Fixed! I examined the radiator (and all associated tubes, etc.) area for any obvious damage from rock; there was none. I'm not a mechanic, so I looked all over the internet for common issues with Honda V6 air conditioning. Frequently, there were posts about problems with the factory relay switch (in the fuse box under the hood) for the a/c condenser clutch. So, I replaced mine (less than $7), and that seems to have fixed the issue. Nice cold a/c now!
The only other indicator of this relay "misbehaving" was a very low volume whirling noise produced at odd intervals while driving, which would go off and on. I am thinking the failed relay was part of that problem. Typo in pervioius post; my 2011 Honda Accord Crosstour!