Discussion – 

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Discussion – 

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After 4PM Wednesday: Storms with giant hail threat; squall line for eastern half of Texas tomorrow night

I want to start out by sharing a resource for those experiencing storm stress and anxiety. You might be surprised to know that I personally deal with it when severe weather is threatening my home. Yup, the dude who chases tornadoes was scared beyond belief as a child of storms – and I still deal with that anxiety at times as an adult. It’s a real issue and don’t let anyone tell you otherwise. There are things you can do to empower yourself and take more control over your weather fears. The National Weather Service has put together a great page here. I encourage you to check it out.

Those of you who read our morning blog detailing tomorrow’s severe weather threat know I’m well aware of the heightened concern regarding tornadoes after last Saturday. Let me start off by saying the threat for tornadoes tomorrow is much lower than what we experienced this past Saturday. The tornado risk on Saturday was a level 4 out of 5 – with 5 being the highest. Tomorrow’s tornado risk is at a 2 out of 5. A few tornadoes are possible tomorrow, and while the risk is low, it is not zero. If there is only one tornado tomorrow and it comes down your street it’s ‘your outbreak’.

What I am more concerned about for tomorrow is the threat of extremely large hail. Yup, we’ve entered the season of the ‘dry line’ where storms fire up around 5 PM and are producing baseballs by 6. Let’s dive into it and start out with the latest severe weather outlook from the Storm Prediction Center.

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(Click image for full-screen version)

A level 1 marginal risk of severe storms include the western Texas Panhandle, the eastern Big Country, the eastern Concho Valley, South Texas, the Coastal Plains, and Southeast Texas. Isolated strong to severe storms are possible in and near this risk area. Dalhart, Vega, Amarillo, Childress, Breckenridge, Brownwood, Laredo, Corpus Christi, Victoria, Houston, Galveston, and Jasper are a few towns included.

A level 2 risk – the standard severe weather risk level – includes the eastern half of the Texas Panhandle, portions of Northwest Texas, western North Texas, South-Central Texas, the Edwards Plateau, the southern Brazos Valley, and the piney woods of East Texas. Scattered severe storms are possible. Dumas, Shamrock, Wichita Falls, Graham, Del Rio, San Antonio, La Grange, Conroe, and Lufkin are a few towns included.

A level 3 risk – an enhanced severe weather risk – includes the far northeastern Texas Panhandle, Texoma, North Texas, Northeast Texas, portions of East Texas, Central Texas, and a good chunk of the Hill Country. Numerous severe storms are possible. Canadian, Gainesville, Sherman, Paris, all of the D/FW Metroplex, Hillsboro, Waco, Temple, Georgetown, Burnet, Fredricksburg, Austin, Bryan, Centerville, Fairfield, Corsicana, Palestine, Canton, Tyler, Longview, Sulphur Springs, Quitman, Gilmer, and Texarkana are a few towns included.

Here are some regional graphics depicting the severe weather outlook. It’s the same risks as our primary graphic, but ‘zoomed in’ to help folks locate their location. Don’t pay too much attention to the exact line placements. The severe weather threats stay fairly identical across all three risks. The higher risks mean you have a higher chance of having severe weather in your area. Line placements will typically change some with each outlook update. You can click each image for a full-screen version.

Specific Severe Weather Hazards

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The strongest thunderstorms that develop late tomorrow afternoon will be capable of producing very large to giant hail. Baseball size hail and larger is expected. I wouldn’t be surprised to see the most intense storm late tomorrow afternoon produce softball size hail. Needless to say, you’ll want to keep your vehicles in the garage tomorrow evening. A line of storms later in the evening and overnight may produce quarter to golfball size hail.

Damaging straight-line winds are also a threat with the initial storms, but the overall damaging wind threat should increase by the mid-evening hours as a line of thunderstorms quickly develops from Oklahoma southward to the Edwards Plateau.

Tornadoes cannot be ruled out tomorrow, but the overall threat is low. The highest threat for a few tornadoes will be with initial discrete supercells during the late afternoon hours across Texoma, North Texas, south into the Hill Country. Brief tornadoes are possible with the squall line tomorrow night as it marches its way east across the eastern half of Texas.

Flash flooding will also be possible tomorrow evening and tomorrow night – especially in locations that have saturated soils from recent rainfall. Overall, the threat for flash flooding will be highest across Northeast Texas and East Texas. A new round of stream/river/lake rises will occur this weekend into next week.

This is much more of a hail and wind event versus one where we would focus on tornadoes as the primary hazard. That isn’t to say you shouldn’t take tomorrow seriously. If we end up with one of those mean hailers moving across the D/FW Metroplex it’ll easily result in several hundred million dollars worth of damage. Our friends in Denton and Collin counties can certainly attest to a hail storm’s intensity given that they’ve had like ten in the last five years.

Timing and Detailed Discussion

In this morning’s blog post I discussed the potential that we may see isolated storms fire up in the mid-afternoon across East Texas (well east of the dryline). That potential seems to have decreased.. I can’t rule out a rogue storm tomorrow afternoon in East Texas, but I think the main show will wait until the late afternoon hours back west along the dryline.

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Current weather model guidance is in fairly good agreement that the dryline will be near Highway 281 by 4 PM. It may end up being 20 miles west or 20 miles farther east, and we’ll deal with that tomorrow. The threat for severe weather will exist east of that dryline.

Understand that the time windows and locations I’m about to give could still shift a little, either a bit earlier or a bit later. We expect the cap will hold through the mid-afternoon hours, but that will quickly change as strong upper-level lift arrives around the time of peak heating.

Initial thunderstorm development could occur as soon as 4 PM from near Henrietta to Jacksboro to Mineral Wells to Stephenville to Event. However, I’m thinking it will be closer to 5 PM. When thunderstorms go up they’re going to go up extremely quickly in a very unstable airmass.

You’ll know the storms are developing because their updrafts will look like bombs going off. They’ll quickly climb to 45,000 to 55,000 feet and could become severe with hail within 30 minutes of first developing.

Initial storms will move to the northeast around 35 MPH. Any storm splits (when one storm splits into two) will result in deviant storm motions. The ‘left split’ will quickly move north/northeast while the right-split may move in a more easterly direction at 20 to 30 MPH. We could see several of those splits occur tomorrow, which makes for a messier situation.

With the quick lifting of the cap and strong upper-level lift we could see several storms go up at once. If they can do that over a smaller area that would actually tend to limit their overall organization. No doubt that they’d still be severe, but could help keep hail sizes under the ‘giant’ category. That might be a bit of optimism on my part given the atmosphere is going to be extremely supportive of hailers.

Once storms fire up along the dryline in North Texas they won’t be too far west of the D/FW Metroplex. We anticipate severe thunderstorms capable of producing golf ball to softball size hail, localized damaging winds, and the potential for isolated tornadoes will move into the D/FW Metroplex between 6PM and 9PM (sooner to the west and later in the east, you get the drill). The same timeline goes for those along/west of I-35 across Texoma south to Waco and Temple.

Understand that the second round of severe storms (hopefully in more of a cluster/squall line) may occur after 9 PM and not end till midnight. That means we may have two different rounds of severe storms in D/FW tomorrow evening. I won’t guarantee there will be two rounds, but its certainly possible since the dryline may fire up again after sunset.

The dryline will likely ‘unzip’ with a line of thunderstorms quickly between 8 PM and 11 PM across Oklahoma, Texoma, North Texas, Central Texas, the Hill Country, south into the Edwards Plateau. This would result in a second round of strong to severe storms for those impacted by the ‘first-round’ not even a few hours earlier.

Large hail will certainly be possible with the strongest storms in that squall line given strong instability values well into the night. Damaging winds will become a greater concern too, with a transition over to damaging wind being the primary concern after midnight. Brief tornadoes will be possible with stronger sections of the squall line as it moves east. It is this line that will bring the highest chance of thunderstorms to the eastern half of Texas Wednesday night into Thursday morning.

18Z 3KMNAM: Simulated weather radar around 4 AM Thursday. A line of strong to severe storms will be moving east across the state. The exact timing may still speed up or slow down some. Click the image for a full-screen version.

This squall line could be moving into our I-35 urban corridor from Waco south through Austin, San Antonio, to Laredo between 10 PM and 2 AM with an associated severe weather threat. Hail, damaging winds, a brief tornado, and localized flooding are expected with the most intense segments in the line. It’ll surge east across Northeast Texas, East Texas, the Brazos Valley, into the Coastal Plains, and Southeast Texas from the early morning hours Thursday to near sunrise.

Far East Texas and far Southeast Texas may not have the line move through until after 6-7AM – with some storms still being strong to severe. Flooding may occur across parts of Northeast Texas and East Texas Thursday morning as one to three inches of rainfall on saturated soils.

We’ll be watching as evening weather model data arrives and will share the new severe weather outlook from the Storm Prediction Center when it is released around 1 AM. Much of the TSC group is planning on being out in the field tomorrow.

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David Reimer

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