Handy “Will it snow” guide for the South

Seeing that snow is starting to show up within some of the model guidance, I figure I can break out my guide again for everyone.

I came up with a guide for everyone in the South to use to figure out if the model data supports seeing any snow flying around in the air. Perhaps a model map shows “blue” in your area… But that isn’t always the whole story. Sometimes it can snow in the “green” area. Other times it will rain in the “blue” area.

This can’t help you figure out if snow will “stick” or “accumulate” but it can help you figure out if you will see visible snow in the air.

Now, in order to use this guide you’ll need to be able to look at some model data. You’ll need access to a Skew-T and a few model maps like the 700mb Vertical Velocity map.

Using the guide for three areas

Using the above guide, we can quickly look at some Skew-Ts and figure out if the raw data support the chance for any wintry precipitation. This goes beyond just looking at the precip maps and does a better job at identifying the potentials.

South Mississippi

Let’s take a look at the model data from the 12z data on 1/4/20 from the GFS model

Step 1:
Moisture? Yes! Some!
Step 2:
Forcing? Barely. But it counts!
Omega? Not within the Dendritic Growth Zone.
Step 3:
Dry Air? Not much, but it certainly isn’t “moist” either. I think “Sorta” would be best here.
Step 4:
Warm Air layer? Nope! But it is above 32F at the surface
Step 5:
Precipitating? Light wintry mix or rain.

Northern Louisiana

Now, let’s take a look at northern Louisiana for the same time.

Step 1:
Moisture? Yes! Lots!
Step 2:
Forcing? Some.
Omega? Yes. And within the Dendritic Growth Zone.
Step 3:
Dry Air? None.
Step 4:
Warm Air layer? Nope! At or below 32F all the way down
Step 5:
Precipitating? Snow!

Central Alabama

Now, let’s look at the same data for Central Alabama

Step 1:
Moisture? Some in the DGZ
Step 2:
Forcing? Some.
Omega? Some. And within the Dendritic Growth Zone.
Step 3:
Dry Air? None.
Step 4:
Warm Air layer? Nope! At or below 32F almost all the way to the surface, but above 32F at ground level.
Step 5:
Precipitating? Rain/Snow mix

Bottom Line: What does this mean for next week?

Generally, right now, the model data is supportive for the potential for wintry precipitation somewhere across Louisiana, Arkansas, Mississippi and Alabama.

What does this mean specifically? For you? Almost nothing. The model data is going to change between now and then. Perhaps drastically. On top of that, the very tiny details that sometimes go into the difference between snow and no snow can’t be resolved by weather models this far out.

Look at the difference between the models right now:

So this data offers almost zero utility when trying to decipher the specifics of the forecast. Questions like, “Will it snow?” or “How much snow might we see?” are unanswerable with any accuracy. And the data will mean zilch when it comes to specifics until about Thursday.

For now, we are stuck with “Models are showing increased (or decreased) confidence in the potential for snow” or “Data are trending warmer (cooler) and drier (wetter)” as useable information to pass along.

And so far, generally, the data suggest the potential is there. But that is about all we know. The storm system responsible for producing this weather is still off the coast of Japan. It is more than 6,500 miles away.

A lot can change between now and then. In fact, there is still a chance that this storm system may completely miss the area!

So hang tight and we will continue to offer updates as soon as we have any new information.