2006 Prius Evaporator Core Freezing?

I suspect that my evap core is freezing. When I have the ac in manual mode, high fan, low temp, and set to center vents for long period of time say a couple hours, eventually the flow through the center vents becomes restricted. The air flow through the center vents is week even though the fan is still on hi and the air becomes slightly warmer than when it started. When starting the car after it has been off sitting for a few hours the air comes on cold full blast as it should be. I've checked the air filter, its fairly new and clean. I've use the foam cleaner you spray into the drain tube and it came out fairly clean. The drain isn't clogged. I hooked up my gauge set and these are the readings I got when the ac was working. I didn't have time to wait for the symptoms to occur. Any ideas?

Unfortunately I wasn't able to get techstream to work so I don't have those readings. I included screen shots.

car is off.


The next 4 are readings taken over a 30 minute period with the temp on low, fan high, ac on. first on fresh air then on circulate.





this final image is when the car was shut off