a/c blowing cold for a while then hot

[shimmersky]

hi everyone
so im starting to feel the heat here in vegas its over 100f today
something funny started with the a/c the other day
driving along and the a/c is working fine
then all of a sudden it just starts blowing ambient air
no more cooling!!

i thought it might be a refrigerant charge issue so i purchased a bottle kit type thing with a gauge to tell you if it needs a charge or not, it says it wont read correct if it is over 85f
and it said my system was in the red or in need of mechanical service(high pressure reading at the low a/c port)

the car seems to cool just fine until it seems to just get too hot(ambient) and then somthing stops it from blowing cold air
if i let the car sit for a while and cool down(engine) and start with full a/c it seems to work fine

i know this car has a pretty unique cooling system, but does anybody have any ideas or advice
maybe i just need to take it to my tech and have the system recharged

stay cool