Let’s start off with the weather that will impact the most folks today. That’s going to be the heat and humidity. For the eastern two-thirds of Texas, today should be the hottest day so far in 2019. High temperatures this afternoon should be in the middle to the upper 90s south of an unseasonably strong cold front. Yeah, I just said strong cold front in June. I don’t get to say that every year and temperatures north of that front are going to be 30 to 40 degrees lower. 90s aren’t much to write home about here in Texas during the summer, but with all the rain we’ve had the soil moisture is still quite high. All that moisture will result in a boatload of humidity – meaning the heat index is going to be in the ‘miserable to downright dangerous’ category today, at least depending on where in Texas you’re located.
Peak heat index values will be between 115 and 120 degrees this afternoon across Deep South Texas and the Rio Grande Valley. I don’t care if you’re used to Texas heat or not 120-degree heat index values can be deadly. Heat index values over 105 degrees are possible from Sanderson to San Angelo to Brownwood to the D/FW Metroplex and points south. Those in East Texas and Southeast Texas won’t get nearly that high today. This will be the first ‘nasty’ heat index day of the summer so some of our bodies may not be acclimated to that kind of heat yet this summer. At a minimum make sure you’ve got plenty of sunscreen if you’re going to be outdoors. You know the heat safety tips and I’m not going to go through them.
Now that I’ve talked about how hot it’s going to be today let’s dive into the thunderstorm forecast. We now have a level 3 risk of severe weather for much of the Hill Country, Central Texas, and North Texas along and south of Interstate 20. Sonora, Junction, Brady, Brownwood, Stephenville, Fort Worth, Dallas, Hillsboro, Waco, Temple, Killeen, Georgetown, Burnet, and Fredericksburg are a few towns included.
A level 2 risk includes Southwest Texas, the northern Edwards Plateau, South-Central Texas, the western Brazos Valley, and the remainder of North Texas. Sanderson, Ozona, San Angelo, Del Rio, Rocksprings, Kerrville, Uvalde, San Antonio, Boerne, New Braunfels, Austin, La Grange, College Station, Fairfield, Denton, Gainesville, and Graham are a few towns included. A level 1 risk of severe weather includes the southern Trans-Pecos, portions of South Texas, and portions of Texoma.
Regional graphics showing the same severe weather outlook. Click on any image for a full-screen version.
The severe weather outlook runs from level 1 up to level 5 with level 5 being the highest. Risk levels are based on the probability of experiencing severe weather within 25 miles of any given point, such as your home. We’ve got an explanation of the risk scale below. You can always see the latest severe weather outlooks along with a much more detailed explanation on the entire risk system and how it’s made in our severe weather dashboard here.
Damaging straight-line winds (or microbursts) will be the primary threat with the most intense storms today. Given the very warm airmass in place along with lots of moisture, there is an enhanced threat of wind gusts over 70 MPH today. Just like the storms in South Texas a few days ago these storms today could produce more significant wind damage. Localized hurricane-force winds over 75+ MPH are a noted threat. Large hail and localized flooding may also occur. If storms grow upscale into a squall line, or we see any particularly large/intense thunderstorms organize, that threat for significant damaging winds over 75 MPH will also increase. Weak low-level wind shear and high cloud bases (thanks to that heat today) will keep the threat for tornadoes very low. The tornado threat isn’t totally zero given extreme instability values, but I don’t think we’ll have to deal with much of a supercelluar tornado threat today.
I don’t want you to pay too much attention to exactly where the lines are drawn. If you’re in or near any of the risk zones this is your ‘heads up’ of an outlook of potentially severe thunderstorms this afternoon and this evening. Storms don’t read maps and don’t care where we draw our fancy little lines. These outlooks are updated five times a day on the day of an event. So now that we’ve shown where we believe severe storms are possible today let’s dive in a bit more and get into the timing.
Our ‘show’ shouldn’t begin until after 3 PM this afternoon. It’s going to be hot and humid south of a cold front. That front should be located across West Texas into Northwest Texas extending northeast toward Oklahoma City. Temperatures north of that front should be in the 50s and 60s with north winds howling at almost 40 MPH. Truthfully, I can’t remember a cold front that potent this late in the season. This is going to be a legitimate cold front and as someone who sweats buckets when it’s over 80 degrees – I’ll take it!
The first storms of the day should get going after 3 PM. I don’t think we’ll see immediate upscale growth into a cluster or squall line. It’ll probably be a similar timeline as to what we saw last week with storms that developed in the Hill Country during the early afternoon, those moved east/southeast for a few hours, and then we saw more storms fire up in the late afternoon into the early evening. That’s when storms were most intense and produced that significant wind damage. While that last event had storms moving off the coast by 8-9 PM – we’re going to be dealing with grumpy storms well into the evening across portions of North Texas, Central Texas, and in the Hill Country.
Again, it’s going to be in the upper 90s this afternoon. These things are probably going to be 50,000 to 65,000 feet tall – they’re going to stop just because of the sun setting. What will eventually cause the storms to weaken this evening is a strengthening cap after 10 PM. That’ll occur as storms move east/southeast through the Brazos Valley and toward northern parts of the Coastal Plains. Now those storms may not completely dissipate, but they should at least be weakening by midnight. Isolated severe weather (damaging winds and hail) will remain possible well into the night.
I can’t tell you specifically where the first storms of the day will fire up. That’ll depend on the position of the cold front by the late afternoon. Another feature that could help spark thunderstorms is an outflow boundary. Storms ongoing across southern Kansas earlier this morning generated an outflow boundary. That outflow boundary, known as OFB from here on out, should be in southern Oklahoma into Texoma by the late afternoon hours. That may help fire up a few storms that could impact North Texas. Otherwise, we’ll just have to watch visible satellite imagery this afternoon to see where things bubble up. I’ll say this – you’ll know there’s a storm coming because they’re going to be over 50,000 feet tall. Once they pop they’ll probably get going in a hurry.
Those attending outdoor events or spending some time on the lake should plan ahead and have a shelter in mind if a thunderstorm approaches. Remember, storms can shoot out lightning over 15 miles away from where it’s raining. If you hear thunder you’re close enough to be struck by lightning. Strong outflow winds from thunderstorms could arrive 10 to 20 minutes before any rainfall. Those strong winds are extremely dangerous to those on lakes – and they’ve proven fatal in years past. Your local favorite television station probably has a free app that’ll notify you if a severe weather warning is issued for your area. Likewise, just keeping an eye on the weather radar would be a good idea too. We’ve got a great (FREE!) interactive weather radar here on our website and in our free mobile app.
Looking past today’s storm chances reveals below-average temperatures for the next several days across most of Texas. That front will continue moving south tonight into Monday before stalling out. Temperatures and humidity north of that front will be much lower. That’ll be noticeable for high temperatures, but also quite nice during the overnights as temperatures drop off into the 50s and 60s (even some 40s in the Panhandle.) It isn’t arctic cold, but it sure beats the 120-degree heat index values expected this afternoon in the RGV.