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Some Virginia cities/counties may have a Sheriff's Dept. and Police Dept. and some may not. What you heard was the county Sheriff's Dept. comms usually sourced to one of two weather conditions. The first is a "temperature inversion". Typically this is caused by unstable portions of warm air trapped between two cooler layers. The "trapped" warmer air acts as a RF reflective barrier and results in increased ground wave signal distance. These typically occur early in mornings and deteriorate as the sun rises. Infrequently they also occur in the evenings.
The second weather related propagation is an ionized atmospheric vhf E layer, which also is unstable, but typically supports RF single and double single signal "hops" from 25-60 MHz. Typically a single hop is about 1,500 air miles and a double hop 3,000 air miles. E layer signals less than 500 air miles may be referred to as "short skip" and are a rare form of E layer RF propagation. I have experienced only one using the 6 meter ham band voice frequencies (51-52 MHz.). I had a short comm of about 10 minutes with a ham in my home area in Bristol, TN 400 air miles distant in 2010. Either E layer signal can disappear within seconds and does.
I infrequently hear the MD state police on 39 MHz. with various degrees of temperature inversion strengths and suspect that was what you were experiencing. Virginia has experienced a significant number of rain cells transiting the state off and on for the past two months with significant day/night temperature change differences in some locations.
John
W4UVV
