated on this map. It depends on how quickly the rain transitions to snow and also how much moisture is available in this region. Most areas within the 2-4″ zone will see 2-3″ of snow with scattered 4″ amounts. Some of the higher terrain with this 2-4″ zone will see amounts closer to 6″.

Fig. 3: Snowfall accumulation forecast

It is likely that travel will become difficult across parts of the South and Southeast on Tuesday. This thought has allowed local National Weather Service offices to issue Winter Storm Watches and Winter Storm Advisories for a large part of the region (see Fig. 4). One issue that may make roads extremely dangerous is the potential for the initial rain to freeze on roads once surface temperatures drop. This glaze of ice would then be covered by snow; making road conditions extremely hazardous.

Fig. 4: Latest winter weather products

Please keep checking back for updates. An additional article will be published later this evening for locations further north.

Updated Snowfall Forecast

We continue to monitor the chance for snow across much of the South and Southeast from Monday night into Tuesday. Most of this region will see the opportunity for snow accumulations that could impact travel. The worst travel conditions appear to be on Tuesday from northern Louisiana eastward into northern Georgia.

The first areas to experience snow will be far eastern Oklahoma, northeast Texas, Arkansas, western Tennessee and northern Louisiana by late Monday night. The rain & snow will move east and southward by early Tuesday morning into central Tennessee and parts of Mississippi (see Fig. 1) before moving further east into parts of Alabama and Georgia later on Tuesday (see Fig. 2). Parts of upstate South Carolina and North Carolina should get in on the rain & snow later in the day on Tuesday (see Fig. 3).

Fig. 1: Future radar late Monday night (please note: this should be used as an estimate–exact placement of precipitation may change)
Fig. 2: Future radar early Tuesday morning (please note: this should be used as an estimate–exact placement of precipitation may change)
Fig. 3: Future radar Tuesday afternoon (please note: this should be used as an estimate–exact placement of precipitation may change)

Accumulations do look likely from late Monday though Tuesday. The event being a few days out makes it extremely difficult to forecast snow accumulations, however. There are two negative factors for accumulations. I) Monday (the day before the snow) will be warm across this region, which will lead to warmer ground temperatures, and II) the window for snow is only about a 4-6 hour period. Even with these two mitigating factors, this event will be the best chance so far this season for accumulating snow across the South and Southeast.

The snow rates should exceed melting and the best chance for accumulations will across northern & central Mississippi, Tennessee, northern & central Alabama, northern Louisiana and northern Georgia. Guidance is evening indicating some instability, which could lead to convective banding of snow (this is where the heaviest snow totals are possible). It is too difficult to pinpoint where those bands may setup. That is almost a nowcasting scenario. Secondly, areas that see snow pre-dawn on Tuesday will have the best chance to see accumulations and nasty road conditions. Even though it is difficult to forecast snow accumulations this far out, I wanted to provide you with a second preliminary snow accumulations map (see Fig. 4). Please note, this will likely change over the next 48-72 hours as we get closer to the event. It is possible the polygons may need to me reduced or expanded, and snow totals may need to be increased or decreased.

Fig. 4: Preliminary snow accumulation map

The South and Southeast are not the only regions that have snow in the forecast. Coastal areas of North Carolina and Virginia may see snow beginning Monday due to a coastal low that will quickly deepen off the coast. This could allow a band of snow to setup from Virginia Beach down into eastern North Carolina. If this happens, it is possible heavy accumulations may occur, which is why this small area is included in the 2-5″ zone. It should be noted, most numerical guidance indicates the low will be too far off shore to aid in precipitation chances for this area, but we believe the low may closer to the coast, thus, have reflected this in the snow accumulation forecast. Regardless, snow chances increase for this area by Tuesday night into Wednesday. Those snow chances also increase for the rest of the Mid-Atlantic and the Northeast by Wednesday. Parts of the Northeast, Great Lakes and Ohio Valley will see multiple snow opportunities from Sunday through Wednesday so accumulations are likely (see Fig. 5). More than one foot of snow is possible for parts of the Great Lakes region where lake effect snow band establish themselves.

Fig. 4: Preliminary snow accumulation map

Please keep checking back for updates as this is a fluid forecast and changes may be needed!

Accumulating Snow Likely For South And Southeast!

The chance for snow continues to increase for parts of the South and Southeast early next week. An arctic cold front will move out of the Southern Plains into the South by Monday afternoon with temperatures quickly falling to near or below freezing behind the front. At the same time, an upper-level shortwave will move overhead. This shortwave combined with the vertical profile of the cold front will generate a strong upward motion in the atmosphere to allow precipitation to develop along and behind the cold front. Precipitation immediately behind the front will fall as rain Monday night and quickly transition to wet snow by Tuesday.

The first areas to experience snow will be far eastern Oklahoma, northeast Texas, Arkansas, western Tennessee and northern Louisiana by late Monday night. The rain & snow will move east and southward by early Tuesday morning into central Tennessee and parts of Mississippi (see Fig. 1) before moving further east into parts of Alabama and Georgia later on Tuesday (see Fig. 2). Parts of upstate South Carolina and North Carolina should get in on the rain & snow later in the day on Tuesday.

Fig. 1: Future radar Tuesday morning (please note: this should be used as an estimate–exact placement of precipitation will change)
Fig. 2: Future radar Tuesday afternoon (please note: this should be used as an estimate–exact placement of precipitation will change)

While this is not a setup that climatologically produces major snow events, it increasing in likelihood that accumulations are likely. The event being a few days out makes it extremely difficult to forecast snow accumulations. There are two big negative factors for accumulations. I) Monday (the day before the snow) will be warm across this region, which will lead to warmer ground temperatures, and II) the window for snow is only about a 4-6 hour period. With that said, this does appear to be the best chance so far this season for accumulating snow across the South and Southeast. The snow rates should exceed melting and the best chance for accumulations will across northern & central Mississippi, Tennessee, northern & central Alabama, northern Louisiana and northern Georgia. Guidance is evening indicating some instability, which could lead to convective banding of snow. This could dump heavy snow amounts for isolated locations. It is too difficult to pinpoint where those bands may setup. That is almost a nowcasting scenario. Secondly, areas that see snow pre-dawn on Tuesday will have the best chance to see accumulations and nasty road conditions. Even though it is difficult to forecast snow accumulations this far out, I wanted to provide you with a preliminary snow accumulations map (see Fig. 3). Please note, this will likely change over the next 48-72 hours as we get closer to the event. It is possible the polygons may need to me reduced or expanded, and snow totals may need to be increased or decreased.

Fig. 3: Preliminary snow accumulation map

Please keep checking back for the latest updates!

Southern Snow Next Week! Accumulations Likely

The chance for snow continues to increase for parts of the South and Southeast for early next week. A potent cold front will move out of the Southern Plains into the South by Monday afternoon. Temperatures behind this front will quickly fall to near or below freezing. At the same time, an upper-level shortwave will move overhead. This shortwave combined with the vertical profile of the cold front will generate a strong upward motion in the atmosphere to allow precipitation to develop along and behind the cold front. Precipitation immediately behind the cold front will fall as rain Monday night and quickly transition to wet snow by Tuesday.

The first areas to experience snow will be eastern Oklahoma, northeast Texas, Arkansas, western Tennessee and northern Louisiana Monday night. The rain & snow will move east and southward by early Tuesday morning into central Tennessee and parts of Mississippi (see Fig. 1) before moving further east into parts of Alabama and Georgia later on Tuesday (see Fig. 2). It is possible parts of upstate South Carolina may even see a light rain & snow mix by late Tuesday.

Fig. 1: Future radar Tuesday morning (please note: this should be used as an estimate–exact placement of precipitation will change)
Fig. 2: Future radar Tuesday afternoon (please note: this should be used as an estimate–exact placement of precipitation will change)

While this is not a setup that climatologically produces major snow events, it appears accumulations are possible if not likely. Being a few days out, it is extremely difficult to forecast snowfall amounts. Especially given the warm day before the snow falls. However, the snow rates should exceed melting and the best chance for accumulations will across northern & central Mississippi, Tennessee, northern & central Alabama, northern Louisiana and northern Georgia (see Fig. 3). At this point, it appears some areas may see 1-4″. This will impact travel, especially for areas that see snow fall pre-dawn on Tuesday.

Fig. 3: Preliminary snow outlook

It should also be noted, a weak shortwave will move into the South and Southeast late Saturday into Sunday. Overall, this shortwave should not develop much precipitation but a sprinkle or flurry is possible across northern Mississippi, northern Alabama and northern Georgia during this timeframe. Again, do not expect anything significant. It is likely that most areas will only see an increase in clouds. Late next week also needs to be monitored closely as a strong arctic front moves into the South and Southeast. A strong temperature gradient could allow for a surface low-pressure to develop, which could generate wintry precipitation for the region (more details to come as we get closer).

Monitoring Winter Weather Potential For Southeast

We are keeping an eye on the upcoming work week for the Southeast for the potential of wintry weather. The first chance for wintry precipitation begins Tuesday night into early Wednesday for parts of the Carolinas and northeast Georgia. A weak ridge will build eastward (as a trough moves into the Plains), allowing moisture to stream into the region late-Tuesday. At this time, the Arctic air currently in place, will have begun to modify, but surface temperatures will still remain cold. As the moisture begins to move into this region, it is possible drizzle or light rain will develop Tuesday night. The low-level temperatures *could be cold enough for light freezing rain to fall Tuesday night into early Wednesday. Forecast soundings for this timeframe show wet-bulbing will occur possibly allowing for light freezing rain in the highlighted areas (see Fig. 1). As moisture continues to move into the region, temperatures will rise above freezing by late-Wednesday morning. This will minimize accumulations and allow the freezing rain to transition to all rain.

Fig. 1: Areas that have the best chance to see freezing rain

The next opportunity for wintry precipitation arrives late Wednesday into Thursday. The aforementioned trough will continue eastward, sending a cold front into the Southeast. Numerical guidance has trended towards the trough becoming neutrally tilted as it moves east of the Mississippi Delta, which would allow surface temperatures to fall rapidly behind the front. It is possible lingering moisture will be present behind the cold front, which could allow a 2-4 hour window for rain to mix with or change to light snow (see Fig. 2). At this time, it does not appear significant accumulations are likely. We will have to keep a close eye on this event as we get closer to Wednesday night and Thursday. A slower departure of moisture could allow for more meaningful snowfall to occur.

Fig. 2: Areas that have the best chance to see rain/snow

Another upper-level feature could aid in wintry precipitation as we head into the weekend for the Southeast but this is too far out and confidence is low. Keep checking back for updates.

What’s All Of This Talk About A Southern Winter Storm Next Weekend?

Is it really that time of year again already? For most of us, we skipped fall and went straight into winter last month. Although wintry precipitation has already impacted parts of the United States, the first legitimate chance for a winter event farther to the south will come in about 6 or 7 days. The goal is never to address local-scale specifics in the long-range, but we can begin discussing the pattern that could support a winter storm. This allows us to establish an initial framework by looking at the big picture first, and then we can build upon that foundation with specific details in the coming days.

Will the mid and upper-level atmosphere support an early-season winter storm across portions of the South?

The first step, especially at this point, is to look at what’s currently going on well-above the surface and attempt to determine how that pattern will evolve over time. From this, it’s possible to infer what could occur at the surface without it being necessary to look at modeled surface output at this point. A closed mid-to-upper level low pressure system was located over the central U.S. yesterday (Saturday) and has now moved northeastward over the Great Lakes. A cold front, associated with a surface low that developed in response, will push all the way through Florida by mid-week. Broad troughing will remain established over the eastern U.S., keeping an anomalously cold air mass in place.

Now, here’s the main reason I made a post on November 29th about the possibility of a winter storm. A split-flow regime is expected to become established over the far western U.S. Let me explain what that means. With this setup, the jet stream splits into northern and southern components. The northern component (the polar jet) will extend well into western Canada and Alaska, while the southern component (the southern jet) will eventually dip into Baja California. Now, check out the map I posted under this paragraph. You can see the broad trough over the eastern U.S., ridging over western Canada and Alaska, and a shortwave extending into southern California and Baja California. I drew arrows to indicate mid and upper-level flow. Do you see how the flow begins to merge back together over the central U.S.? When this occurs, this is called confluence. As this confluence occurs, this will result in sinking motion over the Great Plains and will support the development/maintenance of strong high pressure over that area. Winds flow clockwise around a high pressure system in the Northern Hemisphere, and cold, Canadian air, will wrap around on the east side of this high. There’s your cold air source.

GFS 500 mb map

This will allow another cold front to push southward, and a surface low will develop in response to favorable dynamics just to the east of the shortwave over California. As this shortwave treks eastward late week into early weekend, so will the surface low, which will probably ride somewhere along the frontal boundary. This will result in rainfall across drought-stricken southern California and the Southwest and a swath of wintry precipitation that will extend somewhere from the Southwest/Southern Plains to the East Coast.

If you were to ask me how far to the south I believe frozen precipitation will occur, in short, I’ll tell you I don’t know. But, I’ll give you some insight on this. With conditions favoring high pressure over the central U.S., I’m comfortable saying that it wouldn’t be too difficult to get frozen precipitation (snow and/or ice) as far south as parts of Oklahoma, Arkansas, and Texas. Farther eastward into Tennessee and northern Mississippi/Alabama/Georgia, it becomes a bit more of a tough call. I’m especially paying close attention to northern South Carolina, most of North Carolina, and parts of Virginia, due to the potential for cold air damming to establish itself east of the Appalachians as surface high pressure moves eastward. That’s why in our ‘best chance for wintry precipitation’ map (shown below), we currently depict higher probabilities across those locations. Of course, it should go without saying that we will have to modify this map between now and next weekend, and keep in mind that wintry precipitation is not exclusively snow. We can iron out all of those details later.

southern snow/ice forecast

Conclusion:

Again, we’re simply trying to determine how this pattern will evolve. Any unforeseen changes in that would completely throw off my current expectations for next weekend. Have fun looking at all of the snowfall projection maps, but it’s important to understand the major limitations of accumulation projections this early in the game. And no, I’m not expecting nearly 3 feet of snow in parts of South Carolina like what the European model is showing.

european model snow forecast

Be sure to follow us on Facebook for numerous updates on this event throughout this week. Also, please give us a follow on Instagram. We’re really trying to grow that account. As always, continue to check back with us daily for new updates.

A special thank you to Kimberly Gnat for sharing a picture with us of the snowstorm near Chicago late last month, which we used as the featured photo.

Winter Storm Inga To Impact A Large Swath Of The United States

As an upper-level low pressure system digs southeastward towards the Great Lakes, a potent shortwave is going to continue digging southeastward across the Great Plains and Mississippi Valley tonight. An associated surface low is currently located in the Great Lakes region, and an Arctic cold front will continue sweeping southeastward. The positive-tilt (southwest to northeast orientation) of the trough has resulted in westerly/southwesterly flow across a deep layer of the atmosphere extending from the Southern Plains to the Mississippi Valley/Mid-south, Southeast, Tennessee/Ohio Valley, Mid-Atlantic, and Northeast. Despite a shortwave feature this past weekend ushering in colder and much drier air, the current pattern configuration has allowed/is allowing for some moistening of the atmosphere across most regions ahead of the Arctic front. Across most regions that are expecting to get snowfall tonight into tomorrow, this should allow for snow to begin reaching the ground sooner, although a decent amount of evaporation will still occur initially.

The unusual aspect of this setup, especially for southern locations that will be getting snow and/or ice, is the fact that there will be no generation of a surface low that will trek from southwest to northeast across the South. This is a scenario where enough lift will be generated along the Arctic front that snow will be able to fall at a decent clip, which is already occurring along a zone from southern Missouri/northern Arkansas to the Ohio Valley/Great Lakes region. That southwest to northeastward band of snow will continue moving/developing southeastward as favorable dynamics/lift sets up across additional regions (map included below). This upward motion will be further enhanced by a jet streak (a region of fast-moving air) that will be located to the right of the trough axis. When more air in the upper-levels of the atmosphere leaves than what is coming in, the atmosphere tries to compensate for that; thus, air begins to rise across that region. If there is enough moisture across that zone, it begins to condense and can produce precipitation.

The big concern with the air mass behind the front is how severely cold it is. As the drier and much colder air mass begins to intrude southeastward, any snowfall that initially melts on the roadways due to warmer temperatures today will result in major travel issues. Snow ratios will increase as the colder air seeps southward, so it will take less moisture to cause hazardous conditions. I’ve noticed that some meteorologists are drawing some comparisons to the event that unfolded in Birmingham and Atlanta in 2014, which resulted in people being stranded along roadways for hours, and honestly, it is a fair comparison.

winter storm inga snowfall map

We made some tweaks to our forecast since this morning. We upped the totals in our heaviest (purple) accumulation zones. Using a 10:1 snow to liquid equivalent ratio that is often shown on forecast model pages will not suffice with this setup; thus, this is why these totals are a bit higher than what you might be seeing on the model guidance. After much discussion, we went ahead and widened the 1-2 inch and 2-4 inch zones across the Carolinas and parts of eastern Georgia and included a zone of accumulations in southeastern Alabama and southwestern Georgia. We also specified ice accumulations across the zones that we foresee getting ice. Out of an over-abundance of caution, I suggest residents in regions, such as Atlanta, prepare for this event accordingly, despite our actual accumulations being on the low-side. Given that temperatures will rapidly drop behind the Arctic front, just a dusting to light accumulations could result in extremely hazardous traveling conditions. While a dusting/light accumulations may not be a concern in most cases, it actually will be in this scenario if they do occur.

Please be on our Facebook page tonight at 9:30 pm ET (8:30 pm CT) for a live Facebook discussion with Chris. You will be able to ask him any questions that you might have. In the meantime, we will continue to monitor this situation and will mention any necessary tweaks to the forecast in that video.

Early-Season Winter Event Looking More Likely For Parts Of The Southeast

It’s only December 6th and we’re already talking about the potential for a winter event across parts of the Southern Plains and the Southeast. Since we’ve already covered the forecast for the Southern Plains, I’m going to focus primarily on the Southeast. A system earlier in the week moved across the Northern Plains and has now trekked northeastward into Canada. A cold front associated with that system pushed across the eastern U.S. earlier in the week and has now made its way to the Gulf coast and along the East coast. Behind the front, a broad trough has become established over the eastern two-thirds of the nation. With this kind of setup, mid to upper-level wind flow across the southeastern U.S. is generally from the southwest; thus, the initial cold front has already slowing down and will eventually stall out near the Gulf coast and East Coast. The shortwave feature that will be responsible for bringing snow to Texas is going to interact with the broad trough and a second shortwave feature. This interaction is going to sharpen the trough, which will eventually extend into the Southeast. Given that the frontal boundary will be stalled out near the coast as all of this is unfolding, this is going to induce the development of a surface low pressure system that will ride along that boundary along the Gulf coast and up the East coast.

For those in the Southeast, most who have lived in that region for any extended period of time know that most winter storms that unfold across that region involve a low pressure system developing near the coast along the Gulf of Mexico, which then crosses over and moves off or along the East coast. Since cold air is often limited, forecasting these events can be challenging throughout the extent of the event. Since it’s still early December, that even adds additional challenges.

First and foremost, it should be noted that most of the model guidance suggests at least some wintry weather (snow!!) across the Southeast (more on specific locations in a bit). However, snowfall accumulation projections range from no accumulations to several inches of snow for parts of the Gulf coast northeastward to the East coast. For events such as these, I either like to see that a pre-existing colder air mass has become established over the region before the event, or that there is going to be sufficiently cold air provided by a certain atmospheric feature in time for the event (for example, high pressure over the Northeast). The first cold front that has now pushed through the region has brought in much colder conditions, but given the broadness of the trough and the time of the year, there really needs to be an additional source of colder air spilling into the region. Throughout the day on Thursday, the colder air to the north-northwest of the area will continue pushing southeastward, but despite that, we’re still going to be dealing with the classic borderline winter storm/event in the South.

The NAM model has generally been the most aggressive with snowfall accumulations across the Southeast, which extend those accumulations down the Gulf coast. The hefty snowfall accumulations occur for most locations later on Friday into Friday night, even though it has precipitation (mostly rain) spreading across many locations in the Southeast tomorrow. If you’re looking to get noteworthy accumulating snow, it’s best this event occur later on Friday like what the NAM is showing for many locations, and given that it would be getting dark or already dark, this would greatly increase the odds that temperatures would be sufficiently cold throughout the atmosphere to support snow or a transition from rain to wet snow. This would also allow more time for colder air to seep southeastward. The GFS is less aggressive, primarily because it has the heaviest precipitation moving out more quickly. The European model, which is generally more reliable, falls somewhere in between with accumulations. Remarkably, all of the guidance is at least showing some accumulating snowfall for some locations in the Southeast. However, it should be noted that these maps depict a 10:1 snow to liquid ratio, but given the warmer ground temperatures and the fact that rain will mix in (at least initially), these totals could be overestimated for some locations on all three models. However, higher snowfall rates across some locations could offset some of these hindrances for snowfall accumulations.

NAM model snowfall map

Figure 1: NAM model snowfall accumulation forecast for the next 72 hours. Source: Tropical Tidbits

GFS model snowfall map

Figure 2: GFS model snowfall accumulation forecast for the next 72 hours. Source: Tropical Tidbits

European model snowfall map

Figure 3: European model snowfall accumulation forecast for the next 90 hours. Source: Ryan Maue

Remarkably, residents living in southeast Louisiana, southern Mississippi and possibly extending into western parts of Alabama have the greatest chance of this event unfolding for them. Since this region will be some of the first locations to feel the effects of the colder air mass digging southeastward, precipitation developing and moving across the region will have the greatest chance of making the transition to snow either late Thursday or early Friday. Predicting snowfall accumulations from eastern parts of Alabama into Georgia and South Carolina gets quite challenging. The later this event unfolds for those locations on Friday, the better for accumulating snowfall. The more aggressive snowfall totals that span across parts of North Carolina into southeastern Virginia are warranted. That’s another region that I feel has a pretty decent chance of this event unfolding.

Due to the uncertainty that exists, this will require me to post a follow-up update tomorrow. However, residents in the general swath of accumulations that are being depicted by the model guidance should prepare for this event. I expect the majority of accumulations to occur over grassy surfaces; however, issues on the roadways could occur for localized regions where the snowfall rates are higher. That will be something that we’ll have to determine tomorrow. Nonetheless, it is still very early in the meteorological winter, and it’s remarkable that we even have an event such as this to forecast! Firsthand Weather will keep everyone updated as much as possible before and during this event and will be posting numerous updates on our Facebook page.