There are two models on opposite ends of the spectrum.
- The NAM4 model thinks it’ll be raining by 10 AM.
Our NWS believes this is too wet, and we agree.
- The second model is the GFS. It has very little/no rain in the morning.
Our NWS believes this is a little too dry.
Considering both models, our NWS is going with 20% to 30% chance of rain in the morning. That’s to account for the possibility the NAM4 is correct.
But, we think we will stay dry. In addition to what our NWS thinks, there’s the High Resolution Rapid Refresh (HRRR) model, which, through 9 AM, still doesn’t have that warm front shoving rain into Tennessee:
So, we think will be good in the morning, but know you’re taking a small risk if you’re planning outdoor AM festivities.
So When’s It Going to Rain?
Again, this depends on the model you prefer. The NAM4 has rain ongoing early afternoon, but the big global models (GFS, Euro) do not.
It looks like an off/on rain event in the afternoon, mostly “off” rather than “on.” Rain chances increase the later in the day you go.
We will be waiting for the arrival of a cold front, swinging in from the west. Rain and storms should form out ahead of it, but that may not show up until late:
The GFS model swings this line in at the exact same time. It’s rare these two models agree on this. Even the Euro is on board with this timing, although it puts “the line” further NW of us.
So, really, we may not see all that much rain before dark Sunday night.
Will There Be Strong Storms?
If it happens, it’ll have to be in the afternoon, before sundown.
This morning, the Storm Prediction Center outlooked us for a low-end severe weather threat. At lunchtime, they backed off that, reduced the threat here, and shifted the higher risk of storms to our NW. Currently, we are in a “Marginal” category — a “1” on a scale of 0 (yawn) to 5 (the end is nigh).
Several things must come together at the same time to get severe weather. Two main severe weather ingredients — shear and instability — are expected to arrive tomorrow, but at different times. Although this “event” may turn out to be a dud the way Thursday’s event did, it won’t be a dud for the same reason. We lacked CAPE Thursday, but all models tomorrow think we’ll have plenty of that. The key tomorrow will be timing – lining up all the ingredients at the same time.
Further reducing our storm concern is that wind shear at the lowest levels will be weak, and the “forcing” (the thing that kicks it all off = the cold front) also looks weak.
All that to say this: we are unimpressed by this severe weather setup. However, it’ll have to be closely watched. If shear and instability synchronize before sundown, we may see damaging winds and maybe some hail. Do not ignore the weather tomorrow.
- We have good reason to think we’ll be dry in the morning, but confidence on that is not great.
- Off and on showers and storms possible in the afternoon. These have a conditional, small, but real, severe potential.
- The severe threat diminishes after sunset, but we should see some rain as the cold front pushes through after dark.
We will be live-tweeting this event all day Sunday at @NashSevereWx.
Rest of the Week
Periods of showers and thunderstorms are expected Wednesday night through Friday, with as much as 2″ falling. We hope to dry out in time for the weekend.
This website supplements @NashSevereWx on Twitter, which you can find here.
Categories: Forecast Blogs