Monday, May 6, 2024

Some Storms Wednesday Night, Then a Cooldown

Tuesday (High 84, Low 65): Partly to mostly sunny. Isolated showers and thunderstorms are possible and could become strong. 

Wednesday (High 88, Low 67): Partly cloudy with widely scattered thunderstorms possible during the day. Thunderstorms will become likely at night, and some could become severe. 

Thursday (High 80, Low 66): Showers likely throughout the day. A few lingering thunderstorms are also possible. 

Friday (High 73, Low 57): Mostly sunny. 

Saturday (High 72, Low 48): Sunny. 

Sunday (High 74, Low 50): Sunny. 

Monday (High 77, Low 52): Mostly sunny. 

At 3 PM latest observations show partly cloudy skies in Cullman. The temperature is 81 degrees. The dewpoint is 68, making the relative humidity 66%. Winds are out of the Southwest at 10 miles per hour, with higher gusts up to 17 mph. The pressure is 29.97 inches and falling. It is mostly cloudy and 84 degrees in Jasper. The dewpoint is 72, making the relative humidity 66%. By the way, that also makes the Heat Index 90 degrees. Winds are Variable at 6 mph. The pressure is 29.93 inches and falling. And Haleyville is mostly cloudy and 83 degrees. Dewpoint is 65, making the relative humidity 55%. Winds are SW at 10 mph, higher gusts to 17. The pressure is 29.96 inches and falling. 

And it looks like I picked a good time to hop online, as several thunderstorms in Middle Tennessee have reached severe limits this afternoon, which is kind of a surprise. In fact one is showing enough evidence of rotation to prompt a Tornado Warning. 

That warning is strangely not showing up on Radarscope. But it is for these communities in North Central TN for about 12 more minutes. 

The really crazy action today and tonight is back in the Plains. Particularly in Oklahoma and Kansas, what is unfolding may turn out to be a major tornado outbreak, where people who get hit could see a lot of damage. It's one of those days I hope people have access to a basement or storm shelter, because the ingredients are in place for some of the kinds of tornadoes that can blow a whole house away. They've had several severe weather outbreaks out that way lately, but this one looks more organized and somewhat more threatening. 

Notice they have the relatively rare Level 5/5 High Risk for severe thunderstorms. And then the tornado probabilities are hatched (meaning a decent chance of a tornado rated E/F-2, 3, 4, or 5) with probabilities as high as 30% coinciding with that High Risk area. 

Looks like they cancelled that Tornado Warning early in Tennessee, but notice that we do have some minimal 2% tornado potential around here. Truth is, during severe weather season, you have to stay on your toes. Mesoscale features can change the outlook in less than one full day. 

Those 2% tornado probabilities cover Huntsville and Northeast Alabama up into much of Tennessee, places like Fayetteville, Chattanooga, Sewanee, and Shelbyville. 

The rest of us just have a standard 5% risk for damaging winds and large hail, a lot like you'd see on a summer afternoon. But there is enough spin in the air up to the Northeast to justify the SPC mentioning the chance for an isolated tornado. If anything like that happens, it is expected to be short-lived like the warning that was mentioned above. 

Shifting our attention back out to the Plains, they have a significant threat for very large hail (golfball, baseball sized or perhaps even greater) in some of these supercell thunderstorms. They already have a threat for widespread damaging winds, some of which could get up to 75-80 miles per hour or greater, especially in that hatched area. Which does include places like Wichita and Kansas City. I know some people who live out that way. 

So far the tornado reports today have been spotty for tornadoes that did not last long or do much damage, while there have been a lot more reports of severe hail in Kansas. Supercell thunderstorms have started to form. Between now and the night hours, this map may change to reflect a significant amount of storm damage, including some tornadoes that do stay on the ground a long time and cause a lot more destruction out that way. 

Setups like this are fun for storm chasers but not for most people. The latest Tornado Watch out there, including Oklahoma City and Wichita, is a relative rare PDS watch, particularly dangerous situation. The supercell thunderstorms developing so far are only prompting severe thunderstorm warnings. As Rick Smith from the National Weather Service in Norman, OK mentioned on social media, not everyone is going to get a storm out of this, but if you do, it'll probably be a really bad one. 

Between now and the dark hours, some of this area could pretty much explode with tornado development. 

Since we skipped right over the preliminaries, let's look at severe weather probabilities tomorrow and beyond. Some of them do include our region now. Although the chances are much lower than what we're seeing out in the Plains this afternoon and evening. 

Tomorrow the TN Valley is included in a low-end threat for severe thunderstorms, about what you'd expect on a summer day, where a few isolated thunderstorms could reach severe limits with damaging winds and/or severe hail, a lot like what we've been seeing in Tennessee today. The risk does include all of North Alabama. As far as any organized tornado threat, you'd have to go farther North though, into Tennessee, and really more into Kentucky and other parts of the Ohio Valley. Up in the OH Valley, they also have an enhanced threat for large hail, could be golfball-sized or greater. 

Then on Wednesday and Wednesday night, we'll have to look out for a more organized severe thunderstorm potential around here. The much greater chance for severe weather on Wednesday will be from the Mid-South up into the Ohio River Valley, where supercells will start in Arkansas and parts of Missouri before tracking Northeast. That's where you see the hatching. Damaging winds, large hail, and tornadoes will all be possible in that corridor. 

Around here we'll just have the basic 15% threat for severe thunderstorms, mainly a threat for large hail and damaging winds, although especially considering the time of year, we could see an isolated tornado down this way too. 

Then after about 7 AM on Thursday, the severe thunderstorm threat shifts over to the Atlantic Coast, also an area to watch back in Southern and Eastern Texas. 

Lots of cumulus and cirrocumulus showing up on the satellite imagery, and of course with those stronger storms in Tennessee, some cumulonimbus, thunderheads. 

Got a trough axis with a strong negative tilt along with that warm front and cold front almost occluding there in the Plains. The greatest severe weather threat is just ahead of that frontal system. 

It looks like tomorrow will only feature about a 20% chance of rain. As we looked at above though, the thunderstorms could approach severe limits in places. High should be about 83-84, Low about 65-66. 

For Wednesday will go with a 30% chance of showers and thunderstorms during the day, with rain becoming likely (greater than 60% chance) at night. Some thunderstorms Wednesday and Wednesday night may become severe. They will mainly be part of a weakening Mesoscale Convective System from out West, probably coming from Missouri. As discussed above, the main threats look to be large hail and damaging thunderstorm winds. And some of the activity could last into the very early morning hours of Thursday. The High Wednesday will likely make it into the upper 80's, about 87-88, the Low about 65-67 range. 

Then for Thursday, we should see rain showers most of the day, a High near 80 or so, Low in the mid, maybe still upper 60's. And we could still see some lingering storms, especially in the morning. But overall I think the atmosphere will already have its fuses blown by whatever stronger storms we get Wednesday night. 

Then the latest model runs from both the GFS and the ECMWF make it looks like high pressure moving in, cooler drier air behind this front. It was showing that before, but the idea of lingering rain on Friday is now gone, replaced by the idea of just sunny conditions and the cooler air getting in here sooner. It looks like a High only in the lower 70's, a Low near 60 or perhaps upper 50's. 

Sunny skies again Saturday with a High in the lower 70's, Low dipping down into the upper 40's, very dry air overnight. 

Sunday the temperature might moderate to more toward mid-70's for the High, still a Low near 50. 

Then Monday a High in the upper 70's, the Low not making it much above 50. 

After that, temperatures will gradually warm back into the 80's, and we might see some rain chances come back by mid/late week. But that's highly speculative. Basically the weather looks great after Thursday. 

Rainfall totals will average about one inch for this forecast period. 

Remember the basic ideas for severe thunderstorm safety:

* Have a reliable way to get alerts, such as a weather radio or a service like Weathercall. Don't rely on outdoor sirens. 

* If you get a Severe Thunderstorm (or Tornado) Warning, move immediately to a small central room (or hallway) on the lowest floor of a sturdy house or other strong building (rather than staying in a mobile home). Definitely stay well away from windows. 

Maybe we won't need that around here, but we're still in our main severe weather season, until the end of this month, and it is better safe than sorry. 

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