Mountain flying and flying in and out of airfields in the area will be subjected to the dangers of density alt, dangerous mechanical turbulence associated with updrafts, downdrafts, horizontal and vertical rotors; decreased oxygen at alt.
Many gyros have a less than stellar rate of climb making them particularly vulnerable to the various air movements around mountainous terrain. Winds funnelling through valleys can produce pronounced higher velocities due Venturi effect.
The less stable air, due all the above, can also produce sudden fogs and decreased visibility at very short notice. When doing some single seat training at N Wales airport which is right beside a cliff and the sea, on a bright sunny day, the orographic fog could suddenly start streaming over the field. I was amazed at how quickly it shut us down, then a short while later had cleared.
As you say not a great deal of very high ground here but enough in the Lake District, Pennines, Cheviots to keep one on your toes. Over in the US plenty of very high ground. Of the over 200 highest major summits of the United States, 88 are located in Colorado, 49 in Alaska, 22 in California, 14 in Wyoming, 8 in New Mexico, 5 in Utah, 4 in Nevada, 3 in Montana, 2 in Washington, 2 in Hawaiʻi, 2 in Idaho, and 1 in Arizona and we are talking ranging from 11000’ to 20,000’.
Flying in mountainous terrain is light aircraft is a whole new area that one should learn about if flying around high ground. Even airliners have been effected. A BOAC departing Tokyo flew near Mt Fuji and was ripped apart by a rotor generated by winds round the mountain
Flight 911’s filed flight plan had called for a southerly takeoff followed by a 40-degree right turn to head southwest toward Hong Kong. The commander of flight 911before takeoff, had requested and received permission from air traffic control to make a close pass just to the east of the volcano before returning to the designated airway.
Just southeast of Mt. Fuji, 911 flew into a monstrous standing rotor caused by Fuji’s “mountain wave.” The gusts exceeded design limits subjected the plane to momentary gravitational loads in excess of +7.5G, killing some of the passengers, particularly those with seat belts unfastened. A passenger's video camera, recording at the moment of upset, malfunctioned skipped two frames under the massive G-load, then briefly captured blurred images of the cabin interior before it abruptly stopped filming.
The loads ripped off the tailfin smashing it over against the left horizontal stabilizer. The stabilizer broke away, causing the plane to pitch steeply upward the sudden pitch-up over-stressing all four engine pylons to breaking point. The engines separated from the wings, followed almost instantaneously by the empennage as far forward as the rear exit doors. As the airliner began spiraling down the wings broke up. From16,000’ the shredding airliner came down streaming fuel and smoke, then baggage and passengers until smashing into the base of the Mountain.
Later that day a US Navy Skyhawk taking part in search and rescue efforts in the area flew into the same mountain wave that had brought down the 707. Despite encountering load fluctuations ranging from -4 to +9G, the pilot managed to regain control and reported what he had encountered. Japanese investigators set up a scale model of the terrain around Mount Fuji then ran wind tunnel tests to determine what kind of turbulence might have existed on the lee side of the volcano. They found strong winds blowing over the cone created an area of unstable air extending up to 12 miles in the wake of the mountain, as well as upward from the summit to an altitude of 16,000 feet with localised wind shear within the unstable area extreme enough to rip the 707 apart.
Steve Fosset was killed while mountain and the NTSB reported the probable cause was an inadvertent encounter with downdrafts above mountainous terrain that exceeded the climb capability of the Bellanca Super Decathlon he was flying. Downdrafts, high-density altitude and mountainous terrain all contributing factors.
I’ve also seen mountain wave cloud formations extending back miles from both the Rockies and the Andes.