This morning on 154.3550 I am receiving P25 NAC 1A4 WyoLink Site 113 Russell Hill, Laramie, WY, 167 miles north of me. Maybe the warm weather is contributing to this?
Congratulations, Mick, and welcome to "ducting" on VHF. I have been an amateur radio operator and was a firefighter for many years. I'm aware of many instances when extraordinary distances between ham radio operators occurred during periods when "ducting" was prevalent. I also am aware of many instances when public safety radio signals (police, fire, EMS) migrated great distances as a result of "ducting." In the 1960s up until the 1980s, the Kansas City MO Fire Department and the Springfield MO Fire Department shared 154.13 MHz (I hope my memory is still accurate as to the frequency.) It was common knowledge among firefighters and dispatchers in each department that the 160 mile gap would often be bridged "when radio conditions" were just right. These folks might not have all known that they were experiencing ducting, but the results were the same: normal communications greatly expanded over a significantly larger range.
Ducting can occur with regularity and predictability when certain atmospheric conditions are present. In my personal experience during living in Missouri for 21 years, I saw a correlation between ducting and severe thunderstorm activity within the following 6-8 hours. I'm not talking about the run-of-the-mill thunderstorm. I'm referring to those with destructive consequences.
Ducting can be present on a wide range of frequencies.
There is a nice bit of information about "ducting" available at this section of Radio Reference.
https://wiki.radioreference.com/index.php/DXing_Above_30_Mhz
Thanks for sharing your catch. Your supposition that the warm weather was contributing to it is relevant in my opinion. I've only experienced ducting reception and transmissions when unusual weather conditions were predicted. Once the weather conditions changed, the ducting disappeared.
As a side note to you, the NWS issued a Blizzard Warning for Northern El Paso County from 9:00 pm today until 11:00 am tomorrow. Again, there is a correlation between the observation of radio "ducting" and predicted adverse weather.
Thanks for sharing your info here, Mick. The Colorado Radio Discussion Forum is my favorite forum on Radio Reference. I have learned a great deal during the two and a half years that I've lived in Colorado Springs.
Phil