Tuesday, February 28, 2023

Severe Weather Possible Mainly Thursday into Friday

Today (High 77): Sunny. Light winds from the Southwest. 

Wednesday (High 78, Low 56): Partly to mostly cloudy and breezy with isolated showers/thunderstorms possible during the day, then rain and storms becoming likely at night. Any storms that form may be strong, and some may even reach severe limits.

Thursday (High 75, Low 63): Thunderstorms likely - some possibly severe. A few severe thunderstorms cannot be ruled out during the day, but the main threat for organized severe weather will be in the overnight hours. 

Friday (High 70, Low 60): Lingering showers and storms early. 

Saturday (High 60, Low 41): Mostly sunny.

Sunday (High 62, Low 37): Sunny.

Monday (High 67, Low 40): Mostly sunny. 

At 4 AM skies are clear and winds are calm in Cullman, with perfect visibility and a temperature of 54 degrees. The dewpoint is 41, making the relative humidity 63%. Pressure is 29.84 and steady. Our Low this morning was 50. Jasper had a Low of 43 and is now at 45 degrees with visibility of 9 miles but mostly clear skies and calm winds. The dewpoint is also at a temperature of 45, making their relative humidity 100%. Pressure is 29.84 and rising. Haleyville got down to 49 this morning and is now at 50 degrees with clear skies, visibility of 10 miles, and calm winds. Their dewpoint is 41, making the relative humidity 71%. Barometric pressure there is 29.85 inches and rising. That's 1009.7 in millibars. 

So we catch a break in the action today, with sunny skies expected and a High near 77. Winds should be light from the Southwest. 

But that same storm system that is bringing snow to much of the rest of the country is going to bring us some severe weather potential, and now it is looking like some of it could occur as early as tomorrow. So let's dive right in. 

It still looks like any showers or storms tomorrow afternoon and evening will stay isolated, about a 1-in-5 chance of any one spot getting wet. But then at night, rain becomes likely, and some isolated thunderstorms are possible in the mix. And some could reach severe limits. The best chance of that is from Northern Mississippi back into Southern Arkansas. Around here in North Alabama and Southern Middle Tennessee, we only have a marginal 5% risk of damaging winds or large hail in some storms, and the tornado threat is looking minimal here for this time period. 

Expecting a High near 78 tomorrow. Tonight's Low about 56. Winds will pick up tomorrow and tomorrow night even outside of specific storms, gusts up to 20-30 miles per hour will happen for some people. 

The main event is Thursday, and it's mainly Thursday night we'll have to watch for severe weather potential. The initial supercells are expected to form back over East Texas, Southern Arkansas, Northern Louisiana, and Western Mississippi. These have the best chance of producing really significant damage. This could end up being a severe weather outbreak. As of right now, it is looking like in the Tennessee Valley, we may get the leftovers after the storms form into a squall line later Thursday night into Friday morning. But even if it is folks to our West who get the worst of this system, this threat is well worth respecting. We can have organized severe thunderstorms capable of producing damaging winds, large hail, and tornadoes, even if it is in the form of a squall line rather than discrete supercells out by themselves. They had a rough squall line the other night in Oklahoma that mainly did straight-line wind damage but also had some supercells embedded in it that produced tornadoes. So let's take this seriously even if we end up being in one of the lower threat levels, the way it is looking right now. That 15% risk is still the basic risk for severe weather. 

Look for a High of about 75 on Thursday, Low of about 63. It is going to be windy on Thursday, at least by the night hours. The wind fields with this low pressure system and front are going to be impressive. So even if our unstable air is limited, the combination of that strong wind shear and the strong source of lift along the front can probably overcome that to produce severe weather, perhaps a fairly significant round of severe weather. 

If I have time to post another update this evening or tonight, then I'll try to go into more details and show more of my own reasoning about the forecast, and guess at the timing of the several rounds of severe potential we may have between tomorrow afternoon/evening and Friday morning. For now I'm just showing the broad brushstrokes and explaining what the experts are forecasting. 

I'm having some technical issues, and I do not know if they will be resolved by Thursday or not. If they are, I may be able to provide some real-time updates on the storms as they move in. And I may try to wing it anyway. That's what I've been doing with the forecasts the last two or three days. It takes longer than usual to do graphics and organize everything right now. 

After daybreak on Friday, we are still under that basic 15% severe weather risk, which extends all the way through Georgia and into the Carolinas. The storms are expected to be over by about Noon though. This is looking more and more like an overnight/early morning event. And most people will be trying to sleep or just getting up for work if this verifies. That's why having a weather radio is important. If you know somebody in the path of a tornado or really bad storm during this event, maybe call and wake them up before it gets to them. They might fuss at you, but it could keep somebody from getting hurt. Most people involved in meteorology kind of dread these overnight events, because an awful lot of people do not know what's going on and have a way to wake up if they are in the path of a severe storm or a big squall line of severe storms. 

Anyway it is now looking more like a High near 70, Low near 60 for Friday, and like I said, gradual clearing by about Noon. Should stay breezy throughout the day. 

And the temperature guidance behind the front is not trending as cold now. We turn mostly sunny for Saturday but the High should be about 60 instead of in the 50's as previously thought. Overnight Low about 40 or so. Then on Sunday, sunny, start the day in the upper 30's, so still sort of a cold morning, and then warm to the lower 60's. And then Monday, mostly sunny and the High quickly rebounding into the upper 60's, Low staying about 40 or so. It'll be at least Tuesday before we have to bring back rain chances, much less any chance for any stronger storms. But tomorrow through early Friday, we will have to watch. Tomorrow's threat, even at night, looks very low around here, but something isolated could go severe. There may be more than one round of severe weather Thursday, but the main threat looks like Thursday night through Friday morning, the hours when almost everyone is either asleep or going to work. And Thursday/Thursday night does have the potential to be a severe weather outbreak, at least for some places to our West, that were shown in that hatched area on the map above, that had the "Enhanced Level 3 Risk" in the basic outline, and then the map under that showed the percentages and the hatching. Even if we are not in the highest risk area (as of yet . . . forecast may be fine-tuned over next day or so), it is well worth taking seriously. Let people know that this could be a serious situation with potential for damaging winds, large hail in thunderstorms, and potential for a few tornadoes in the region as well. Even if they are tornadoes embedded in a squall line, instead of from storms that are totally out by themselves, any tornado is dangerous. And sometimes you can get significant damage from one even if it is in a squall line. It's better not to play guessing games about how damaging a storm is going to be. But to take shelter before it gets to you. And even if it is damaging straight-line winds in a thunderstorm, sometimes those can do damage similar to a tornado, and pose a threat to life. The way this is looking right now, it could be an unusually potent squall line. After what they had out in the Plains the other night, I'd rather not fool around with it, gonna' take it seriously. 

Until we get to the weekend, the weather this week is a headache. We may see between 1-3 inches of average rainfall totals, higher amounts generally across the Tennessee border. And by the time Thursday gets here, some places may already be having some issues with flash flooding. And when you have a lot of rain like that, it can make it easier for trees to come down. So some of us may be in for a wild ride. After about midday Friday, things calm down for the rest of the forecast period. 

You can use these maps as a general guideline for making plans, but the idea for now is that all of us have a basic risk for severe weather on Thursday, mainly overnight into Friday morning. So everyone needs to be prepared, don't wait on a higher threat level to be upgraded later before taking it seriously. We could get a few severe thunderstorms before Thursday night, but that is expected to be the main event. 

Need to be able to get into a small central room (or hallway) on the lowest floor of a sturdy house or other strong building in advance of these storms, and not get caught in a mobile home. Anybody driving those hours for work needs to try to plan to be able to get into a building that will be open for shelter if severe weather approaches. Seriously, a lot of our serious injuries or even deaths now still come from simple things like trees coming down in the road where people are driving, or a tree falling on a trailer. Now the other night in the Plains, they got by without anyone losing their lives, but did have about a dozen people injured. So please encourage the people around you to use good sense and do whatever is within their means to stay safe during this event, whatever it ends up doing, and where. 

Lately I wrote a thorough post about severe weather safety, so linking to it here while I'm thinking about it. I think it may still need some editing, but for now, it's what I've got here. You can also look at the official government advice on severe thunderstorms and tornadoes. They also have a good page on flood safety

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