almost slammed it in my truck door
Looks like a member of the thorn subfamily to me, but I'm not familiar with which ones are in the US
Maybe a Orange Holomelina (Holomelina aurantiaca)?
Per Professor Adams (rhadams824):
According to Dr. Paul Opler who coauthored a book, Moths of Western North America by J.A. Powell and P.A. Opler is pretty sure that its a species of geometrid moth, Sicya macularia. The species is quite variable. It's not reported as early as April though.
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