Tuesday, April 4, 2023

Low Risk of Severe Thunderstorms Tomorrow, Cool and Rainy Pattern Until Easter

Wednesday (High 83, Low 67): Windy and muggy. Thunderstorms are likely in the afternoon/evening through night hours, and a few may become severe. 

Thursday (High 73, Low 62): Rain showers continuing. Breezy and turning cooler.

Friday (High 63, Low 51): Showers likely. Staying cool.

(Extended Outlook)

Saturday (High 62, Low 50): Rain showers likely.

Easter Sunday (High 66, Low 48): Mostly sunny.

Monday (High 71, Low 49): Sunny.

Tuesday (High 76, Low 51): Sunny.

(Notes)

Here are some of the latest tornado surveys from the turn-of-the-month event this past weekend.

The National Weather Service in Nashville is doing Weather101 classes through the middle of May.

(Discussion)





So another severe weather event is getting going in parts of Iowa, Illinois, and Missouri. Where a Tornado Watch is in effect. For now just showers over Arkansas, but that will likely lay down boundaries that the severe storms there will tap into later tonight. Their tornado threat is also significant, and that overnight event may cause a lot of suffering if people sleep through it, expecting to hear an outdoor siren, which unfortunately is how it usually goes. I saw on social media where at the Morbid Angel concert where someone died from a tornado in Illinois this past weekend, someone said that they were trying to get everyone downstairs, but that they had not heard sirens beforehand. People have got to start relying on more reliable ways to get warnings, like at least WEA on cell phones, but preferably something like WeatherCall or most reliable, NOAA Weather Radio. If I owned a concert hall, I'd have one of those just like a fire alarm, consider it essential. Anyway it is probably going to be a rough night for Arkansas. I doubt most people are going to be paying attention. 

But let's focus on the local weather. We had some fog this morning but otherwise were partly cloudy in Cullman today with a High of 84 and a Low of 63. We got a little breezy at times, other times winds were light/moderate, generally staying from the South. Jasper saw.a High of 88 and a Low of 66. And Haleyville got up to 85 after a morning Low of 64. 

That warm front has provided these temperatures today, and even if it is unfortunate for the Midwest and Mid-South, the position of everything worked out well for us today, giving us a break from the rain. Some people might be ready for summer already and enjoy the warmer weather. At the very least, the power companies must like the extra revenue these days bring them. Almost everyone has air-conditioning now, even in trailers. There were times it was a luxury when I was a kid, and we used many different kinds of fans to try to keep the light bill down but also keep from "suffocating" as one taciturn member of my family put it when (in later years) one of us tended to keep the air conditioner set a little less cool than he would have preferred. 

For any children who might be reading, this does not refer to literal suffocation, but was a use of hyperbole on the part of a man I sometimes miss very much, to emphasize how uncomfortable he found the heat to be. At other times, he was fond of saying that it was as hot as forty hells, when he came into the kitchen. This is not considered polite conversation by most, but it is probably not vulgar enough language to get you sent to the principal's office. Of course, these days, kids have worse things to worry about than the principal and his or her angry wielding of the "board of education". Those murders in Nashville are in a long line of tragic events that are becoming all too commonplace. I could use a lot of strong language to express my outrage about that, but I will hand that off to folks like Megyn Kelly and Bill Maher. Even if I find Megyn's rants more attractive. They are two among the few journalists who still show some common sense, and have the courage to express it, instead of towing the party lines. Including not giving publicity to the people who commit these crimes, but instead honoring the people whose lives were taken, the students and the teachers. Anyone who seriously harms a child deserves the utmost contempt. People who are willing to put their lives on the line to protect them from such deranged, pathetic behavior, deserve to be honored. And even though it is a bit of tangent from the weather, if you look through history, the treatment of children has been pretty bad, in our country/culture and in many others. Most of us have tried to improve that, and would like to see it continue to improve, instead of having things like what happened in Nashville recently, or what happened in Texas last summer. It's not like it is anything new for weak, vile people to be allowed to take out all their angst on innocent creatures who are simply vulnerable. We just have new ways of doing it. Without getting into the politics of what should be done about guns, mental illness, the state of morality, et cetera, I'll pass along a quote that I heard lately from Jeffrey Mishlove. (Who does a show these days sort of like Art Bell's old late-night radio show, lots of crazy stuff on there, but a lot of good stuff too if you're willing to sift through it all.) I can't even remember who he was quoting, but I have heard the quote before. The gist of it was: "Before you take one step toward power, take two steps toward ethics." And that is what I feel like is the problem, whether weapons are wielded by individuals or by countries. The power to cause mass destruction carries way more weight than does wisdom or a sense of how to treat each other, which by the way, is something that people should be learning in kindergarten or the first grade. Replace those ridiculously high-pressure exams at such a young age with teaching some common sense about life, and we might actually have a future to look forward to. 




Now about the weather, basically we have another cold front that is going to move through the region and then stall out. We should dry about again some time early next week, but until then, should be in a cool and unsettled pattern. Tomorrow, at least in the evening/night, we'll have to look out for a risk of severe thunderstorms, but this time, it looks on the lower end. 



Tomorrow looks muggy and windy, and I think we'll have a little more cloud cover than today, so will "only" forecast a High of 83. Low of about 67 tonight. By evening we'll have a line of thunderstorms approaching, and through the night hours, some of those storms could be on the strong side, or even get up to severe limits. 



Then on Thursday the front stalls over the region. Rain chances stay in likely range, and a High in the lower 70's, Low in lower 60's. Could still be a little breezy, not expecting any more strong storms, just rain.



The latest model guidance is showing numerous rounds of rain possible all the way through Saturday. Looks like a High in the lower 60's and a Low near 50 Friday and Saturday. Overcast days with periods of rain showers. No severe storms are expected. And you might could figure that out on your own since it's going to be so cool. But as much severe weather as we've had lately, thought it was worth mentioning, this is expected to just be a cool rainy pattern. 



Clearing trend will be Sunday through next Tuesday. 

Easter Sunday we might still have a stray lingering shower or two, but otherwise a mostly sunny day, High in mid/upper 60's, Low in upper 40's.

Air should stay low-humidity and clear skies for Monday and Tuesday, Highs getting into lower and then more toward upper 70's as we start the new workweek.


We could see up to two inches of average rainfall totals for this forecast period. 


The threat for flooding issues looks like it will stay on the low end, but it is something to keep an eye on with a pattern like this. Rain should end by Sunday. 

(Mesoscale Discussion)



The NAM is showing a window tomorrow afternoon where the environment might favor some severe thunderstorms.


But a forecast sounding down around Smith Lake only shows moderately unstable air, with pretty weak wind shear compared to what you'd need for a really organized severe weather risk around here. The helicity values or any indications of turning of the wind with height are especially unimpressive as far as any sort of tornado threat. This suggests a marginal risk for some severe hail and strong winds that might could do some minor damage in a few storms along the line. 

But I took a look at the SREF to double-check myself and make sure I'm not "wishcasting" this to be a more minor threat than what the data is really showing. I'm tired of all the severe weather lately, even if a lot of the worst may have hit other states nearby. So let's put aside my personal preference for us to catch a break and stick to the facts. 





Dewpoint temperatures do look to be sufficient, in the 60-65 range tomorrow evening. This is valid at 7 PM. I think the NAM data above was more like 1-4 PM. Doesn't matter much, the estimated arrival times for the line of storms tomorrow are approximate. 

The 0-6 km shear values are actually respectable, 40-50 knots. This actually does make it look like severe weather will be possible, and might have to watch for any supercells within or just along the edge of the squall line. 




Surface-based CAPE looks like it's in the moderate range of about 1,000 j/kg like on the NAM guidance. Definitely enough to work with, more than we had for the more organized events lately, we had closer to 500-750 joules over much of the area. 

But then we get to the Helicity values up to 3 kilometers, and we are struggling to even reach 150 m^2/s^2. So this suggests a very low chance of any tornadoes forming around here. So probably more of a large hail/damaging wind threat. Remember for hail to be severe, has to get up to the size of a quarter (inch in diameter), and for wind to be severe, has to get up to 58 miles per hour (50 knots). 



Lifted Indices also look marginal, about -1 to -3 degree range. That's where you take a parcel of air, lift it up to 500 millibars (about 18,000 feet) and take the difference between the air at the surface's temperature and if you lifted that parcel up that high. Usually air gets colder as you go higher up, so if you can subtract the air way up there from the air way down at the surface and get a negative value, that means there is a strong enough updraft to make the air actually warmer way up in the clouds than down at the ground. That's why Lifted Index is a measure of how likely the weather is to become severe, how unstable the air is. And it is looking marginal. 

And the the Storm Relative Helicity at the lowest 1 kilometer of the atmosphere, I mean, we had values of about 300-500 m2/s2 for the last two severe weather events around here. And with this, we only have about 100-150 units showing up. I believe the NAM showed even lower values than this. So the turning of the winds with height is just weak with this system around here. 



It would not be impossible to see an isolated supercell thunderstorm or a tornado with this squall line, especially in Northwest Alabama up into Tennessee, but even there, the risk is looking low. 

This is our primary tornado season, peak month of it, so the last thing I'd want to do is lull anyone into a false sense of security with this, but the tornado threat does look pretty low with this system. 



And you can see that in the latest severe weather outlook from the Storm Prediction Center. The tornado threat is minimal until you get to about the Western half of Tennessee, and even that is just a basic isolated tornado risk of 5%. Now as you get up into the Great Lakes region, they do have a decent chance for supercell thunderstorms capable of a more significant tornado threat. The reason for this positioning of the better tornado potential is the surface Low tracking all the way up into Canada as you saw on the maps earlier. We are way South of where the best dynamics are with this system. There were times I'd started to wonder if we'd have any severe thunderstorm threat at all. 



Even the threat for large hail and damaging winds looks on the lower-end around here. Far Northwest Alabama up into Southern Middle Tennessee has a higher threat than the rest of us, but even that is just the basic 15% risk that you'd expect with a routine squall line. Now as you get into Western Tennessee, you do have an enhanced risk of 30% for damaging thunderstorm winds. And up in the Great Lakes region, they have a 30% hatched areas for an enhanced risk of very large hail. Again, that is where supercell thunderstorms could form and carry a threat for very large hail, some damaging winds, and a more significant tornado threat. 


So our threat for severe thunderstorms tomorrow is not zero, but overall it is low. Might want to pay a little more attention if you live up around the Shoals or up into Middle Tennessee, definitely if in Western Tennessee. But for the most part, this is one of the lower severe weather risks we've seen in the Tennessee Valley in a while. It looks like a typical squall line where some thunderstorms could reach severe limits with some severe hail and damaging wind gusts. The tornado threat looks minimal with this one. 

Having said that, if all we get is one storm all day (or especially if it were to come after dark) that knocks a tree over on someone's house, or does significant damage to a trailer where someone didn't know it was coming in time, then we've got problems. And we've had enough problems lately. 

So a few reminders about safety:

* Have a reliable way to get alerts, not relying on an outdoor siren. A NOAA Weather Radio or service like WeatherCall is best, but of course you can make sure WEA is enabled on your cell phone and maybe tune to a good radio station (more likely to cut in with that abrasive sound than a TV station) that reports severe weather. 

* Try to plan ahead so you can be in a sturdier house than a mobile home when severe thunderstorms are getting close to you. Also so that you do not get caught driving through them.

* In a site-built house or other sturdy building, try to get to a lower floor and near the center of the structure, away from windows, away from electrical stuff, and hopefully away from doors that lead to the outside. 

* Consider giving someone a call if they do not know a damaging storm is coming late at night, especially if they do live in a mobile home or other weak structure. Maybe even let them stay with you, if you've got better shelter to offer. 

Hope that helps. Maybe we won't have too many problems tomorrow evening or night. 

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