All the parameters are coming together for an active day across a large portion of Texas and Louisiana on Sunday. Currently, isolated severe storms are occurring north of the Texas Hill Country, and a few isolated severe storms are possible across central and northern Texas overnight. Large hail, damaging winds, and an isolated tornado or two are possible. There’s a slight risk of severe thunderstorms for parts of central and southwest Texas.
SPC Thunderstorm Outlook (Tonight)
The bigger impact event will begin to take shape around sunrise on Sunday and continue throughout the day. Much of eastern Texas, northern Texas, southern Oklahoma, southern and central Arkansas, and Louisiana have the chance to see severe thunderstorms–including strong tornadoes in some areas (more on this later in the article). The Storm Prediction Center has a moderate risk (a category 4 on a scale of 1 to 5–with five being the most significant category) for eastern Texas and western Louisiana.
SPC Thunderstorm Outlook (Sunday)
Regional SPC Severe Map From Houston/Galveston NWS (Sunday)
A surface-low will move across Texas tomorrow morning into the afternoon hours. This will lift a warm-front into southern portions of northern Texas. Dewpoints to the south of this boundary will be well into the 60s with mid 70s closer to the coast. A potent upper-level low will begin to approach Texas at the same time. CAPE values should be around 2000 J/Kg or greater, and no CAP. This means storms should develop quickly around sunrise just south of the warm-front and will not be elevated to the south of the warm-front.
All storms south of the warm front on Sunday morning will have a great potential to produce severe weather. Tornadoes, very large hail, and damaging winds are possible. The helicity values will favor rotation, thus, likely enhancing the tornado threat from Tyler, Texas to just south of Dallas to about Waco, Texas–and points south and east. The southern and eastern parts of Texas and western Louisiana have the best chance of seeing a strong tornado or two with discrete thunderstorms.
Highest Tornado Threat Sunday Early Morning-Afternoon (Firsthand Weather)
Locations north of the warm-front (north of the DFW Metro and southern Oklahoma will see a hail threat and possible gusty winds). It should be noted, however, that all of north Texas and even southern Oklahoma does have a severe threat, too, just not a high tornado threat. The severe threat will shift shift eastward throughout the day towards the Arklatex area, and eventually into the Mississippi Valley late in the day on Sunday. The storm mode should favor discrete development, transitioning into a squall line for eastern Texas–with isolated discrete cells developing ahead of the squall line just south of the warm-front.
A second area of thunderstorms could develop across north Texas and Oklahoma later on in the day on Sunday as the upper-level low moves across the area. These storms will produce heavy rainfall and possibly hail. It should also be noted, precipitation amounts will be copious tomorrow. Flash flooding is possible across much of the areas mentioned in this article with the greatest chances occurring in highly urbanized areas due to the impervious surfaces (Austin, Dallas, Houston). Please make sure you have a plan in place, and stay weather alert tomorrow. No need to panic, just be prepared to seek shelter if a warning is issued for your area. I will have an update tomorrow morning.