Some folks in Central Texas might have been a little confused as to why the 12Z HRRR was such a wet blanket when it came to snow chances. Instead of snow, the HRRR gave a pretty nasty combination of sleet and freezing rain:
Source: TropicalTidbits
Here's the 12Z HRRR model sounding valid for 12Z Tuesday for San Antonio / Bexar County.
Source: TropicalTidbits
Well that looks entirely below freezing. What gives? Notice the area where the dew point lines up with temperature. That's where the air is saturated, and approximately represents the depth of the (modeled) cloud. It extends from about 850hPa at the bottom to 650hPa at the top. Throughout this cloud, temperatures are between -6C and 0C. Despite the below freezing temperatures,
clouds at these temperatures tend to be mostly composed of supercooled liquid droplets,
rather than ice crystals. As a rule of thumb, you need cloud top temperatures of at least -10C to get a decent chance of ice crystals to fall through the cloud, leading to more snow production. Unfortunately, the atmosphere at those temperatures is quite dry above 600 hPa (in the HRRR). Notice also how vertical motion (bars on the left) is maximized within the lower cloud deck, but tapers off as you get into the heights more suitable for snow production. That also makes it difficult for snow formation.
So, in this particular case, frozen precipitation type relies on the supercooled liquid water tumbling around, coalescing, and hopefully being able to freeze into ice. This is why even with a profile entirely below freezing, freezing rain and sleet can still be entirely probable outcomes.
To the east, the situation is a little different. Here's an isentropic model analysis from the 12Z GFS for the same time. This gives you a sense for how air moves vertically. Follow the wind direction illustrated, and note the pressure (cyan lines) as you follow the path of air. Check out Central Texas... those barbs are more parallel to the isobars, suggesting less vertical motion. But check out the air flowing up and over the Houston area. Those barbs cross the isobars into lower pressures, meaning that air is rising quite substantially!
Source: TropicalTidbits
This increase in vertical lift over East Texas relative to Central Texas means more moisture is able to be thrown up to higher altitudes to the east, giving a higher chance of getting more moisture into the cold temperatures that more suitable for snow production (the dendritic growth zone, or DGZ). We can see this in the 12Z HRRR cross section, which shows moisture reaching higher into the atmosphere, and, critically, into that 500-600 hPa level where temperatures are cold enough to support better snow formation!

So, for Central Texas, snow-lovers will be hoping that vertical motion is higher over Central Texas than what's modeled here.