I know everyone wants a Final Answer right now about what to expect for this weekend, but sadly, there is no final answer to give. Recall last week, I mentioned that trying to forecast this upcoming event – given all the extra mumbo-jumbo going on – was a lot like trying to forecast where a bike was going to go after ‘ghostie-ing’ it.
That said, model data is starting to come to a better agreement regarding the ‘goal posts’ or the ‘fence’ that temperatures will likely end up falling between. Not perfect, but it is a start.
Up High
One of the factors that is throwing. a wrench in the ability to produce an accurate forecast is the lack of airplanes flying and collecting observations from a ton of airports around the nation and the globe. Those observations are plugged into the model data to help fill in the gaps between places where weather balloons are not launched.
The other factor is the Polar Vortex that has calved off a big chunk of cold and that big chunk of cold is spinning around just north of the Great Lakes. The anomalous cold air ends up playing havoc with the models ability to latch onto plausible outcomes.
Plus – as pointed out by Jeff Frame, the GFS model has a cold bias, which kicks the cold farther south than it actually should as you move further into the future.
NCEP documented a cold bias that gets worse with increasing lead time in the current GFS, but v16 should fix most of it, especially d (bias)/dt > 0.
— Jeff Frame (@VORTEXJeff) February 6, 2021
The cold air, higher up in the atmosphere, will not make it as far south. Only the cold air closer to the surface will ooze into the Southeast.
In fact, looking at the 500mb map from the GEFS, it shows a pretty stout area of cold air up in Canada and the Upper Midwest.
By Saturday night and into Sunday morning, according to the GEFS model data, this pocket of cold air dips about as far south as it will get, right along the border with Minnesota and Canada. That leaves a big chunk of the Great Plains, Midwest, upper Midwest, and Great Lakes underneath a lot of cold air aloft as well as a lot of cold air at the surface.
A big bowl of cold!
Farther south, though, things will be “colder than normal” but not quite as Arctic as the north. Instead, when looking for the colder air to leak farther south, you have to look closer to the surface.
Down Low
During the same time period as highlighted above, Saturday night and into Sunday morning, at 850mb (closer to the surface) cold air looks to make it pretty far south according to the GEFS model.
But notice that the cold air makes it farther south…. in Texas. While the Gulf Coast area is not blue, and even in red. That colder air does eventually shift to the east, but it doesn’t do so until Tuesday.
That means that if any cold air is going to push into the southeast, it will have to do it almost at the surface.
There we go! Temperatures will be running between 20-degrees below average Northern Louisiana & Central Mississippi) to around 5-degrees below average (Mississippi & Alabama coastline) during the same time period.
This is to be expected. Because cold air is dense, It sinks! So most of the cold air will be at the surface.
But those are the anomalies. What doe sthe GEFS think the actual temperature may be at this point?
There is a pretty sharp line in there, where temperatures will be near 50F in Mobile, Alabama and near 32F in Jackson, Mississippi.
By Sunday morning at 7am, though, temperatures across most of the area are down to at of below freezing. Same for Monday morning.
Too Slow
So far it looks like the cold air is moving pretty slowly. Especially aloft. And perhaps too slowly to offer a true threat for much snowy precipitation in the Gulf Coast region. And specifically for south Mississippi.
While, yes, the potential for wintry precip can’t be ruled out. And yes, there is a chance! That chance for snow looks pretty small right now.
Switching over to the ECMWF Ensemble guidance, as they actually offer this information graphically, you can see that the highest peak for any ensemble member was just 0.70″ of snowfall for south Mississippi. And that doesn’t snow up in this model until next Monday night into Tuesday morning.
Looking out a week for snow totals is an exercise in disappointment, as a lot can change in a week.
Even the NBM, looking out a full 10 days, is showing a scant snowfall potential.
Instead, it looks like – if anything – the area will have a better chance for freezing rain or sleet. This is because of that not-as-cold air in the 850mb layer of the atmosphere. That will likely melt any snowflakes, but the colder air at the surface may allow that melted snowflake to re-freeze as it hits the ground.
But it would have to be at or below freezing while precipitating for that to happen.
So will it be cold enough and precipitate at the same time?
That is the million dollar question! And, a lot like I mentioned above, I don’t have a Final Answer. But! I think if you are looking for wintry precip to happen, I can give you a few ‘goal posts’ to aim for.
Timeline for wintry potential
Sunday night – Monday morning: As a little system zips by (mostly to the south, as it appears right now) there may be a brief window for very light sleet or very small flurries of snow to fall. This is supported in both the GFS and ECMWF model guidance. But a lot like back on January 13th, any precip will be very light.
Monday morning: Probably the coldest morning we will see across the region. Temperatures by Monday morning before sunrise will likely be at or below freezing for everyone. Some spots (especially the farther north you go) will be in the 20s. This may be a time when dripping faucets may be necessary for some. Who specifically? We are still trying to nail that down.
Tuesday morning: Depending on how things shake out with the storm track, there may be another brief chance for some sleet on Tuesday morning before things switch over to rain. But this opportunity will be highly dependant on storm track. Farther north? Just rain. Farther south? Sleet-o-rama. Too far south? Nada.
What is the chance that the timeline actually happens and we see wintry weather?
Not great. But not zero. I would lean toward saying the best chance in the region to see a few sleet showers, at some point between Friday and Tuesday, would be if you live near I-20 or north. But beyond that, I can’t say anything with certainty.
The Bottom Line
We know, and we are pretty certain, it will be colder this weekend than it will be during the work week.
At this point, I would treat this like Hurricane Season and there is a Major Hurricane in the Caribbean pointed toward the Gulf. There isn’t any reason to think that it will come here. But given the available evidence and data, there isn’t a compelling argument to say we definitely won’t see something, either
And while, again, I know everyone wants to know the what will happen as soon as possible, in this particular case, things are rather tricky. And it isn’t a simple cut-and-dry situation.
Plan for things to get colder starting Friday and into the weekend. Temperatures will be near- or below-freezing overnight Saturday night into Sunday, Sunday night and into Monday and Monday night and into Tuesday.
Prepare for wintry weather. While it isn’t a guarantee, by any means, it never hurts to be prepared! Have plans to do something outside this weekend? Make a backup plan! Need to travel on Monday or next week? Make sure you keep up on the forecast along your route! Little things now can help you out should anything actually happen.
And keep up with the forecast. Things change. And in this case, things will change more than usual. Don’t get caught off-guard later this week when the forecast changes and something speeds up or slows down, or there is a better chance for precip, or if there is a better chance for more cold.
