Knowing the regional weather pattern is very helpful as a compliment to your normal analysis
Of course I'm speculating. What I like to have, as many of you know, is monthly snowfall history.
In my recent efforts to compare Chile and California, I have uncovered a few non-obvious differences in climate. I expected Santiago and Los Angeles to be very close, which they are in annual rainfall. Average temperature differences are consistent with Santiago being farther from the coast than L.A. But who would have known the following, without looking it up:
1) Santiago has more cloud cover than L.A. (despite being farther from the coast) in every month except late spring, which is well known as being disproportionately overcast here.
2) L.A. average temperature patterns fit Santiago, and quite a few other so-called Mediterranean climate cities. But L.A.'s record maximum temperatures are much higher for nearly every month. These are due to our infamous (as from the recent fires) Santa Ana winds, which must be a more unique weather phenomenon than I thought.
3) L.A.'s highest rain months are January/February. March is only a bit lower. Santiago's highest rain months are June/July. August is a noticeable drop from July, and September is barely half August. The Las Lenas monthly snow stats had a similar pattern, so spring conditions in the Andes in September are going to be much more likely than in the Sierra in March.
4) Coastal California has "offset seasons," where late spring tends to be much cooler than other climates, and late fall much warmer. I had always assumed than this was due to our cold ocean currents. But Santiago and Cape Town have even colder ocean currents and no offset seasons.
So Tina is correct that without some good snow stats it is very difficult to analyze snow conditions from afar. It is possible that western North America in general has far better snow conditions around the spring equinox than other ski regions (related in part to items 3&4 above), though high resorts in the Alps have a good reputation for March/April.
Since we don't know how much snow the Iranian mountains get, we also don't know how deep the spring snowpack is. I think a deep snowpack is needed for consistent spring snow surfaces, otherwise melting will be irregular and some places will burn off completely. I have to think this was a factor in Portillo having smooth and consistent spring snow while the Valle Nevado group with 30% less snowfall did not. Wind exposure was also a factor at Valle Nevado, as it may be in Iran.