I agree with your thinking. Being unfamiliar with the Highlands, are there any Priority Targets (military bases, 5,000ft + long runways, etc) upwind of the area?

As for indicators for Bugging out of a targeted area, I peruse several websites for news. That list covers both ends of the Reliabilty Spectrum. First indicators normally appear in the least reliable places. If there is more than one source within a short amount of time, Story Reliability increases. If the story surfaces on a moderately reliable site within 3 days, there is usually something significant about the story. If the story is true AND significant, it will show up on highly reliable sites within about 3 more days. That provides me about 6 days to evaluate the possible ramifications of that event and allows me to review and modify my planning in the meantime.

BigBen is right about listening to ShortWave Radio, IMO.