Sunday, March 31, 2024

Warm and Breezy Tomorrow, Severe Thunderstorms Possible Tuesday

FORECAST:

April Fools Day (High 80, Low 60): Mostly cloudy. Warm and breezy.

Tuesday (High 78, Low 66): Thunderstorms likely. A few storms may become severe. 

Wednesday (High 60, Low 45): Mostly sunny. Breezy and turning much cooler. 

EXTENDED OUTLOOK:

Thursday (High 59, Low 37): Sunny.

Friday (High 62, Low 33): Sunny. 

Saturday (High 66, Low 35): Sunny. 

Sunday (High 70, Low 38): Sunny. 

PRONÓSTICO:

Lunes (Máxima 80, Mínima 60): Mayormente nublado. Cálido y ventoso.

Martes (Máxima 78, Mínima 66): Probabilidad de tormentas eléctricas. Algunas tormentas pueden volverse severas.

Miércoles (Máxima 60, Mínima 45): Mayormente soleado. Ventoso y volviéndose mucho más fresco.

PERSPECTIVA EXTENDIDA:

Jueves (Máxima 59, Mínima 37): Soleado.

Viernes (Máxima 62, Mínima 33): Soleado.

Sábado (Máxima 66, Mínima 35): Soleado.

Domingo (Máxima 70, Mínima 38): Soleado.

DISCUSSION:

Skies ranged from mostly sunny to mostly cloudy across the Tennessee Valley throughout the day today. I think it'd be fair to call it a partly cloudy day. It was definitely a breezy day as well, with wind gusts up to 20 miles per hour common, those winds generally being out of the South or Southwest. And it was a warm Easter this year. The High in Cullman was 77, and the Low was 52. By the way, that's the city I forecast for, even though I do try to pay attention to our neighbors in North Alabama and Southern Middle Tennessee. I hate it when the computer models get it right, and I was wrong by just one degree. I second guessed the general consensus of computer model data and forecast a High of 78 today. But 77 is close enough, eh? I agree with Tim Coleman, that you can beat the models, if you use your brain. But . . . sometimes the models still get it right instead. And hey, we do rely on them a lot. 

Back to the observations, the High was 79 in Jasper today after a morning Low of 50. Somebody in my family used to say it stayed hotter down that way because that's where all the wicked people are. I'll leave that to local residents to judge one way or the other. And yeah, I'm having a sense of humor tonight, because I reached a point of exhaustion hearing people arguing over transgender rights and the sanctity of the Easter holiday. I started to offer my opinion on all that last night, but fortunately for all of us, thought better of it. There is too much to sort out in the world these days, and I can't save the whole thing. If it needs to be saved, I really will leave that to the Divine. Which I most assuredly am not. Very mortal, very flawed guy writing these weather discussions, you can count on that. But seriously, I hope everyone enjoyed the holiday to an extent, whether you made it to church, or got some chocolate eggs (or better yet, a whole chocolate bunny) or it was just another daily grind for you. Let's not forget, an awful lot of people don't get these holidays off work. Lest anyone from Jasper think I'm trashing on them, instead of just having a sense of humor about the things people say, they have an awesome radio station that I'm tuned in to right now, listening to Coyote J. Calhoun's Cemetery of Rock. It's not as great as his old show The Edge, because it doesn't include new music, but let me tell you, those old songs from the 1960's through the 90's sound better than you've ever heard them. And he is still the great DJ he's always been. So glad he is still around and still feels like sharing his great musical tastes with us. Even "Susie Q" by Credence sounds full of new life with these remasters he digs up. And I mention that station and show for a reason: A month or two ago, they suffered a bizarre theft, and are still raising money to replace their antenna and transmitter that was stolen. Once in a while, I like to offer them a helping hand in what way I can, which is just reminding people of the situation. And that they are a great station. I also want to salute Jay Fuller from Live 95.5 FM Cullman for openly supporting them both financially and in spirit. That's another great station, with the bonus that they do play new music. Though I can understand a station wanting to cut things off at about the year 2000 for rock music. You do have to sift through a lot of junk to find good rock music after roughly that time. But it does exist. And that's why I skip around stations and also use Pandora Radio. 

If I don't quit yapping, we'll never get through the observations and on to the forecast discussion. So sue me, I had some hot cocoa tonight. I know it doesn't suit the weather now, but it is not as fattening as Coca Colas. And I did not eat any chocolate eggs today. So I got my fix from a cheap, harmless beverage that gives me a pleasant buzz, totally legal and just enough to lift my spirits for something like a weather forecast and an evening of wonderful music. 

Haleyville had a High of 76 and Low of 57. Decatur had a High of 78 and a Low of 55. 

By the way, for anyone who finds fault with my "free-form" method of giving the weather tonight, please remember that this is a volunteer effort. It is rare that anyone even donates a dollar or two to this lost cause. It is just something I still enjoy doing even though I dropped out of school a considerable long time ago. If I ever do get a real job in meteorology, I will observe a lot more professionalism. But for now, I'm really tired of being serious. 

Huntsville had a High of 76 and a Low of 56 today. On the other side of the state, Muscle Shoals had a High of 77 and Low of 56. I used to work for a group called Shoals Weather based up that way, who didn't pay me, fired me on a totally bogus bunch of malarkey (I didn't even realize I was hired yet) which I suspect was really personal in nature, and they now call themselves "Tennessee Valley Weather", the name of my old website when I was in college for meteorology. They went so far as to also adopt the exact same screen name on Twitter and exact same web address I used to use. So yeah, I'm pretty sure it was personal. They claimed they had told me that they were a Facebook-Only-Operation, which they never had, and let me go because I wasn't doing Facebook for them, but doing stuff for their website and mine instead. I remember putting together some of their 7-Day-Planners. So maybe I'll get back into this some day. I would never work with any of those people again though, not the ones who were in charge back when I was briefly a part of it. I tried to stay in touch with Drew Richards, since it was Fred Gossage who "fired" me via a tacky e-mail. But he "ghosted" me from then on, before I had ever heard that term. Think he's working for Radar Omega now, which by the way, is a good product, regardless of who's working there. I still prefer Radarscope, better pricing and just more professional and solid in a lot of ways. Now those guys were awesome. I don't remember specific names, but when they were just Weather Decision Technologies, they let me embed their radar for years and years on my website, free of charge. It was an iMap sort of radar, not the later Radarscope format. They had a great weather radio app for smart phones too, but I don't now what ever happened with that. Nowadays I refer people to WeatherCall instead of that. Since it apparently no longer exists. Anyway, looking over to Tupelo, they had a High of 80 and a Low of 58. Memphis had a High of 76 and a Low of 62. They stayed mostly overcast throughout the day. And finally Nashville, home of all the lovable drunks, friends in low places, a place I wouldn't mind living, but more for the great music and culture than the freely-flowing alcohol (which Brad Paisley wrote a touching ode to one time), they had a High of 76 and a Low of 60. Clouds and humidity were a little more plentiful up Tennessee way and out to our Northwest today. 





So we've got clouds moving in again as that high pressure system has slid off into the Atlantic, and now our next system is draped across a huge section of the country, but definitely through the Midwest, Upper Plains, and Ohio River Valley. They will likely be dealing with some severe weather tomorrow, could be somewhat organized. 



Tomorrow should be fine for us, just clouding up a lot and staying breezy. High should be near 80, Low near 60. This is a get-ready day for our next system. Even at night, rain chances are just about nil. 



Then on Tuesday that cold front comes in here, and we will have thunderstorms. Some could become severe, but notice the surface Low is way up in the Ohio Valley. So that may mitigate our severe weather threat. We do still have to watch it though. And more details on that below the main forecast discussion, will do a mesoscale discussion of the severe weather potential so I can give that full attention. This is, after all, the peak of our severe weather season. People actually debate now when the severe season should be around here, where they used to agree on it. People just love to fight over anything these days. But we all agree that April is the most dangerous month historically. In fact a lot of people forget that April 1, 1974 was a tornado event around here. Because April 3-4 was so much worse. But we actually had an April Fools Day tornado outbreak. It was no joke. 


The ECMWF continues to show a slower timing than the GFS and NAM, which if it were to verify, would mean we'd see the storms come in during the evening, possibly lasting into the night hours, instead of getting started during the daylight hours. Of course we're on Daylight Saving Time now, so evening doesn't necessarily mean we're dark yet. 

Going to forecast a High of 78 and Low of 65 for Tuesday. And remember, some of these storms may become severe. Even if you don't go down and read the details, just be aware that a few storms could be severe, and you do need to be prepared in case that happens, especially if you live in a mobile home and would need to get to a sturdier structure ahead of any severe storms. 



We quickly become mostly sunny again on Wednesday, and we'll stay breezy behind the front. The airmass will modify quicky, a High near 60, Low near 45. 



Thursday looks great, sunny skies, High near 60 again, some places might even have a hard time making it there and stay more like 58 or 59. The morning will be a bit colder with better radiational cooling overnight, the Low in the upper 30's. That's just how it is this time of year, temperature goes up and down a lot in a hurry. 



Then high pressure in place again on Friday, so sunny skies again, really low humidity levels, and another cold morning. We'll get down into the lower 30's and likely see widespread frost Thursday night/Friday morning. If you want to get to freezing, probably head up to around Nashville, but even back here at the ranch, it may be a close call for some locations. 

And then we warm up to the lower 60's for the afternoon High. 



And the clear skies continue into the weekend. Saturday looks sunny with a High in the mid-60's, Low in the mid-30's. Again with these temperatures, have to look out for some frost. If you really want to be safe, you don't plant any sensitive crops around here until about the second week of April. 



And we stay under the high pressure next Sunday, a week from today, with sunny skies and a High near 70, Low near 40 or at least in the upper 30's somewhere. 

So overall it's pretty good news for this forecast, especially for April, just a few bumps in the road. Let's talk about the main one. 


But first, just a quick note that most of us will only see an average of up to about a half-inch of rain for this forecast period. And Tuesday is the only day that rain is expected. 

Unfortunately it is expected to come with some strong storms. 

So let's talk about that. 

MESOSCALE DISCUSSION:

As we get close to Tuesday's potential severe thunderstorm event, it looks like the SREF has a pretty good handle on it. 




Dewpoints are expected to get up to at least 65 degrees across much of the area, so there's your instability, and wind shear between 0-6 kilometers is expected to be between 50-60 knots. This is at 4 PM CDT. So that's plenty of wind shear and sufficient instability to support some severe thunderstorms. 



The surface CAPE is expected to be 1,000 joules or more, notice some values of 1,250 j/kg in Tennessee, so we'll be moderately unstable by that criteria. Another measure of the wind shear, the 3 km Helicity, is a little less than what we'd typically look for, for an organized tornado threat. Usually we'd want to see about 200 units here, and this is showing values in the 100's. So that is a clue that damaging thunderstorm winds may be a greater threat than any threat for tornadoes around here. So let's keep looking for more clues. 



The Lifted Index goes down to about -5 though, which is some pretty strong instability. The theory behind that parameter is that you take a parcel of air at the surface, its temperature, and compare it to a parcel way up in the upper levels of the atmosphere. 

Usually if you subtract the difference, you'll get a positive value, since air cools as it rises upward. However, the updrafts you see on a severe weather day are really warm air rising quickly. So if that value is negative, warmer air aloft than at the surface, then the air is unstable. And a value of -5 is definitely enough to start getting pretty concerned about. We have to take all these parameters into account together, but that one gets my attention. 

Still the Helicity values at the lowest kilometer of the atmosphere are a little below what you'd typically expect from a tornado setup. So this continues to suggest more of a threat for straight-line damaging thunderstorm winds and some potential for large hail as well. For hail to be severe, it has to reach the size of a quarter, inch in diameter. 


It is worth noting though, that the Significant Tornado Parameter (which is calculated with a specific equation, takes all factors into account) is expected to be between 1-2 over our region, the higher values more up around far North Alabama like Huntsville and into Southern Middle Tennessee. And notice there are isolated spots once you get up into Tennessee, closer to where that surface Low will be, where the value gets up to a 4, which suggests the potential for maybe a longer-tracked tornado, fairly significant tornado threat. A value of 1-2 usually points to an isolated tornado that, but once you get to 2 or above, you do have to start considering that the tornado threat may be more significant and organized. Again, you can't base a forecast on any one parameter. Have to take it all into account. But I would respect this severe weather threat we're about to deal with, regardless of where you live in the Tennessee River Valley. 



The NAM looks concerning between 4-7 PM, a stout Energy Helicity Index. And if that slower timing of the ECMWF verifies, movement of the front and rain/storms, then that would dovetail nicely with this and with what the SREF is showing. 


Sometimes the NAM makes things look worse than they really are, but still, taking a forecast sounding at 4 PM in Northwest Alabama (clicked on approximately Colbert/Franklin Counties since the EHI was maxed out there, at 2.7 I believe), it is showing CAPE over 2,000 joules, strong instability there, and Helicity values greater than 200 units, even strong turning of the winds at that lowest kilometer of the atmosphere. Supercell composite of 12 and Significant Tornado Parameter of 2-3. And that definitely points to a tornado threat. 


It shows similar conditions around Double Springs at 7 PM Tuesday. The CAPE is "only" 1,600 units instead of over 2,000. But the Helicity values go over 300 units. So that balances out. Similar supercell composite and STP values. Somebody could get some tornado damage if this verifies. 

Analog guidance remains unhelpful for this event. It suggests anything from just strong storms with almost no severe weather in the region to a widespread event with several reports of wind damage, large hail, even isolated tornadoes. Most of the analogs are toward the lower end of that spectrum though, not all that much in the way of severe weather around here. 





Now to look at the official SPC outlooks, tomorrow and tomorrow night will not pose a threat for severe weather in North Alabama or Southern Middle Tennessee. We probably aren't even going to see any rain. But our neighbors from the Lower/Eastern Plains up through Missouri and into the Ohio Valley may see organized severe thunderstorms. Damaging winds, large hail, and isolated tornadoes are all possible over a broad area tomorrow. Not going to affect us, but it's good to get an idea of what it's doing out there. People travel. You might know somebody affected by tomorrow's weather. Notice that hatched area, mainly in Eastern Oklahoma, where unusually large hail up to two inches in diameter is possible. 



Then on Tuesday, perhaps into Tuesday night, all of us in the Tennessee Valley are still under the basic 15% risk for severe thunderstorms. They will outline specific storm modes and those probabilities about 1 AM as we get into Monday morning, or maybe it's 2 AM. Daylight time confuses me sometimes. But anyway they'll get to that overnight, and most of us will see that during the day tomorrow. The only enhanced 30% risk area for now is mainly over Eastern Kentucky. But it does clip parts of Indiana, Ohio, and West Virginia. So again if you know people up that way or will be travelling, it's good to know details like that. A marginal threat for severe thunderstorms stretches all the way down to Mobile and Biloxi. 

You need a reliable way to get alerts on Tuesday, ideally a NOAA Weather Radio with battery backup or a phone service like WeatherCall. At least enable wireless emergency alerts on your cell phone, even if you normally mute them, and if you can, stay tuned to a good source of weather information if this event gets going during the daylight hours, or if you are still up at night. But the great thing about the weather radio or WeatherCall is that it will reliably wake you up even if something does catch you while you're asleep. It is even more effective than a cell phone alert. That weather radio tone is almost impossible to sleep through. 

The basic idea if you get a Severe Thunderstorm Warning or Tornado Warning is to get into a sturdy house, not a mobile home, or some sort of strong building that is properly anchored to the ground. If driving, you want to pull over to the nearest building, even if it's something very simple, like a gas station. Don't try to get up under a bridge. That myth was debunked many years ago. 

In a sturdy house or other building, you need to:

* Stay away from windows. 

* Get to the lowest floor. 

* Try to be in a smaller room like a bathroom, closet, or hallway.

* Make that room as near the center of the building as possible. 

* Cover your body from falling or flying debris, at least protect your head and/or neck. 

And nine times out of ten, you'll be just fine even if a tornado hits you, with precautions like that. But you do have to get out a mobile home if a tornado is coming. Even lying in an unflooded ditch or culvert, or flat on the ground, is safer than staying in a trailer during a tornado. People have survived that way over the years, although of course, that is a last resort. 

It is ideal if you have a storm shelter or can get to the underground part of a basement, but few of us have ideal options like that. Do the best you can within your means, and more than likely, it will be enough to protect you and your loved ones from serious injury. 

And while we have to consider the worse scenarios for Tuesday, overall it just looks like a routine severe weather threat, mainly for damaging winds and large hail, with the tornado threat probably staying on the lower end. So what I've just said might overprepare you for whatever happens. 

If we're really lucky, we might just get another high wind event without much actual severe thunderstorm damage. But I have a feeling at least some of our luck may run out this time, because the air looks like it will be significantly more unstable than it was able to get for the last several events that looked concerning. It's still not worth getting bent out of shape about, just the most common type of severe weather threat we've had many times in April over many decades around here. I'd just rather people err on the side of caution in case one or two places do get a fairly damaging storm. Even if it's just a tree falling on a house, or especially a car or trailer somebody is in, that's a big deal for whoever it happens to. We try to minimize injury and loss of life during severe weather events, and most of the time, that is easy to do. Those freak scenarios people love to play up, where there was nothing somebody could do, are very much the exception. As a rule, if you take basic precautions, you're very likely to survive a severe thunderstorm or a tornado without serious injury. 

And besides Tuesday, the weather looks great. People with crops do need to be mindful of the frost potential later in the week, but no serious concerns other than that and Tuesday's severe thunderstorm chances. 

I shared some salmon with Salem while writing up this spill. He doesn't like the weather turning warmer so far. He is the best cat I've had since I got out on my own as far as taking shelter from the weather though. I had to chase and fight the others. He will run to the closet, follow me, acting concerned. He is always overjoyed to get out of there though. He just has a lot of good sense and is a fine fellow. 

Strong Thunderstorms Return Tuesday

FORECAST:

Easter Sunday (High 78, Low 53): Partly cloudy. Warm and breezy.

Monday (High 80, Low 60): Mostly cloudy. Muggy and breezy. 

Tuesday (High 76, Low 65): Thunderstorms likely. A few thunderstorms may become severe. 

EXTENDED OUTLOOK:

Wednesday (High 60, Low 45): Mostly sunny. 

Thursday (High 61, Low 37): Sunny.

Friday (High 64, Low 34): Sunny.

Saturday (High 70, Low 38): Sunny. 

PRONÓSTICO:

Domingo de Pascua (Máxima 78, Mínima 53): Parcialmente nublado. Cálido y ventoso.

Lunes (Máxima 80, Mínima 60): Mayormente nublado. Bochornoso y ventoso.

Martes (Máxima 76, Mínima 65): Probabilidad de tormentas eléctricas. Algunas tormentas pueden llegar a ser severas.

PERSPECTIVA EXTENDIDA:

Miércoles (Máxima 60, Mínima 45): Mayormente soleado.

Jueves (Máxima 61, Mínima 37): Soleado.

Viernes (Máxima 64, Mínima 34): Soleado.

Sábado (Máxima 70, Mínima 38): Soleado.

NOTES:

It is a good time of year to review severe weather safety

If you want to catch the solar eclipse next week, I refer you to NASA's guidelines

The National Weather Service in Nashville is still doing its Weather101 classes, and at the last one I was able to take (they are online and free, by the way), Scott Unger asked us to spread the word if we enjoyed it. Which I did. So I encourage any of you who are interested to take one of these classes. There are actually two lined up for April Fools Day, this Monday, the morning one on storm damage surveys, and the evening one about monsoons. 

And this coming Wednesday will be the 50th anniversary of the April 3-4, 1974 tornado outbreak, often called the superoutbreak because of what a nightmare it was. If you lived through April 27, 2011, the event in April 1974 was similar, except it was spread out over more states, and a lot of it happened at night, lasted into the next morning. The Weatherbrains podcast had a great discussion about it this past Monday, which I think will continue this Monday. The show included Greg Forbes, who studied under Ted Fujita, the main guy who helped come up with the F-scale for rating tornadoes in the 1970's. Fujita definitely studied the tornadoes from this event. And there was another one in 1977, a really bad tornado that hit Smithfield, Alabama, that he considered rating an F-6. When they originally came up with that scale, the rating went all the way up to F-12 in theory, and they wondered if tornado winds could even get as high as Mach 1. I remember that from an old library book, which also still advised people to open windows if a tornado was coming. (Please don't try that. But they used to think it would keep the house from exploding because it lessened the difference in air pressure.) The original scale was also called the Fujita/Pearson scale. With the Enhanced Fujita scale, there is no allowance for a tornado to ever be higher than an E/F-5. But back in the day, Dr. Fujita theorized that at least an F-6 was possible. Things have come a long way. Another thing to note about the podcast, Kenneth Graham, who is now the head of the National Weather Service, used to be in charge of the local National Weather Service office in Birmingham. Some people might remember, for a while he was in charge of the National Hurricane Center as well. So it is always good to have him as part of a discussion. I actually met Dr. Forbes years ago. He's mostly retired, so I guess he wouldn't mind me saying, he said Fujita would have come out of his grave to upgrade the Tuscaloosa/Birmingham tornado in 2011 to an F-5 instead of the F-4 (or EF-4) rating it ended up with. And in his lecture, he mentioned that the EF-scale had raised the bar in a lot of ways as to what damage it takes for a tornado to get a really bad rating like that. 

DISCUSSION:





At 5:30 PM, skies are sunny in Cullman. The temperature is 75 degrees, and it looks like that is going to be our High for the day. The Low this morning was 48. Our dewpoint is currently 46 degrees, which makes the relative humidity 36%. Winds are from the Southwest at 9 miles per hour, with higher gusts up to 16 mph. The barometric pressure is 30.00 inches and steady. 

And let's take a quick glance around the rest of the Tennessee Valley. First our immediate neighbors, Jasper had a High of 79 and a Low of 41 today. Haleyville had a High of 76 and Low of 49 today, also under sunny skies. 

Decatur had a High of 78 and Low of 51. Huntsville had a High of 77 and a Low of 50. Fayetteville saw a High of 75 and a Low of 52. Winchester saw a High of 73 and a Low of 46 today. And it remains breezy across the region, winds often gusting up to 20 miles per hour. 

So we are still under the influence of that high pressure to our Southeast. At some point Tuesday we'll be dealing with the cold front currently draped over the Southern Plains, Midwest, into the Ohio River Valley. 



Let's start with some good news. Tomorrow looks fabulous. It will be breezy again, but basically just a mix of sun and some clouds, nothing that will seriously hinder anyone's holiday plans. The High will be about in the 76-78 range and the Low about 52-54. 



Then on Monday, we'll be clouding up more and warming up more. The High should get to about 80 degrees, warmest we've been so far this year, after a morning Low near 60. We'll have more of that warm, moist air coming in here. Notice on the upper-air forecast map from the GFS that our wind flow turns back to the West/Southwest even at 500 millibars (about 18,000 feet). The surface winds will be more South or Southeast at times, and those winds bring us warmer, more moist air, keeping us from cooling as much overnight. 

And the idea of having some rain Monday night has pretty much gone away from the model guidance at this point. If we do see anything like that, it should stay isolated. 



Then that cold front sure is looking robust on Tuesday. That looks like a strong jet stream with it. I enjoyed reading over a few of Bobby Boyd's analyses of the situation. Will share only one below. 

Like Greg Forbes, he is enjoying retirement, but still has great thoughts to offer about the weather. 

But let's stay focused on the basics of our local weather for now. Thunderstorms are likely on Tuesday, and we'll have to watch for the potential of severe weather, at least a few thunderstorms becoming severe. More on that below the main forecast discussion. As Mr. Boyd notes in the tweet I embedded above and a few more I remember scrolling through, the main threat may end up being focused in Tennessee along and East of Interstate 65. That is where the trends are leading my thinking anyway. 

Around here we do have to look out for thunderstorms becoming severe, and almost all of us will see some rain or a thunderstorm at some point during the day or night. We will have gusty winds. The High should be in the mid, maybe upper 70's, the Low in the mid-60's. 

The timing of the rain and storms is also still somewhat in question. I showed the GFS above, and the NAM is on board with that timing, where showers and storms are already moving through here in the early afternoon. (18Z is 1 PM CDT.) But the ECMWF continues to show a slower timing, as it often does. And it often gets that right. Will have to monitor the trends of the NAM as the event gets closer. Right now the NAM is trying to see out 72 hours, and it is a mesoscale model, based on data in North America. Those other two are global models that factor in the weather all around the world and so can predict a much longer time-range accurately. Out to 72 hours is about the limit for when the NAM stays reliable, at least that's been my experience. It's really best for about the 24-60 hour time range. 

Even if the European global model does have it right, it would just mean that the main rain and thunderstorms would arrive in the evening instead of midday/early afternoon. That might be significant for our severe thunderstorm potential though, because it would give the air more time to destabilize. And the storms could happen at night for some of us. So those timing differences can be important. 



Confidence in the forecast increases again on Wednesday. I doubt we even see a lingering shower in the early morning. We will become mostly sunny again with a High near 60, Low in about the mid-40's. 



And now with high pressure moving in from the West, much drier air, it looks like we'll be sunny Thursday, starting the day in the upper 30's and only warming to about 60 degrees again, really good shot of cooler air behind this front. 



Then the same basic trend for Friday, we have high pressure over our region at the surface, and at the upper levels, we have Northwest wind flow. That translates to clear skies and a cool day. We'll only get up into the lower 60's, and for the morning Low, most of us will be in the mid-30's, but some of the spots that are typically colder could even dip into the lower 30's, close to freezing. That's certainly the case as you get into Southern Middle Tennessee and up to places like Nashville and Middle Tennessee. But to keep it simple, many of us are likely to see frost from this cold snap. 



Then on Saturday, looks like we stay sunny with still really low humidity levels, but the Low rebounding to the upper 30's, the High making it up to about 70 again. 

Beyond that, the two global models diverge too much for it to be worth showing, much less trying to base a formal forecast on. The GFS wants to bring us some rain chances, and the ECMWF keeps us dry in days 8-10. If I had to bet on it, I'd bet on the European solution here, but even the scenario of rain coming back by Tuesday the 9th of April that the GFS suggests does not look high-impact. I think it's pretty safe to assume we'll see daytime Highs in the 70's and the Low in the 40's, maybe 50's by end of the tea-leaves period. Like I say, I'm not going to include that in the formal forecast up top, because this the month of April, and it shows in the model output. The weather pattern is too dynamic to really rely on a forecast beyond the next 7 days. But you can sort of note the trends. 

Now let's look at the severe weather threat. 

First of all, the main threat for organized severe weather looks to be on Monday, for our neighbors to the North and West. 



From the lower Plains, parts of Texas, up through Missouri and even into the Ohio Valley, severe thunderstorms are possible over a large area on Monday. Around here on Monday, remember, we are not expecting any storms, and even late Monday night into early Tuesday morning, it's dicey whether we even see isolated rain around here. We will probably just be warmer than we're used to, cloudy, and breezy. The main focus for severe weather Monday will probably be in Central/Eastern Oklahoma, into far Southeastern Kansas, into parts of Missouri. That hatching in the 30% risk area means that severe thunderstorms capable of especially significant damage are possible. Some storms there may be supercells, the kinds of thunderstorms that storm chasers like to chase. They could produce especially large hail and also have a higher threat of producing tornado damage. But really anybody in that broad area could see some severe weather on Monday. Nothing to worry about around here. 



Even though like I said, it's kind of dicey whether you can rely on it at 72 hours or so, I'm going to use the NAM to look at forecast parameters for around here on Tuesday. Because at this time range, using a global model doesn't seem right. And the SREF just didn't look right to me. It had the timing all off and was just a big mess, did not make sense with this weather pattern. 

Between 1-4 PM, it does look like we'll have enough instability and wind shear to support severe thunderstorms. 


But then if we take a forecast sounding from down around Smith Lake in Cullman County, it's kind of interesting. The instability is trending higher, you definitely have to pay attention to surface-based CAPE values of 1,500 j/kg or more, and Lifted Indices of -4 or -5. But then the wind shear may be our limiting factor for a bigger severe weather problem with this. We have good speed shear, like if you look at bulk shear or 0-6 km shear, those values are certainly sufficient. But if you look more at the turning of the winds with height, that really is not quite to where we'd want it to be for an organized tornado threat. The Storm Relative Helicity values are less than 200 m^2/s^2 even up at 3 kilometers. You notice it calculates the Significant Tornado Parameter value as struggling to even get up to a 1. So if this guidance is right, we would have mainly a threat for large hail and damaging straight-line winds in thunderstorms, but might mention the chance of an isolated tornado, especially since this is going to be April. 


And for better or worse, I did decide to look at the GFS after all. Its look is similar to the NAM, but there are some differences. 

First off, let's look at a forecast sounding for that area in about Marion, Lamar, Fayette counties in Northwest Alabama where there seems to be an uptick in the Energy Helicity Index at 4 PM Tuesday. 


And this actually does look concerning, where we'd definitely have to include a tornado threat along with the threat for large hail and damaging thunderstorm winds. The instability is strong, and the wind shear, including the directional shear, is also plenty. Notice the 3 km Helicity here gets up to nearly 300 units, and the 1 km, so low-level turning of the winds, is close to 200. That is plenty, and it would be a favorable time of day for a tornado to occur. Notice the STP value is in the 1-2 range here, which is not overwhelming, but still worth taking seriously. This still doesn't look like a tornado outbreak per se, but I'd be curious to see if any of the other models like the NAM or even shorter-term models like the RAP or especially the HRRR were to pick up on that trend as we get closer to the event, like what if the parameters do become extra-favorable for a tornado in that general area. If storms scare you, please don't get hung up on this. This is nerdy babble from someone who gets hung up on details. A lot of these model trends never play out. And this situation is so uncertain that I really do feel like a nerd for noticing this. 


If you take a forecast sounding from around the junction of the three counties around here - Cullman, Walker, Winston - about at Smith Lake, then the GFS is showing things a little closer to what the NAM was above. The helicity values are stronger, just enough to have to be concerned about a tornado potential in the mix, but also, the instability is only looking moderate. We see surface CAPE struggling to get to 1,000 units at 4 PM, where the NAM had us in excess of 1,500 units. If you look at Lifted Index, it also does not look as unstable. 

So this would translate to basically what the NAM was showing, as far as the tornado threat saying marginal around here. The difference would be that via the NAM, our threat for large hail would be a little more of a concern. 

There are still a lot of details to iron out, even though it's only three days away now. The ECMWF was showing a slower timing of the front and rain/storms ahead of it, and if that were to verify, then we could see more unstable air than the GFS suggests here and might be in for a stormy evening/night, where we'd have to rethink the whole thing as far as how the wind shear and the timing of the lift of the front will coincide with that stronger instability, if we get it. 



The ECMWF doesn't have as many graphics in the public domain that are easy to use to do local severe weather forecasts, but unless the NAM (and then the other mesoscale models) keeps trending more in line with the GFS, I do have to consider how often its slower timing verifies with systems like this. And it is showing dewpoints in the mid-to-upper-60's between 1-7 PM on Tuesday. And that would be in line with how the NAM was showing similar dewpoint temperatures and strongly unstable air, strong surface CAPE, lifted indices well in the negative range. As far as any concern for a more significant severe weather threat in North Alabama or the bordering counties of Southern Middle Tennessee, this is the only concern I have that could really upset the apple cart and throw us a curve somewhere. 


Overall I agree with the Storm Prediction Center forecast, which just blankets a large area all the way up into the Virginias with a 15% basic risk for severe thunderstorms Tuesday into Tuesday night. They may have to add a more enhanced threat level somewhere, but if they do, they will do that as new data comes in. There really isn't enough information right now to base that on, except some hints that East of I-65 in Tennessee could be a hot zone, like Bobby Boyd was analyzing, and makes sense to me. 


One thing to keep in mind is that even if you are looking at the ECMWF more than the GFS, that surface Low is expecting to pass way up North, in the Ohio Valley. The farther you get away from that center of low pressure, the lower the chances of severe weather, as a general rule. 

And this setup just looks kind of messy overall. It certainly does not have the look of a clear-cut severe weather outbreak. It looks like a setup where a few places in our region may get a more organized or significant chance of severe weather, but for most of us, at least on the Alabama side of this, that threat will probably stay on the lower end. For right now, it looks like the places most likely to have a more enhanced risk of severe weather would be along and East of Interstate 65 in Tennessee, and that risk could clip parts of Kentucky and West Virginia, even North Alabama, like around Huntsville, Scottsboro especially. 


But until we get within less than 60 hours of the event and can analyze the mesoscale model stuff, I think the SPC outlook is spot-on, keeping a broad area under a basic 15% risk for severe thunderstorms. Notice it does include all of North Alabama and Southern Middle Tennessee. And it actually extends all the way down to Birmingham. As well as up to Nashville. 


The National Weather Service in Birmingham has had the foresight to extend that into a marginal risk for severe weather even for some places South of Birmingham, like Tuscaloosa over to Anniston. And I used to make fun of how the national and local offices didn't always agree on where to draw the threat areas. But they are in pretty good agreement anyway. And after a while, I realized that the SPC has a really big job, trying to outline every single potential for severe weather across the country every single day, even if it is marginal. And they have to try to figure out the details. They have to think in more general terms to do that than the local forecast offices. The forecasters who know the local area can pick up on things a lot of times that the national centers might miss. I'm sure it's that way with hurricanes too, like someone who has experience with hurricanes in a certain part of Louisiana might could give a more detailed forecast than the Hurricane Center sometimes. 

Anyway, I agree with the Birmingham office's idea that we're mainly looking at a damaging wind threat with this. It seems like the other local offices, when I was reading through the forecast discussions, said similar things but also said they were going to keep an eye out in case it were to become an all-modes severe weather threat. If the air does become more unstable, we'd need to mention a hail threat in the mix for sure. And the tornado threat is worth keeping an eye on, over the day or two, before the event unfolds. But for the moment, that is looking marginal for this system in North Alabama. 

And just because I'm in one of my obsessive moods, and got distracted from finishing this forecast discussion numerous times this evening, I think before I wrap this up, I'll take a look at things in Tennessee for myself. 



Well one thing that jumps out when I look at it again via the NAM is that it looks like a messy squall line, which makes sense with everything else we've looked at already. 

Not showing it here, but checked the GFS, and it looks about the same. 


This forecast sounding is from Wayne County, TN at 1 PM. This is really strong instability the NAM is advertising, more than 2,000 joules of surface-based CAPE. And the wind shear is just enough to be concerned with a tornado threat. Notice the STP is in 1-2 range. Supercell composite of 4-5 range. 


Then if you look up Northeast of Nashville, along the Kentucky border, the NAM is predicting CAPE of about 2,000 joules combined with more than 200 units of helicity even at the lowest kilometer. And that would spell a fairly significant tornado threat. Notice the Supercell Composite is showing about a 10, and the Significant Tornado Parameter comes up to between 1-3 range. That is definitely getting concerning. This is way to our North, but it's just fun to look at. 

And that makes sense with the position of the surface Low too. 

The analog guidance has a wide range of mainly lower-end or routine severe weather events, but a lot of them did produce severe weather in Alabama, and all modes, including a few tornadoes in some of the events, certainly lots of them had numerous reports of damaging winds and large hail. It does sort of back up the idea that the greater tornado threat might be focused more up across the Tennessee or even up to about the Kentucky border. And that's if we see a tornado threat out of this. 

Don't feel like posting more graphics, but looking at the GFS forecast soundings in TN as opposed to the NAM, it is not nearly as aggressive on the instability. But it is still plenty sufficient to support severe storms. And it agrees with the idea of the kind of wind shear that would support at least a low-end tornado threat. But I'm thinking the tornado threat may be more organized on the Tennessee side, especially East of the interstate. 

And after several hours, off and on, of trying to add a halfway intelligent comment on the other stuff going on in the world, that made the news today, or in recent days . . . I have nothing. 

I wrote several paragraphs, then deleted them all. Then wrote several more, thought I was making sense the second time, and deleted those too. 

I have nothing that is worth saying. 

Have fun with the egg hunts and political wars, whichever you find more fun in. 

July Heat Returns Shortly . . .

FORECAST: Friday (High 94, Low 66): Mostly sunny. Cool in the morning, hot in the afternoon.  Saturday (High 96, Low 69): Partly to mostly s...