Looks like the setup is good for strong to severe thunderstorms Sunday through Tuesday morning in Texas. A 500mb trough will eject out of the Pacific by Sunday morning and become cut-off over New Mexico as early as Monday afternoon. With south and southeasterly winds at the surface, and dewpoint temperatures in the upper 50s and 60s across Texas, instability will be great across much of the state for Sunday and Monday. A cold front, associated with the mid-level low will also aid in the lifting for storm development. Along with the surface cold front, a dryline(a boundary separating dry air and moist air) will be intact.
Most of the storms that form Sunday and Sunday evening will form ahead of the dryline(on the moist side, Figure 1). The best chance for strong to severe thunderstorms to form on Sunday will be from Amarillo through Abilene to Del Rio, and east as Monday morning approaches.
Storms that form Monday and Monday evening will be ahead of the dryline, but also along the cold front that will push through the state. The greatest potential of severe weather will be along the I-35 corridor, during the afternoon/evening hours on Monday. Computer forecast models suggest that showers and thunderstorms begin to fire early Monday morning, west of I-35, then become more aggressive by early afternoon through the evening hours, as it pushes east. Surface cyclogenesis takes shape on the lee side of the Sierra Madre Mountains in Mexico Monday afternoon. This will enhance thunderstorms along the cold front by Monday evening. By late evening, this system will become a Mesoscale Convective System (MCS), or linear in appearance. This MCS will stretch from Iowa/Missouri, down through Corpus Christi, as suggested by the 12Z 3/17 NAM. As of right now, the RGV doesn’t look like it will have issues with severe weather due to a capping inversion. However, if a shower/storm or two can break through the cap, it is very possible that it/they can go severe. Once linear, the biggest threats will be hail and wind with the storms.
There is still some uncertainty what the mid-level low will do after Monday. It and the cold front’s location will determine rain chances for central and east Texas on Tuesday. At the moment, it looks as if the MCS and cold front will push across east Texas Tuesday morning and exit the state by Tuesday afternoon.