Several of the MS and LA NWS Offices have mentioned this 'cool' front in their afternoon Area Forecast Discussions.
My understanding from reading the AFDs is that the front should push Rita's remnants toward the NE. Allowing for cool and drier air to take hold. I saw temps into the 50s and 60s, later in the week, for the Jackson,MS forecast area.
I like Clark's explanation better.

edit: I'll throw this snippet in for emphasis on the cool front.
Reference to "Katrina"...should be "Rita".
The mind plays tricks on METS too!

...WILL GENERALLY FOLLOW TREND OF GFS TO LIFT REMNANTS OF KATRINA GRADUALLY TO THE NE BY SUNDAY NIGHT. MAINTAINED HIGHER POPS CENTRAL AND ERN ZONES FOR SUNDAY NIGHT AS THE SYSTEM LIFTS NEAR THE MS RIVER. HOWEVER INCREASED MOS POPS WRN ZONES SLIGHTLY DUE TO UNCERTAINTY OF SPEED OF SYSTEM...KEEPING THIS AREA IN HIGH END CHANCE CATEGORY. MODELS FALLING INTO CONSENSUS THAT UPPER TROUGH WILL CONTINUE EWD SHIFT MONDAY WITH NWLY FLOW AT LOW LEVELS REDUCING PRECIP CHANCES FROM THE WEST. WILL DECREASE MOS POPS SLIGHTLY FOR WRN ZONES BY THE BEGINNING OF THE WORK WEEK....