The strongest blast of cold air of the season will come overnight on Wednesday bringing in chilly temperatures on Thanksgiving. Rather than this being a one or two day deal -- this cold air looks to stay at least through the mid part of the following week.
Here's what the models show:
12z GFS
138 hr

144 hr
Behind the cold front, expect an off and on steady cold rain as we should have a steady overrunning situation last throughout the later portions of this week and into the weekend. Winds on Thanksgiving will be around 20 MPH with gusts over 30. Temperatures will top out only in the low to mid 50s with lows in the mid to upper 30s.
If the temperatures trend even colder, we may even approach the freezing mark here in town -- and a somewhat realistic shot of maybe having some sleet mixed in deep in the Hill Country.
Bundle up, I'll post more as the forecast becomes clearer
