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UPDATE: Snow chances for Friday into Weekend

UPDATE — 1/4/17 @ 6:38am CST:

Following up on our weather discussion from yesterday in regards to winter weather that may impact the Sequatchie Valley later this week and into the weekend. There is still great uncertainty regarding the evolution of winter weather or even a winter storm, but I’ll discuss what we know and try to explain the pattern leading up to this potential event.

Forecast guidance is struggling with consistency in regards to the placement of synoptic features leading to a potential wintry shot for low-latitudes. The thinking as of this morning, a trough will dig into western Texas late in the week. As the trough digs further into Texas, a surface low will develop along the north-central/northeast Gulf Coast. This will setup precipitation chances for parts of the Southern Plains and Southeast. A cold air mass will be oozing into the area at the same time, which will setup an area of snow, and likely an area of snow/sleet mixture across parts of Central and North Alabama as well as the Tennessee Valley and into Southern Tennessee including the southern end of the Cumberland Plateau and Marion County.

It’s too early to determine how much snow will fall due to many unforeseen variables that will come into play. The evolution of the low (if it develops), the track, the position and depth of the cold airmass, and moisture are all critical in determining which areas will see snow, which areas will see a snow/sleet mixture, and how much may fall. It does appear some light accumulations will occur across the South and Southeast, however.

This particular event has proven to be quite a challenge with much “model madness” as the various computer models used for forecasting have shifted back-and-forth several times on snow or no snow and amounts. As we said in our previous update…winter weather events are very complicated to forecast and often can and do change at the last minute, so please be aware that this is just a preliminary weather discussion and not a forecast — all based on several computer models that are relied on by meteorologists across the nation for predicting precipitation and other weather events over a certain time period.

Our team of degreed meteorologists are watching all weather models very closely and updating with any new information as they feel necessary. We’ll continue to stay on top of the weather situation and bring you the latest here at MarionCountyMessenger.com!

 

PREVIOUS STORY:

Just days into 2017 and not even a month into the winter season and our team of degreed Meteorologists are watching the forecast closely over the next few days as the potential chance for a winter weather event looms on the horizon for the Sequatchie Valley heading into the weekend.

To start with, winter weather events are very complicated to forecast and often can and do change at the last minute, so please be aware that this is just a preliminary weather discussion and not a forecast — all based on several computer models that are relied on by meteorologists across the nation for predicting precipitation and other weather events over a certain time period… Again, these are just models and the actual forecast will likely change in one way or another — possibly several times before we reach the weekend.

As it stands the GFS, the Para GFS, Canadian model, the DGEX, and most recently the European model, are on board for a southern winter storm late this week and into the weekend.

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While much uncertainty still exists on specifics, confidence continues to increase that a winter storm (potentially significant) will be impacting the Southeast, among other regions, this weekend.

Currently, a low pressure system is located over the lower Mississippi Valley, which will trek northeastward tomorrow across the Tennessee Valley and Ohio Valley. While this will act to transport warm, moist air into the southeastern U.S. initially, cooler air will rush in behind the low as it moves into Canada.

A series of shortwave troughs, one particularly robust mid-week, will move across the Great Lakes and Ohio Valley and eventually eastward into the Northeast maintaining the general placement of a longwave trough over the eastern part of the country, and a strong cold front will eventually sweep all the way through the Southeast and Gulf Coast states to the East Coast by Wednesday into Thursday.

On Friday, the latest GFS has a longwave trough over the eastern third of the U.S. with a potential winter storm located over the Rockies.

In regards to having the necessary cold air in place for a winter storm across the Southeast, this would ensure it’seems there with the cold air will be in place before the system of interest moves across the Southeast.

While some regions could start with mixed precipitation or even just rain, this is shaping up to be an all-snow event for many locations with a rain/snow line setting up somewhere along the Gulf Coast states.

As mentioned, uncertainties do exist in regards to how far north the precipitation will reach or whether the moisture gets suppressed due to the cold air mass already being in place over the area.  Another factor is deep convection (thunderstorms) along the Gulf coast and Florida that could steal moisture from areas to their north. Again, it’s complicated to pinpoint in advance especially with changing models also showing a degree of uncertainty.

At last check the operational GFS model has a large winter storm for a good portion of the Southeast while the operational European model has generally kept precipitation amounts lighter farther to the north. Regardless, almost all model guidance has some amount of moisture making it fairly far north; however, this puts locations like the Sequatchie and Tennessee Valley and areas north of us into a bit of a “wildcard” for weather.

At this time, the focus is currently on the overall pattern and other “pieces of the puzzle” that will be responsible for this potential event. Models are just models and aren’t always reliable, but act as great aids in helping us better forecast longterm conditions and potential events such as this.

We want to remind you that forecasts, such as those produced by weather apps that are solely based on model data tend to often be inaccurate and often give their users the wrong information due to the way they create a forecast.

Over the next two to three days, we will be able to better see how, when and what areas will be affected and we will update our readers accordingly with the most accurate timelines and what type(s) and amounts of precipitation to expect for our area.

As always, stay with MarionCountyMessenger.com for the latest!

 

 

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