Friday, May 24, 2024

Watching Sunday Night/Monday Morning for Severe Thunderstorm Potential, Next Week Looks Nice After Holiday

Saturday (High 85, Low 66): Partly cloudy. Scattered showers and thunderstorms are possible. 

Sunday (High 89, Low 68): Mostly sunny, muggy and breezy during the day. Thunderstorms are likely at night, and some may become severe. 

Memorial Day (High 84, Low 70): Scattered showers and thunderstorms are still possible. Rain and clouds slowly diminishing throughout the day and night. 

Tuesday (High 82, Low 61): Mostly sunny. 

Wednesday (High 78, Low 56): Sunny. 

Thursday (High 81, Low 58): Sunny. 

Friday (High 84, Low 60): Sunny. 

Sábado (Máxima 85, Mínima 66): Parcialmente nublado. Es posible que se produzcan lluvias y tormentas aisladas. 

Domingo (Máxima 89, Mínima 68): Mayormente soleado, bochornoso y ventoso durante el día. Es probable que haya tormentas eléctricas durante la noche y algunas pueden volverse severas. 

Día de los Caídos (Máxima 84, Mínima 70): Todavía es posible que haya lluvias y tormentas eléctricas dispersas. Lluvias y nubes disminuirán lentamente a lo largo del día y la noche. 

Martes (Máxima 82, Mínima 61): Mayormente soleado. 

Miércoles (Máxima 78, Mínima 56): Soleado. 

Jueves (Máxima 81, Mínima 58): Soleado. 

Viernes (Máxima 84, Mínima 60): Soleado.

At 12:34 PM, latest observations show some rain and a thunderstorm in the vicinity in Cullman. The temperature is 72 degrees. The dewpoint is 70, and the relative humidity is 94%. Winds are from the Northwest sustained at 8 miles per hour, with higher gusts up to 14 mph. And the visibility is currently down to 8 miles because of the rain. 

The Low this morning was 66, and I forecast 70. So this time the computer models got it right, or closer to being right. 

And these showers and thunderstorms moving through the region this morning are more of the typical kind like you'd get in the summer months, which we're almost into. That one just North of Gadsden is looking fairly strong, could produce wind gusts up to 40-50 mph and maybe some small hail, about pea-sized. But that is below severe criteria. They have a special weather statement out on it, the National Weather Service in Birmingham does, but no warning. They don't issue warnings for lightning or just heavy storms that are not all that dangerous, because as one SKYWARN instructor put it to us, "We'd run you crazy if we did."

So we are mostly under the influence of high pressure centered up in the Virginias, but the cold front is across the Midwest, Ohio Valley, and the Plains today. It won't pass through our region until Monday, which is Memorial Day. In the meantime we are in this unsettled pattern. And kind of like in summer, there can be mesoscale boundaries that cause showers and thunderstorms to fire up from day to day. Some people like to analyze those local boundaries a lot, but I don't bother usually. These kinds of showers and storms strike me as random. 

We do have a severe thunderstorm near Amory and East Aberdeen in Mississippi. And some flash flood warnings affecting places like Union City and Jackson, Tennessee. 

And we are technically outlooked for a low chance of isolated thunderstorms becoming severe today, by the Storm Prediction Center. The odds of any one spot getting a storm that reaches severe limits today is about as low as it would be on a typical summer's day. The exception might be in far Northwest Alabama, where some stuff out West could sustain long enough today or tonight and make it in there while still at severe limits. Overall it does not look like a big deal. 

We'll see scattered showers and thunderstorms off and on the rest of today and could even see a few tonight, but the majority of them will stay under severe limits and just bring us more rain that we need before we get into the heat of summer. High today should get to about 84. 

Tomorrow looks like basically the same thing around here, scattered showers and thunderstorms, a mix of sun and clouds, not raining all day. High should be about 85-87, and the Low should be about 65-67 range. 

And our chances of any severe weather here tomorrow are slim to none. Because of the way the front is shifting around and our ridge here, looks like just general rain and thunderstorms, chances of anything severe is low even in Central and South Alabama, but out in the Plains, it looks like they may be dealing with another tornado outbreak. Looks like it will be centered on Oklahoma and Kansas. 

Then on Sunday, during the day we probably will see little or no rain. We'll just cook up to the upper 80's (morning Low should be in upper 60's) or even 90 for some spots, probably the bigger cities. But Sunday night we will have to watch, when thunderstorms will likely be moving in, maybe a cluster or a squall line, and may be severe. 

The latest run of the NAM makes it look like this will be supercell thunderstorms that form into a squall line between about Midnight and Daybreak as get into Monday morning. 

Technically since we're on Daylight time now, these graphics are valid at 1 AM, 4 AM, and 7 AM. 

At 1 AM it is showing ample unstable air and turning of the winds even at the lowest kilometer of the atmosphere to support severe thunderstorms capable of large hail, damaging winds, and isolated tornadoes. The severe weather parameters look a little better in Tennessee than in Alabama, but all of us need to take the threat seriously. 

The combination of unstable air and wind shear does look somewhat concerning as we go through the dark hours of the morning to daybreak or so, more for Tennessee, but also for Alabama counties, North Alabama. 

And any time it is showing Significant Tornado Parameter values in the 2-5 range, that gets my attention. That is fairly significant. Definitely looks like there will be a chance for tornadoes with at least some of these storms. And if this guidance is right, couldn't rule out a few instances of some people getting fairly significant storm damage. 

But we have to look at more than just one model and have to take all the parameters together before deciding on the overall threat.  

And I just had a long interruption . . . so will pick up this forecast discussion where I left off. 

I was getting ready to compare the NAM guidance to the SREF. A lot of people say the SREF is outdated, and I forget exactly what kind of ensemble approach it uses to generate forecasts. But I've found it very useful over time, not only for severe thunderstorms but for that snowstorm we had back in January, it gave some of the better guidance. 

It continues to show the better onset time at about 10 PM Sunday night instead of after Midnight like the NAM has been advertising so far. To my mind, this would increase the chance of supercell thunderstorms getting going ahead of the main squall line. This is showing pretty strongly unstable air, with CAPE values of about 1,500 j/kg or even 2,000 there just across the Tennessee border. Lifted Indices get down to about -5. 

The storm relative helicity values get up to 200-250 m^2/s^2 for many of us at 3 kilometers. And down in the lowest kilometer of the atmosphere, we still have values of about 200 units. As a rule of thumb you only need about 150 to support tornado development at that lowest level, 200 is a good baseline for the 3 km reading. 

The Supercell Composite numbers start to ramp up, and so does the Significant Tornado Parameter. But this guidance is a little more conservative than the NAM. The NAM can get carried away with scary parameters sometimes. And this usually is more balanced. We see an STP value of about 1-2 around here, with only a small pocket of a 4 value in Southern Middle Tennessee. 

So this looks like a setup for severe thunderstorms capable of large hail, damaging winds, and a few tornadoes across the region. They may be more isolated, at least down on this side of the Alabama/Tennessee state line, but it is a close call. Both models are showing that idea where the tornado threat might be enhanced at some point, even if it looks more likely for the Tennessee side. And I'm inclined to allow for the possibility of any of us being fair game for maybe a few hours where the tornado potential becomes enhanced. And with this kind of strong instability, if we get any storms that are supercellular at first, before the line (or cluster, MCS) forms, I wonder about the potential for extra-large hail. 

Those details will be fine-tuned more tomorrow when the Storm Prediction Center outlines the specific threats for different areas. 

As of right now, considering everything, including the most likely track of the surface Low, it looks like the best chance of really organized severe thunderstorms, with potential for significant impacts, is going to be focused on Illinois, Southern Indiana, Eastern Missouri, and at least Western parts of Kentucky. In or near that hatched area is the main focus. Most of us in the Tennessee Valley are under the more general 15% risk area for severe thunderstorms that could still become organized. And they are still dangerous, of course. And even those of us in that marginal 5% threat area will need to keep an eye on things and see how things trend as we get closer to the event. 

Monday is when the front will pass through the region, Monday and Monday night. Any severe weather should be over with for North Alabama or into Tennessee in the morning hours. But we may have scattered showers and even some thunder lingering throughout much of the day. I'd put the rain chance at 40% lingering showers. High should be in mid/upper 80's (probably mid-80's unless we just clear out a lot before sundown) and Low near 70. 

Then high pressure moves into the region on Tuesday, and we quickly become mostly sunny again. The latest model guidance is showing a High in the lower 80's, Low in the lower 60's. 

Wednesday looks sunny with a High near 80, Low in the upper 50's, very dry air. The GFS is wanting to show some moisture now and throw a monkey wrench in things, but it does not look sensible and is not supported by the ECMWF. 

Thursday it looks like the high pressure will be centered up over the Great Lakes, and down here we will stay mostly sunny with a High of 80 or so, the Low still down in the upper 50's, some cool morning for the end of May. 

Next Friday is the very last day of the month, and we'll stay under the influence of high pressure, sunny skies, High in the lower 80's, Low near 60, low humidity levels. 

As we get into June, we can forget about our severe weather season, but this hurricane season this summer/fall is expected to be an active one, with record-warm ocean temperatures. 

As of right now, places like Cullman, Jasper, Haleyville, up to Guntersville, Fort Payne, Scottsboro, are only included in the 5% marginal risk for severe weather Sunday night/Monday morning. And places like Huntsville, Decatur, Athens, the Shoals, and all of our bordering Tennessee counties are under the basic 15% risk for severe weather. 

The enhanced 30% risk is way up there in Kentucky and the Ohio Valley for now, probably because of their position relative to the expected track of the surface Low. This may be a system where we get the leftovers, but I would still respect the risk. 

If you get a Severe Thunderstorm Warning (or especially a Tornado Warning) Sunday night, I would immediately get into a small central room (or hallway) on the lowest floor of a sturdy house or other strong building. And if you have time, shield your body from any flying or falling debris, especially protect your head. I think this system will end up including at least a low-end risk for isolated tornadoes, even down into North Alabama. 

And have a reliable way to get warnings, at least WEA enabled on a cell phone, but hopefully a weather radio, NOAA Weather Radio, with batteries in it. 

I actually need to put new batteries in mine, because the cats knocked it off the desk and lost the batteries at some point, also unplugged the thing for a while. 

Stormy is adjusting a little better and is not quite as vicious in the ways she threatens Salem, as he still hasn't given up trying to get her to be friendly. He played really rough with me and clawed me up far worse than she's done. She just wants to be left alone. 

A lot of people got sober during the pandemic, or as it was winding down, but I've found myself tempted more and more toward the bottle. So I'm cooking with alcoholic beverages lately, from time to time, to resist the temptation to drink them. I know that's weird. I'm weird, guilty as charged. But I fried some fish in sangria wine today, and that brought Stormy running in the living room. She was hiding before, but when she smelled salmon, that overcame her fears. And she and Salem were fighting over a specific piece of the fish that I threw down for them in the floor. Even after I threw him a separate piece. And then . . . they ended up not even eating either one of them. I get the feeling that cats don't like the flavor of wine with fish the way I do. Because Salem often sniffed of fish I cooked that way and then ended up only nibbling or not eating it at all. 

Anyway that was a funny episode. 

She actually let me pet her today too, first time since she lived with the woman who donated her. 

First time, she rubbed her head against my hand, but then snarled and slapped me when I tried to return the affection by petting her head. 

And then a few minutes later, when she was lying on top of the cat tower, she let me approach and pet her for just a second or two. And then she started to cry and then to hiss and swat me, basically telling me to go away and leave her alone. 

I so love this cat. She shares my general disgust with the world these days but also has a really sweet side. And I'm proud of Salem for not getting into a brawl with her. Last night I woke up many times hearing her hissing at him and growling because he was trying to be friendly again. And he would just sit there and let her get it out of her system. It is really a lot of fun to watch. 

And I haven't even had her a week yet, I don't think. For the most part I leave her alone, because she is eating, drinking water, and going to the bathroom. I think she'll be a lot friendlier when she realizes this place is safe. 

Rainfall totals will probably average an inch or so for most of us between now and Monday night, not expecting any rain after that in this forecast period. A few isolated spots might see closer to two inches or so. 

The chance for excessive rainfall leading to flooding issues looks low, like if it happens, probably stay isolated. 

Having said that, Western Tennessee is already under a Flash Flood Watch. And there is a Flood Advisory that includes Lawrenceburg. Minor flooding is possible in low-lying and poor drainage areas there in Lawrence, Giles, Wayne, Lewis, and Perry Counties. I'll go ahead and post the details as a separate post and then link to it here. 

And that's about it. 

Well a couple more notes:

Obviously it's a good time to go over your severe weather safety plan, so here is the spill I wrote about preparedness earlier in the severe weather season. 

And if you'd like to help out with the relief efforts in Iowa, where they had at least an F-4, maybe an F-5 tornado the other day, here is a link to that town's community relief site. Really appreciate the meteorologist who shared that information with me when I was looking for a way that would actually help, with no pocketing of the money, but I never know if these people want to be identified on a public forum like this. 

Oh and by the way, Reed Timmer got the best video of that tornado ever . . . as usual . . . and is being as modest about it as usual. Seriously, his video and the others are worth seeing if you're fascinated by those kinds of things. At this point, I sort of enjoy them, but I am also tired of all the destruction this year. Let's at least have some variety in how it happens, like a really good hurricane that just wipes a city off the map. If we're going to get off on the destruction, I think it needs to spice things up first. Though granted those storms are awe-inspiring and even beautiful when seen from a safe distance. 

If anybody looks at the time stamp on this, yes I did spend several hours finishing it, but I got sidetracked by a lot of other stuff . . . changing lightbulbs, getting groceries . . . et cetera. Not even I'm obsessive enough to take that long on a weather analysis if undisturbed. 

Hope you stay safe Sunday night, regardless of how mild or how organized an event it turns out to be. Wherever you'll be for the holiday, stay aware of the weather from time to time, and plan ahead of time what is the safest place you could go if a severe thunderstorm or tornado does threaten. 

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