I fear you may never 'convince' AWEKAS of the quality of your data until they have several other stations at higher elevations in your vicinity. You are probably fighting the 'law of averages', not to mention non-standard conditions for computing the value they want. Your terrain could be affecting the air temps in your location. Maybe you could offer the NWS an acre to place one of their reporting/recording systems!
When I started flying, high altitude vertical spacing was based on 2,000' separations. Now, using GPS, they use 1,000'! Too much variation in instrument capabilities, installation and air conditions! "Computers/satellites never fayle!"