Nothing in SW Houston. Whoever is seeing "sleet", are you sure it's sleet and not graupel? Sounding has all precip forming in sub-freezing air above 700mb, which should be snow. There isn't any above-freezing followed by another sub-freezing layer (which would produce sleet) indicated. See the sounding below.
Could super-cooled water above 12,000 ft be going directly to ice vs. snow crystals to produce sleet? Or are we seeing graupel, which is partly melted and re-frozen snowflakes? Graupel is round like sleet but much whiter and softer (generally).
This is what graupel looks like:

Latest Houston Sounding:
